[RFC,CABC,v2,3/3] drm/i915: CABC support for backlight control

Submitted by Deepak M on July 24, 2015, 12:24 p.m.

Details

Message ID 1437740649-9168-1-git-send-email-m.deepak@intel.com
State New
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Commit Message

Deepak M July 24, 2015, 12:24 p.m.
In CABC (Content Adaptive Brightness Control) content grey level
scale can be increased while simultaneously decreasing
brightness of the backlight to achieve same perceived brightness.

The CABC is not standardized and panel vendors are free to follow
their implementation. The CABC implementaion here assumes that the
panels use standard SW register for control.

In this design there will be no PWM signal from the SoC and DCS
commands are sent to enable and control the backlight brightness.

v2:
- Created a new backlight driver for cabc, which will be registered
  only when it cabc is supported by panel.
  (Addressed comment from Daniel Vetter)

Signed-off-by: Deepak M <m.deepak@intel.com>
---
 drivers/gpu/drm/i915/Makefile         |    1 +
 drivers/gpu/drm/i915/intel_drv.h      |    3 +-
 drivers/gpu/drm/i915/intel_dsi.c      |   13 ++
 drivers/gpu/drm/i915/intel_dsi_cabc.c |  349 +++++++++++++++++++++++++++++++++
 drivers/gpu/drm/i915/intel_dsi_cabc.h |   45 +++++
 drivers/gpu/drm/i915/intel_panel.c    |   22 ++-
 include/video/mipi_display.h          |    8 +
 7 files changed, 436 insertions(+), 5 deletions(-)
 create mode 100644 drivers/gpu/drm/i915/intel_dsi_cabc.c
 create mode 100644 drivers/gpu/drm/i915/intel_dsi_cabc.h

Patch hide | download patch | download mbox

diff --git a/drivers/gpu/drm/i915/Makefile b/drivers/gpu/drm/i915/Makefile
index de21965..a73953c 100644
--- a/drivers/gpu/drm/i915/Makefile
+++ b/drivers/gpu/drm/i915/Makefile
@@ -75,6 +75,7 @@  i915-y += dvo_ch7017.o \
 	  intel_dp_mst.o \
 	  intel_dsi.o \
 	  intel_dsi_pll.o \
+	  intel_dsi_cabc.o \
 	  intel_dsi_panel_vbt.o \
 	  intel_dvo.o \
 	  intel_hdmi.o \
diff --git a/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h
index 3f0a890..9f806dd5 100644
--- a/drivers/gpu/drm/i915/intel_drv.h
+++ b/drivers/gpu/drm/i915/intel_drv.h
@@ -1319,7 +1319,8 @@  extern struct drm_display_mode *intel_find_panel_downclock(
 				struct drm_connector *connector);
 void intel_backlight_register(struct drm_device *dev);
 void intel_backlight_unregister(struct drm_device *dev);
-
+extern int cabc_backlight_device_register(struct intel_connector *connector);
+extern void cabc_backlight_device_unregister(struct intel_connector *connector);
 
 /* intel_psr.c */
 void intel_psr_enable(struct intel_dp *intel_dp);
diff --git a/drivers/gpu/drm/i915/intel_dsi.c b/drivers/gpu/drm/i915/intel_dsi.c
index 98998e9..8f006f2 100644
--- a/drivers/gpu/drm/i915/intel_dsi.c
+++ b/drivers/gpu/drm/i915/intel_dsi.c
@@ -34,6 +34,7 @@ 
 #include "i915_drv.h"
 #include "intel_drv.h"
 #include "intel_dsi.h"
+#include "intel_dsi_cabc.h"
 
 static const struct {
 	u16 panel_id;
@@ -376,6 +377,7 @@  static void intel_dsi_enable(struct intel_encoder *encoder)
 	struct drm_device *dev = encoder->base.dev;
 	struct drm_i915_private *dev_priv = dev->dev_private;
 	struct intel_dsi *intel_dsi = enc_to_intel_dsi(&encoder->base);
+	struct intel_connector *connector = intel_dsi->attached_connector;
 	enum port port;
 
 	DRM_DEBUG_KMS("\n");
@@ -396,6 +398,9 @@  static void intel_dsi_enable(struct intel_encoder *encoder)
 
 		intel_dsi_port_enable(encoder);
 	}
+
+	if (dev_priv->vbt.dsi.config->cabc_supported)
+		cabc_enable_backlight(connector);
 }
 
 static void intel_dsi_pre_enable(struct intel_encoder *encoder)
@@ -469,11 +474,15 @@  static void intel_dsi_disable(struct intel_encoder *encoder)
 	struct drm_device *dev = encoder->base.dev;
 	struct drm_i915_private *dev_priv = dev->dev_private;
 	struct intel_dsi *intel_dsi = enc_to_intel_dsi(&encoder->base);
+	struct intel_connector *connector = intel_dsi->attached_connector;
 	enum port port;
 	u32 temp;
 
 	DRM_DEBUG_KMS("\n");
 
+	if (dev_priv->vbt.dsi.config->cabc_supported)
+		cabc_disable_backlight(connector);
+
 	if (is_vid_mode(intel_dsi)) {
 		for_each_dsi_port(port, intel_dsi->ports)
 			wait_for_dsi_fifo_empty(intel_dsi, port);
@@ -1099,6 +1108,10 @@  void intel_dsi_init(struct drm_device *dev)
 
 	intel_panel_init(&intel_connector->panel, fixed_mode, NULL);
 
+	if (dev_priv->vbt.dsi.config->cabc_supported)
+		cabc_setup_backlight(connector,
+			intel_encoder->crtc_mask ==
+				(1 << PIPE_A) ? PIPE_A : PIPE_B);
 	return;
 
 err:
diff --git a/drivers/gpu/drm/i915/intel_dsi_cabc.c b/drivers/gpu/drm/i915/intel_dsi_cabc.c
new file mode 100644
index 0000000..2a78326
--- /dev/null
+++ b/drivers/gpu/drm/i915/intel_dsi_cabc.c
@@ -0,0 +1,349 @@ 
+/*
+ * Copyright © 2006-2010 Intel Corporation
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the "Software"),
+ * to deal in the Software without restriction, including without limitation
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,
+ * and/or sell copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice (including the next
+ * paragraph) shall be included in all copies or substantial portions of the
+ * Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
+ * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+ * DEALINGS IN THE SOFTWARE.
+ *
+ */
+
+#include <linux/kernel.h>
+#include <linux/moduleparam.h>
+#include "intel_drv.h"
+#include "intel_dsi.h"
+#include "i915_drv.h"
+#include "intel_dsi_cabc.h"
+#include <video/mipi_display.h>
+#include <drm/drm_mipi_dsi.h>
+
+int cabc_setup_backlight(struct intel_connector *connector,
+		enum pipe unused)
+{
+	struct drm_device *dev = connector->base.dev;
+	struct intel_dsi *intel_dsi = NULL;
+	struct drm_crtc *crtc = NULL;
+	struct intel_encoder *encoder = NULL;
+	struct intel_panel *panel = &connector->panel;
+	struct mipi_dsi_device *dsi_device;
+	u8 level;
+
+	list_for_each_entry(crtc, &dev->mode_config.crtc_list, head) {
+		for_each_encoder_on_crtc(dev, crtc, encoder) {
+			if (encoder->type == INTEL_OUTPUT_DSI)
+				intel_dsi = enc_to_intel_dsi(&encoder->base);
+		}
+	}
+	dsi_device = intel_dsi->dsi_hosts[0]->device;
+	panel->backlight.max = CABC_MAX_VALUE;
+	panel->backlight.level = CABC_MAX_VALUE;
+	level = CABC_MAX_VALUE;
+	panel->backlight.enabled = true;
+	return 0;
+}
+
+u32 cabc_get_backlight(struct intel_connector *connector)
+{
+	struct drm_device *dev = connector->base.dev;
+	struct intel_dsi *intel_dsi = NULL;
+	struct drm_crtc *crtc = NULL;
+	struct intel_encoder *encoder = NULL;
+	struct mipi_dsi_device *dsi_device;
+	struct intel_panel *panel = &connector->panel;
+	u8 data[2] = {0};
+	enum port port = PORT_A;
+	u32 ret;
+
+	list_for_each_entry(crtc, &dev->mode_config.crtc_list, head) {
+		for_each_encoder_on_crtc(dev, crtc, encoder) {
+			if (encoder->type == INTEL_OUTPUT_DSI)
+				intel_dsi = enc_to_intel_dsi(&encoder->base);
+		}
+	}
+	if (intel_dsi->dual_link) {
+		if (intel_dsi->dl_cabc_port == CABC_PORT_A ||
+				intel_dsi->dl_cabc_port == CABC_PORT_A_AND_C)
+			port = PORT_A;
+		else if (intel_dsi->dl_cabc_port == CABC_PORT_C)
+			port = PORT_C;
+	}
+
+	dsi_device = intel_dsi->dsi_hosts[port]->device;
+	mipi_dsi_dcs_read(dsi_device, MIPI_DCS_CABC_LEVEL_RD, data, 2);
+
+	ret = (data[1] * panel->backlight.max) / 255;
+	return ret;
+}
+
+void cabc_set_backlight(struct intel_connector *connector, u32 level)
+{
+	struct drm_device *dev = connector->base.dev;
+	struct intel_dsi *intel_dsi = NULL;
+	struct drm_crtc *crtc = NULL;
+	struct intel_encoder *encoder = NULL;
+	struct mipi_dsi_device *dsi_device;
+	u8 data[2] = {0};
+	enum port port = PORT_A;
+	struct intel_panel *panel = &connector->panel;
+	u8 count = 1;
+	u32 hw_level;
+
+	list_for_each_entry(crtc, &dev->mode_config.crtc_list, head) {
+		for_each_encoder_on_crtc(dev, crtc, encoder) {
+			if (encoder->type == INTEL_OUTPUT_DSI)
+				intel_dsi = enc_to_intel_dsi(&encoder->base);
+		}
+	}
+
+	if (intel_dsi->dual_link) {
+		if (intel_dsi->dl_cabc_port == CABC_PORT_A)
+			port = PORT_A;
+		else if (intel_dsi->dl_cabc_port == CABC_PORT_C)
+			port = PORT_C;
+		else if (intel_dsi->dl_cabc_port == CABC_PORT_A_AND_C)
+			port = PORT_A;
+	}
+
+	if (intel_dsi->dual_link && intel_dsi->dl_cabc_port ==
+			CABC_PORT_A_AND_C)
+		count = 2;
+
+
+	hw_level = level % (panel->backlight.max + 1);
+	hw_level = (hw_level * 255) / panel->backlight.max;
+	panel->backlight.level = hw_level;
+
+	do {
+		dsi_device = intel_dsi->dsi_hosts[port]->device;
+		data[1] = hw_level;
+		data[0] = MIPI_DCS_CABC_LEVEL_WR;
+		mipi_dsi_dcs_write_buffer(dsi_device, data, 2);
+		if (count == 2)
+			port = PORT_C;
+	} while (--count > 0);
+}
+
+void cabc_enable_backlight(struct intel_connector *connector)
+{
+	struct drm_device *dev = connector->base.dev;
+	struct intel_dsi *intel_dsi = NULL;
+	struct drm_crtc *crtc = NULL;
+	struct intel_encoder *encoder = NULL;
+	struct intel_panel *panel = &connector->panel;
+	struct mipi_dsi_device *dsi_device;
+	enum port port = PORT_A;
+	u8 data[2] = {0};
+	u8 count = 1;
+
+	list_for_each_entry(crtc, &dev->mode_config.crtc_list, head) {
+		for_each_encoder_on_crtc(dev, crtc, encoder) {
+			if (encoder->type == INTEL_OUTPUT_DSI)
+				intel_dsi = enc_to_intel_dsi(&encoder->base);
+		}
+	}
+
+	if (intel_dsi->dual_link) {
+		if (intel_dsi->dl_cabc_port == CABC_PORT_A)
+			port = PORT_A;
+		else if (intel_dsi->dl_cabc_port == CABC_PORT_C)
+			port = PORT_C;
+		else if (intel_dsi->dl_cabc_port == CABC_PORT_A_AND_C)
+			port = PORT_A;
+	}
+
+	if (intel_dsi->dual_link && intel_dsi->dl_cabc_port ==
+			CABC_PORT_A_AND_C)
+		count = 2;
+
+	do {
+		dsi_device = intel_dsi->dsi_hosts[port]->device;
+
+
+		data[0] = MIPI_DCS_CABC_CONTROL_BRIGHT_WR;
+		data[1] = CABC_BACKLIGHT | CABC_DIMMING_DISPLAY | CABC_BCTRL;
+		mipi_dsi_dcs_write_buffer(dsi_device, data, 2);
+		data[0] = MIPI_DCS_CABC_CONTROL_WR;
+		data[1] = CABC_VIDEO_MODE;
+		mipi_dsi_dcs_write_buffer(dsi_device, data, 2);
+
+		if (count == 2)
+			port = PORT_C;
+	} while (--count > 0);
+
+	cabc_set_backlight(connector, panel->backlight.level);
+}
+
+void cabc_disable_backlight(struct intel_connector *connector)
+{
+	struct drm_device *dev = connector->base.dev;
+	struct intel_dsi *intel_dsi = NULL;
+	struct drm_crtc *crtc = NULL;
+	struct intel_encoder *encoder = NULL;
+	struct mipi_dsi_device *dsi_device;
+	enum port port = PORT_A;
+	u8 data[2] = {0};
+	u8 count = 1;
+
+	list_for_each_entry(crtc, &dev->mode_config.crtc_list, head) {
+		for_each_encoder_on_crtc(dev, crtc, encoder) {
+			if (encoder->type == INTEL_OUTPUT_DSI)
+				intel_dsi = enc_to_intel_dsi(&encoder->base);
+		}
+	}
+
+	if (intel_dsi->dual_link) {
+		if (intel_dsi->dl_cabc_port == CABC_PORT_A)
+			port = PORT_A;
+		else if (intel_dsi->dl_cabc_port == CABC_PORT_C)
+			port = PORT_C;
+		else if (intel_dsi->dl_cabc_port == CABC_PORT_A_AND_C)
+			port = PORT_A;
+	}
+
+	if (intel_dsi->dual_link && intel_dsi->dl_cabc_port ==
+			CABC_PORT_A_AND_C)
+		count = 2;
+
+	do {
+		dsi_device = intel_dsi->dsi_hosts[port]->device;
+
+		cabc_set_backlight(connector, 0);
+		data[1] = CABC_OFF;
+		data[0] = MIPI_DCS_CABC_CONTROL_WR;
+		mipi_dsi_dcs_write_buffer(dsi_device, data, 2);
+		data[0] = MIPI_DCS_CABC_CONTROL_BRIGHT_WR;
+		mipi_dsi_dcs_write_buffer(dsi_device, data, 2);
+
+		if (count == 2)
+			port = PORT_C;
+	} while (--count > 0);
+}
+
+static int cabc_backlight_device_update_status(struct backlight_device *bd)
+{
+	struct intel_connector *connector = bl_get_data(bd);
+	struct intel_panel *panel = &connector->panel;
+	struct drm_device *dev = connector->base.dev;
+
+	drm_modeset_lock(&dev->mode_config.connection_mutex, NULL);
+	DRM_DEBUG_KMS("updating intel_backlight, brightness=%d/%d\n",
+			bd->props.brightness, bd->props.max_brightness);
+	cabc_set_backlight(connector, bd->props.brightness);
+
+	/*
+	 * Allow flipping bl_power as a sub-state of enabled. Sadly the
+	 * backlight class device does not make it easy to to differentiate
+	 * between callbacks for brightness and bl_power, so our backlight_power
+	 * callback needs to take this into account.
+	 */
+	if (panel->backlight.enabled) {
+		if (panel->backlight_power) {
+			bool enable = bd->props.power == FB_BLANK_UNBLANK &&
+				bd->props.brightness != 0;
+			panel->backlight_power(connector, enable);
+		}
+	} else {
+		bd->props.power = FB_BLANK_POWERDOWN;
+	}
+
+	drm_modeset_unlock(&dev->mode_config.connection_mutex);
+	return 0;
+}
+
+static int cabc_backlight_device_get_brightness(struct backlight_device *bd)
+{
+	struct intel_connector *connector = bl_get_data(bd);
+	struct drm_device *dev = connector->base.dev;
+	struct drm_i915_private *dev_priv = dev->dev_private;
+	int ret;
+
+	intel_runtime_pm_get(dev_priv);
+	drm_modeset_lock(&dev->mode_config.connection_mutex, NULL);
+
+	ret = cabc_get_backlight(connector);
+
+	drm_modeset_unlock(&dev->mode_config.connection_mutex);
+	intel_runtime_pm_put(dev_priv);
+
+	return ret;
+}
+
+static const struct backlight_ops cabc_backlight_device_ops = {
+	.update_status = cabc_backlight_device_update_status,
+	.get_brightness = cabc_backlight_device_get_brightness,
+};
+
+int cabc_backlight_device_register(struct intel_connector *connector)
+{
+	struct intel_panel *panel = &connector->panel;
+	struct backlight_properties props;
+
+	if (WARN_ON(panel->backlight.device))
+		return -ENODEV;
+
+	if (!panel->backlight.present)
+		return 0;
+
+	WARN_ON(panel->backlight.max == 0);
+
+	memset(&props, 0, sizeof(props));
+	props.type = BACKLIGHT_FIRMWARE;
+
+	/*
+	 * Note: Everything should work even if the backlight device max
+	 * presented to the userspace is arbitrarily chosen.
+	 */
+	props.max_brightness = panel->backlight.max;
+	props.brightness = props.max_brightness;
+
+	if (panel->backlight.enabled)
+		props.power = FB_BLANK_UNBLANK;
+	else
+		props.power = FB_BLANK_POWERDOWN;
+
+	/*
+	 * Note: using the same name independent of the connector prevents
+	 * registration of multiple backlight devices in the driver.
+	 */
+	panel->backlight.device =
+		backlight_device_register("intel_backlight",
+				connector->base.kdev,
+				connector,
+				&cabc_backlight_device_ops, &props);
+
+	if (IS_ERR(panel->backlight.device)) {
+		DRM_ERROR("Failed to register backlight: %ld\n",
+				PTR_ERR(panel->backlight.device));
+		panel->backlight.device = NULL;
+		return -ENODEV;
+	}
+
+	DRM_DEBUG_KMS("Connector %s backlight sysfs interface registered\n",
+			connector->base.name);
+
+	return 0;
+}
+
+void cabc_backlight_device_unregister(struct intel_connector *connector)
+{
+	struct intel_panel *panel = &connector->panel;
+
+	if (panel->backlight.device) {
+		backlight_device_unregister(panel->backlight.device);
+		panel->backlight.device = NULL;
+	}
+}
diff --git a/drivers/gpu/drm/i915/intel_dsi_cabc.h b/drivers/gpu/drm/i915/intel_dsi_cabc.h
new file mode 100644
index 0000000..5d134f5
--- /dev/null
+++ b/drivers/gpu/drm/i915/intel_dsi_cabc.h
@@ -0,0 +1,45 @@ 
+/*
+ * Copyright © 2013 Intel Corporation
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the "Software"),
+ * to deal in the Software without restriction, including without limitation
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,
+ * and/or sell copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice (including the next
+ * paragraph) shall be included in all copies or substantial portions of the
+ * Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
+ * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+ * DEALINGS IN THE SOFTWARE.
+ *
+ */
+
+extern int cabc_backlight_device_register(struct intel_connector *connector);
+extern void cabc_backlight_device_unregister(struct intel_connector *connector);
+void cabc_set_backlight(struct intel_connector *connector, u32 level);
+u32 cabc_get_backlight(struct intel_connector *connector);
+void cabc_enable_backlight(struct intel_connector *connector);
+void cabc_disable_backlight(struct intel_connector *connector);
+int cabc_setup_backlight(struct intel_connector *connector, enum pipe unused);
+
+#define CABC_OFF                       (0 << 0)
+#define CABC_USER_INTERFACE_IMAGE      (1 << 0)
+#define CABC_STILL_PICTURE             (2 << 0)
+#define CABC_VIDEO_MODE                        (3 << 0)
+
+#define CABC_BACKLIGHT                 (1 << 2)
+#define CABC_DIMMING_DISPLAY           (1 << 3)
+#define CABC_BCTRL                     (1 << 5)
+
+#define CABC_PORT_A                    0x00
+#define CABC_PORT_C                    0x01
+#define CABC_PORT_A_AND_C              0x02
+#define CABC_MAX_VALUE		       0xff
diff --git a/drivers/gpu/drm/i915/intel_panel.c b/drivers/gpu/drm/i915/intel_panel.c
index 55aad23..c73449b 100644
--- a/drivers/gpu/drm/i915/intel_panel.c
+++ b/drivers/gpu/drm/i915/intel_panel.c
@@ -1502,15 +1502,29 @@  void intel_panel_fini(struct intel_panel *panel)
 void intel_backlight_register(struct drm_device *dev)
 {
 	struct intel_connector *connector;
+	struct drm_i915_private *dev_priv = dev->dev_private;
 
-	list_for_each_entry(connector, &dev->mode_config.connector_list, base.head)
-		intel_backlight_device_register(connector);
+	list_for_each_entry(connector, &dev->mode_config.connector_list,
+					base.head) {
+		if (connector->encoder->type == INTEL_OUTPUT_DSI &&
+			dev_priv->vbt.dsi.config->cabc_supported)
+			cabc_backlight_device_register(connector);
+		else
+			intel_backlight_device_register(connector);
+	}
 }
 
 void intel_backlight_unregister(struct drm_device *dev)
 {
 	struct intel_connector *connector;
+	struct drm_i915_private *dev_priv = dev->dev_private;
 
-	list_for_each_entry(connector, &dev->mode_config.connector_list, base.head)
-		intel_backlight_device_unregister(connector);
+	list_for_each_entry(connector, &dev->mode_config.connector_list,
+					base.head) {
+		if (connector->encoder->type == INTEL_OUTPUT_DSI &&
+			dev_priv->vbt.dsi.config->cabc_supported)
+			cabc_backlight_device_unregister(connector);
+		else
+			intel_backlight_device_unregister(connector);
+	}
 }
diff --git a/include/video/mipi_display.h b/include/video/mipi_display.h
index ddcc8ca..5b8eeec 100644
--- a/include/video/mipi_display.h
+++ b/include/video/mipi_display.h
@@ -117,6 +117,14 @@  enum {
 	MIPI_DCS_GET_SCANLINE		= 0x45,
 	MIPI_DCS_READ_DDB_START		= 0xA1,
 	MIPI_DCS_READ_DDB_CONTINUE	= 0xA8,
+	MIPI_DCS_CABC_LEVEL_RD          = 0x52,
+	MIPI_DCS_CABC_MIN_BRIGHTNESS_RD = 0x5F,
+	MIPI_DCS_CABC_CONTROL_RD        = 0x56,
+	MIPI_DCS_CABC_CONTROL_BRIGHT_RD = 0x54,
+	MIPI_DCS_CABC_LEVEL_WR          = 0x51,
+	MIPI_DCS_CABC_MIN_BRIGHTNESS_WR = 0x5E,
+	MIPI_DCS_CABC_CONTROL_WR        = 0x55,
+	MIPI_DCS_CABC_CONTROL_BRIGHT_WR = 0x53,
 };
 
 /* MIPI DCS pixel formats */

Comments

On 7/24/2015 5:54 PM, Deepak M wrote:
> In CABC (Content Adaptive Brightness Control) content grey level
> scale can be increased while simultaneously decreasing
> brightness of the backlight to achieve same perceived brightness.
>
> The CABC is not standardized and panel vendors are free to follow
> their implementation. The CABC implementaion here assumes that the
> panels use standard SW register for control.
>
> In this design there will be no PWM signal from the SoC and DCS
> commands are sent to enable and control the backlight brightness.
>
> v2:
> - Created a new backlight driver for cabc, which will be registered
>    only when it cabc is supported by panel.
>    (Addressed comment from Daniel Vetter)
>
> Signed-off-by: Deepak M <m.deepak@intel.com>
> ---
>   drivers/gpu/drm/i915/Makefile         |    1 +
>   drivers/gpu/drm/i915/intel_drv.h      |    3 +-
>   drivers/gpu/drm/i915/intel_dsi.c      |   13 ++
>   drivers/gpu/drm/i915/intel_dsi_cabc.c |  349 +++++++++++++++++++++++++++++++++
>   drivers/gpu/drm/i915/intel_dsi_cabc.h |   45 +++++
>   drivers/gpu/drm/i915/intel_panel.c    |   22 ++-
>   include/video/mipi_display.h          |    8 +
>   7 files changed, 436 insertions(+), 5 deletions(-)
>   create mode 100644 drivers/gpu/drm/i915/intel_dsi_cabc.c
>   create mode 100644 drivers/gpu/drm/i915/intel_dsi_cabc.h
>
> diff --git a/drivers/gpu/drm/i915/Makefile b/drivers/gpu/drm/i915/Makefile
> index de21965..a73953c 100644
> --- a/drivers/gpu/drm/i915/Makefile
> +++ b/drivers/gpu/drm/i915/Makefile
> @@ -75,6 +75,7 @@ i915-y += dvo_ch7017.o \
>   	  intel_dp_mst.o \
>   	  intel_dsi.o \
>   	  intel_dsi_pll.o \
> +	  intel_dsi_cabc.o \
>   	  intel_dsi_panel_vbt.o \
>   	  intel_dvo.o \
>   	  intel_hdmi.o \
> diff --git a/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h
> index 3f0a890..9f806dd5 100644
> --- a/drivers/gpu/drm/i915/intel_drv.h
> +++ b/drivers/gpu/drm/i915/intel_drv.h
> @@ -1319,7 +1319,8 @@ extern struct drm_display_mode *intel_find_panel_downclock(
>   				struct drm_connector *connector);
>   void intel_backlight_register(struct drm_device *dev);
>   void intel_backlight_unregister(struct drm_device *dev);
> -
> +extern int cabc_backlight_device_register(struct intel_connector *connector);
> +extern void cabc_backlight_device_unregister(struct intel_connector *connector);
>   
>   /* intel_psr.c */
>   void intel_psr_enable(struct intel_dp *intel_dp);
> diff --git a/drivers/gpu/drm/i915/intel_dsi.c b/drivers/gpu/drm/i915/intel_dsi.c
> index 98998e9..8f006f2 100644
> --- a/drivers/gpu/drm/i915/intel_dsi.c
> +++ b/drivers/gpu/drm/i915/intel_dsi.c
> @@ -34,6 +34,7 @@
>   #include "i915_drv.h"
>   #include "intel_drv.h"
>   #include "intel_dsi.h"
> +#include "intel_dsi_cabc.h"
>   
>   static const struct {
>   	u16 panel_id;
> @@ -376,6 +377,7 @@ static void intel_dsi_enable(struct intel_encoder *encoder)
>   	struct drm_device *dev = encoder->base.dev;
>   	struct drm_i915_private *dev_priv = dev->dev_private;
>   	struct intel_dsi *intel_dsi = enc_to_intel_dsi(&encoder->base);
> +	struct intel_connector *connector = intel_dsi->attached_connector;
>   	enum port port;
>   
>   	DRM_DEBUG_KMS("\n");
> @@ -396,6 +398,9 @@ static void intel_dsi_enable(struct intel_encoder *encoder)
>   
>   		intel_dsi_port_enable(encoder);
>   	}
> +
> +	if (dev_priv->vbt.dsi.config->cabc_supported)
> +		cabc_enable_backlight(connector);
>   }
>   
>   static void intel_dsi_pre_enable(struct intel_encoder *encoder)
> @@ -469,11 +474,15 @@ static void intel_dsi_disable(struct intel_encoder *encoder)
>   	struct drm_device *dev = encoder->base.dev;
>   	struct drm_i915_private *dev_priv = dev->dev_private;
>   	struct intel_dsi *intel_dsi = enc_to_intel_dsi(&encoder->base);
> +	struct intel_connector *connector = intel_dsi->attached_connector;
>   	enum port port;
>   	u32 temp;
>   
>   	DRM_DEBUG_KMS("\n");
>   
> +	if (dev_priv->vbt.dsi.config->cabc_supported)
> +		cabc_disable_backlight(connector);
> +
>   	if (is_vid_mode(intel_dsi)) {
>   		for_each_dsi_port(port, intel_dsi->ports)
>   			wait_for_dsi_fifo_empty(intel_dsi, port);
> @@ -1099,6 +1108,10 @@ void intel_dsi_init(struct drm_device *dev)
>   
>   	intel_panel_init(&intel_connector->panel, fixed_mode, NULL);
>   
> +	if (dev_priv->vbt.dsi.config->cabc_supported)
> +		cabc_setup_backlight(connector,
> +			intel_encoder->crtc_mask ==
> +				(1 << PIPE_A) ? PIPE_A : PIPE_B);
>   	return;
>   
>   err:
> diff --git a/drivers/gpu/drm/i915/intel_dsi_cabc.c b/drivers/gpu/drm/i915/intel_dsi_cabc.c
> new file mode 100644
> index 0000000..2a78326
> --- /dev/null
> +++ b/drivers/gpu/drm/i915/intel_dsi_cabc.c
> @@ -0,0 +1,349 @@
> +/*
> + * Copyright © 2006-2010 Intel Corporation
> + *
> + * Permission is hereby granted, free of charge, to any person obtaining a
> + * copy of this software and associated documentation files (the "Software"),
> + * to deal in the Software without restriction, including without limitation
> + * the rights to use, copy, modify, merge, publish, distribute, sublicense,
> + * and/or sell copies of the Software, and to permit persons to whom the
> + * Software is furnished to do so, subject to the following conditions:
> + *
> + * The above copyright notice and this permission notice (including the next
> + * paragraph) shall be included in all copies or substantial portions of the
> + * Software.
> + *
> + * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
> + * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
> + * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
> + * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
> + * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
> + * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
> + * DEALINGS IN THE SOFTWARE.
> + *
> + */
> +
> +#include <linux/kernel.h>
> +#include <linux/moduleparam.h>
> +#include "intel_drv.h"
> +#include "intel_dsi.h"
> +#include "i915_drv.h"
> +#include "intel_dsi_cabc.h"
> +#include <video/mipi_display.h>
> +#include <drm/drm_mipi_dsi.h>
> +
> +int cabc_setup_backlight(struct intel_connector *connector,
> +		enum pipe unused)
> +{
> +	struct drm_device *dev = connector->base.dev;
> +	struct intel_dsi *intel_dsi = NULL;
> +	struct drm_crtc *crtc = NULL;
> +	struct intel_encoder *encoder = NULL;
> +	struct intel_panel *panel = &connector->panel;
> +	struct mipi_dsi_device *dsi_device;
> +	u8 level;
> +
> +	list_for_each_entry(crtc, &dev->mode_config.crtc_list, head) {
> +		for_each_encoder_on_crtc(dev, crtc, encoder) {
> +			if (encoder->type == INTEL_OUTPUT_DSI)
> +				intel_dsi = enc_to_intel_dsi(&encoder->base);
> +		}
> +	}
> +	dsi_device = intel_dsi->dsi_hosts[0]->device;
This will work only for MIPI Port A not for MIPI Port C. Use 
for_each_dsi_port macro and intel_dsi->dsi_hosts[port] to correctly 
reach to mipi_dsi_device for both ports. If it is dual link, break after 
the completion of the first iteration.
> +	panel->backlight.max = CABC_MAX_VALUE;
> +	panel->backlight.level = CABC_MAX_VALUE;
> +	level = CABC_MAX_VALUE;
> +	panel->backlight.enabled = true;
> +	return 0;
> +}
> +
> +u32 cabc_get_backlight(struct intel_connector *connector)
> +{
> +	struct drm_device *dev = connector->base.dev;
> +	struct intel_dsi *intel_dsi = NULL;
> +	struct drm_crtc *crtc = NULL;
> +	struct intel_encoder *encoder = NULL;
> +	struct mipi_dsi_device *dsi_device;
> +	struct intel_panel *panel = &connector->panel;
> +	u8 data[2] = {0};
> +	enum port port = PORT_A;
will fail for single link MIPI Port C.
> +	u32 ret;
> +
> +	list_for_each_entry(crtc, &dev->mode_config.crtc_list, head) {
> +		for_each_encoder_on_crtc(dev, crtc, encoder) {
> +			if (encoder->type == INTEL_OUTPUT_DSI)
> +				intel_dsi = enc_to_intel_dsi(&encoder->base);
> +		}
> +	}
> +	if (intel_dsi->dual_link) {
Put the below or required logic into static inline function returning 
enum port .
> +		if (intel_dsi->dl_cabc_port == CABC_PORT_A ||
> +				intel_dsi->dl_cabc_port == CABC_PORT_A_AND_C)
> +			port = PORT_A;
> +		else if (intel_dsi->dl_cabc_port == CABC_PORT_C)
> +			port = PORT_C;
> +	}
Use for_each_dsi_port macro here . call the  inline function within 
for_each_dsi_port macro to get the required enum port for dual link.
> +
> +	dsi_device = intel_dsi->dsi_hosts[port]->device;
> +	mipi_dsi_dcs_read(dsi_device, MIPI_DCS_CABC_LEVEL_RD, data, 2);
> +
> +	ret = (data[1] * panel->backlight.max) / 255;
> +	return ret;
> +}
> +
> +void cabc_set_backlight(struct intel_connector *connector, u32 level)
> +{
> +	struct drm_device *dev = connector->base.dev;
> +	struct intel_dsi *intel_dsi = NULL;
> +	struct drm_crtc *crtc = NULL;
> +	struct intel_encoder *encoder = NULL;
> +	struct mipi_dsi_device *dsi_device;
> +	u8 data[2] = {0};
> +	enum port port = PORT_A;
> +	struct intel_panel *panel = &connector->panel;
> +	u8 count = 1;
> +	u32 hw_level;
> +
> +	list_for_each_entry(crtc, &dev->mode_config.crtc_list, head) {
> +		for_each_encoder_on_crtc(dev, crtc, encoder) {
> +			if (encoder->type == INTEL_OUTPUT_DSI)
> +				intel_dsi = enc_to_intel_dsi(&encoder->base);
> +		}
> +	}
> +
> +	if (intel_dsi->dual_link) {
Put the below logic into static inline function returning enum port .
> +		if (intel_dsi->dl_cabc_port == CABC_PORT_A)
> +			port = PORT_A;
> +		else if (intel_dsi->dl_cabc_port == CABC_PORT_C)
> +			port = PORT_C;
> +		else if (intel_dsi->dl_cabc_port == CABC_PORT_A_AND_C)
> +			port = PORT_A;
> +	}
> +
Below part not required. use for_each_dsi_port macro.
> +	if (intel_dsi->dual_link && intel_dsi->dl_cabc_port ==
> +			CABC_PORT_A_AND_C)
> +		count = 2;
> +
> +
> +	hw_level = level % (panel->backlight.max + 1);
> +	hw_level = (hw_level * 255) / panel->backlight.max;
> +	panel->backlight.level = hw_level;
> +
Use for_each_dsi_port macro as explained above.
> +	do {
> +		dsi_device = intel_dsi->dsi_hosts[port]->device;
> +		data[1] = hw_level;
> +		data[0] = MIPI_DCS_CABC_LEVEL_WR;
> +		mipi_dsi_dcs_write_buffer(dsi_device, data, 2);
> +		if (count == 2)
> +			port = PORT_C;
> +	} while (--count > 0);
> +}
> +
> +void cabc_enable_backlight(struct intel_connector *connector)
> +{
> +	struct drm_device *dev = connector->base.dev;
> +	struct intel_dsi *intel_dsi = NULL;
> +	struct drm_crtc *crtc = NULL;
> +	struct intel_encoder *encoder = NULL;
> +	struct intel_panel *panel = &connector->panel;
> +	struct mipi_dsi_device *dsi_device;
> +	enum port port = PORT_A;
Will fail for single link Port C
> +	u8 data[2] = {0};
> +	u8 count = 1;
> +
> +	list_for_each_entry(crtc, &dev->mode_config.crtc_list, head) {
> +		for_each_encoder_on_crtc(dev, crtc, encoder) {
> +			if (encoder->type == INTEL_OUTPUT_DSI)
> +				intel_dsi = enc_to_intel_dsi(&encoder->base);
> +		}
> +	}
> +
> +	if (intel_dsi->dual_link) {
Same comment .Put the below logic into static inline function returning 
enum port .
> +		if (intel_dsi->dl_cabc_port == CABC_PORT_A)
> +			port = PORT_A;
> +		else if (intel_dsi->dl_cabc_port == CABC_PORT_C)
> +			port = PORT_C;
Also below condition need not be taken into the inline function. Since 
it is dual link and with other conditions are met, then 
CABC_PORT_A_AND_C will be automatically taken care for both ports by the 
for_each_dsi_port macro.
Within for_each_dsi_port, just check for intel_dsi->dl_cabc_port != 
CABC_PORT_A_AND_C, if yes call the inline function to get the port no 
and if no, all other conditions will be taken care for both ports by 
for_each_dsi_port.
Before the end of for_each_dsi_port ,you may require to check the 
intel_dsi->dl_cabc_port != CABC_PORT_A_AND_C , so that you can return 
from the macro.
> +		else if (intel_dsi->dl_cabc_port == CABC_PORT_A_AND_C)
> +			port = PORT_A;
> +	}
> +
> +	if (intel_dsi->dual_link && intel_dsi->dl_cabc_port ==
> +			CABC_PORT_A_AND_C)
> +		count = 2;
> +
> +	do {
same comment as above. Use for_each_dsi_port
> +		dsi_device = intel_dsi->dsi_hosts[port]->device;
> +
> +
> +		data[0] = MIPI_DCS_CABC_CONTROL_BRIGHT_WR;
> +		data[1] = CABC_BACKLIGHT | CABC_DIMMING_DISPLAY | CABC_BCTRL;
> +		mipi_dsi_dcs_write_buffer(dsi_device, data, 2);
> +		data[0] = MIPI_DCS_CABC_CONTROL_WR;
> +		data[1] = CABC_VIDEO_MODE;
> +		mipi_dsi_dcs_write_buffer(dsi_device, data, 2);
> +
> +		if (count == 2)
> +			port = PORT_C;
> +	} while (--count > 0);
> +
> +	cabc_set_backlight(connector, panel->backlight.level);
> +}
> +
> +void cabc_disable_backlight(struct intel_connector *connector)
> +{
> +	struct drm_device *dev = connector->base.dev;
> +	struct intel_dsi *intel_dsi = NULL;
> +	struct drm_crtc *crtc = NULL;
> +	struct intel_encoder *encoder = NULL;
> +	struct mipi_dsi_device *dsi_device;
> +	enum port port = PORT_A;
Will fail for single link Port C
> +	u8 data[2] = {0};
> +	u8 count = 1;
> +
> +	list_for_each_entry(crtc, &dev->mode_config.crtc_list, head) {
> +		for_each_encoder_on_crtc(dev, crtc, encoder) {
> +			if (encoder->type == INTEL_OUTPUT_DSI)
> +				intel_dsi = enc_to_intel_dsi(&encoder->base);
> +		}
> +	}
> +
> +	if (intel_dsi->dual_link) {
Same comment as above. Use static inline function for this.
> +		if (intel_dsi->dl_cabc_port == CABC_PORT_A)
> +			port = PORT_A;
> +		else if (intel_dsi->dl_cabc_port == CABC_PORT_C)
> +			port = PORT_C;
> +		else if (intel_dsi->dl_cabc_port == CABC_PORT_A_AND_C)
> +			port = PORT_A;
> +	}
> +
> +	if (intel_dsi->dual_link && intel_dsi->dl_cabc_port ==
> +			CABC_PORT_A_AND_C)
> +		count = 2;
> +
> +	do {
Use for_each_dsi_port macro
> +		dsi_device = intel_dsi->dsi_hosts[port]->device;
> +
> +		cabc_set_backlight(connector, 0);
> +		data[1] = CABC_OFF;
> +		data[0] = MIPI_DCS_CABC_CONTROL_WR;
> +		mipi_dsi_dcs_write_buffer(dsi_device, data, 2);
> +		data[0] = MIPI_DCS_CABC_CONTROL_BRIGHT_WR;
> +		mipi_dsi_dcs_write_buffer(dsi_device, data, 2);
> +
> +		if (count == 2)
> +			port = PORT_C;
> +	} while (--count > 0);
> +}
> +
> +static int cabc_backlight_device_update_status(struct backlight_device *bd)
> +{
> +	struct intel_connector *connector = bl_get_data(bd);
> +	struct intel_panel *panel = &connector->panel;
> +	struct drm_device *dev = connector->base.dev;
> +
> +	drm_modeset_lock(&dev->mode_config.connection_mutex, NULL);
> +	DRM_DEBUG_KMS("updating intel_backlight, brightness=%d/%d\n",
> +			bd->props.brightness, bd->props.max_brightness);
> +	cabc_set_backlight(connector, bd->props.brightness);
> +
> +	/*
> +	 * Allow flipping bl_power as a sub-state of enabled. Sadly the
> +	 * backlight class device does not make it easy to to differentiate
> +	 * between callbacks for brightness and bl_power, so our backlight_power
> +	 * callback needs to take this into account.
> +	 */
> +	if (panel->backlight.enabled) {
> +		if (panel->backlight_power) {
> +			bool enable = bd->props.power == FB_BLANK_UNBLANK &&
> +				bd->props.brightness != 0;
> +			panel->backlight_power(connector, enable);
> +		}
> +	} else {
> +		bd->props.power = FB_BLANK_POWERDOWN;
> +	}
> +
> +	drm_modeset_unlock(&dev->mode_config.connection_mutex);
> +	return 0;
> +}
> +
> +static int cabc_backlight_device_get_brightness(struct backlight_device *bd)
> +{
> +	struct intel_connector *connector = bl_get_data(bd);
> +	struct drm_device *dev = connector->base.dev;
> +	struct drm_i915_private *dev_priv = dev->dev_private;
> +	int ret;
> +
> +	intel_runtime_pm_get(dev_priv);
> +	drm_modeset_lock(&dev->mode_config.connection_mutex, NULL);
> +
> +	ret = cabc_get_backlight(connector);
> +
> +	drm_modeset_unlock(&dev->mode_config.connection_mutex);
> +	intel_runtime_pm_put(dev_priv);
> +
> +	return ret;
> +}
> +
> +static const struct backlight_ops cabc_backlight_device_ops = {
> +	.update_status = cabc_backlight_device_update_status,
> +	.get_brightness = cabc_backlight_device_get_brightness,
> +};
> +
> +int cabc_backlight_device_register(struct intel_connector *connector)
> +{
> +	struct intel_panel *panel = &connector->panel;
> +	struct backlight_properties props;
> +
> +	if (WARN_ON(panel->backlight.device))
> +		return -ENODEV;
> +
> +	if (!panel->backlight.present)
> +		return 0;
> +
> +	WARN_ON(panel->backlight.max == 0);
> +
> +	memset(&props, 0, sizeof(props));
> +	props.type = BACKLIGHT_FIRMWARE;
> +
> +	/*
> +	 * Note: Everything should work even if the backlight device max
> +	 * presented to the userspace is arbitrarily chosen.
> +	 */
> +	props.max_brightness = panel->backlight.max;
> +	props.brightness = props.max_brightness;
> +
> +	if (panel->backlight.enabled)
> +		props.power = FB_BLANK_UNBLANK;
> +	else
> +		props.power = FB_BLANK_POWERDOWN;
> +
> +	/*
> +	 * Note: using the same name independent of the connector prevents
> +	 * registration of multiple backlight devices in the driver.
> +	 */
> +	panel->backlight.device =
> +		backlight_device_register("intel_backlight",
> +				connector->base.kdev,
> +				connector,
> +				&cabc_backlight_device_ops, &props);
> +
> +	if (IS_ERR(panel->backlight.device)) {
> +		DRM_ERROR("Failed to register backlight: %ld\n",
> +				PTR_ERR(panel->backlight.device));
> +		panel->backlight.device = NULL;
> +		return -ENODEV;
> +	}
> +
> +	DRM_DEBUG_KMS("Connector %s backlight sysfs interface registered\n",
> +			connector->base.name);
> +
> +	return 0;
> +}
> +
> +void cabc_backlight_device_unregister(struct intel_connector *connector)
> +{
> +	struct intel_panel *panel = &connector->panel;
> +
> +	if (panel->backlight.device) {
> +		backlight_device_unregister(panel->backlight.device);
> +		panel->backlight.device = NULL;
> +	}
> +}
> diff --git a/drivers/gpu/drm/i915/intel_dsi_cabc.h b/drivers/gpu/drm/i915/intel_dsi_cabc.h
> new file mode 100644
> index 0000000..5d134f5
> --- /dev/null
> +++ b/drivers/gpu/drm/i915/intel_dsi_cabc.h
> @@ -0,0 +1,45 @@
> +/*
> + * Copyright © 2013 Intel Corporation
> + *
> + * Permission is hereby granted, free of charge, to any person obtaining a
> + * copy of this software and associated documentation files (the "Software"),
> + * to deal in the Software without restriction, including without limitation
> + * the rights to use, copy, modify, merge, publish, distribute, sublicense,
> + * and/or sell copies of the Software, and to permit persons to whom the
> + * Software is furnished to do so, subject to the following conditions:
> + *
> + * The above copyright notice and this permission notice (including the next
> + * paragraph) shall be included in all copies or substantial portions of the
> + * Software.
> + *
> + * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
> + * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
> + * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
> + * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
> + * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
> + * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
> + * DEALINGS IN THE SOFTWARE.
> + *
> + */
> +
> +extern int cabc_backlight_device_register(struct intel_connector *connector);
> +extern void cabc_backlight_device_unregister(struct intel_connector *connector);
> +void cabc_set_backlight(struct intel_connector *connector, u32 level);
> +u32 cabc_get_backlight(struct intel_connector *connector);
> +void cabc_enable_backlight(struct intel_connector *connector);
> +void cabc_disable_backlight(struct intel_connector *connector);
> +int cabc_setup_backlight(struct intel_connector *connector, enum pipe unused);
> +
> +#define CABC_OFF                       (0 << 0)
> +#define CABC_USER_INTERFACE_IMAGE      (1 << 0)
> +#define CABC_STILL_PICTURE             (2 << 0)
> +#define CABC_VIDEO_MODE                        (3 << 0)
> +
> +#define CABC_BACKLIGHT                 (1 << 2)
> +#define CABC_DIMMING_DISPLAY           (1 << 3)
> +#define CABC_BCTRL                     (1 << 5)
> +
> +#define CABC_PORT_A                    0x00
> +#define CABC_PORT_C                    0x01
> +#define CABC_PORT_A_AND_C              0x02
> +#define CABC_MAX_VALUE		       0xff
> diff --git a/drivers/gpu/drm/i915/intel_panel.c b/drivers/gpu/drm/i915/intel_panel.c
> index 55aad23..c73449b 100644
> --- a/drivers/gpu/drm/i915/intel_panel.c
> +++ b/drivers/gpu/drm/i915/intel_panel.c
> @@ -1502,15 +1502,29 @@ void intel_panel_fini(struct intel_panel *panel)
>   void intel_backlight_register(struct drm_device *dev)
>   {
>   	struct intel_connector *connector;
> +	struct drm_i915_private *dev_priv = dev->dev_private;
>   
> -	list_for_each_entry(connector, &dev->mode_config.connector_list, base.head)
> -		intel_backlight_device_register(connector);
> +	list_for_each_entry(connector, &dev->mode_config.connector_list,
> +					base.head) {
> +		if (connector->encoder->type == INTEL_OUTPUT_DSI &&
> +			dev_priv->vbt.dsi.config->cabc_supported)
> +			cabc_backlight_device_register(connector);
> +		else
> +			intel_backlight_device_register(connector);
> +	}
>   }
>   
>   void intel_backlight_unregister(struct drm_device *dev)
>   {
>   	struct intel_connector *connector;
> +	struct drm_i915_private *dev_priv = dev->dev_private;
>   
> -	list_for_each_entry(connector, &dev->mode_config.connector_list, base.head)
> -		intel_backlight_device_unregister(connector);
> +	list_for_each_entry(connector, &dev->mode_config.connector_list,
> +					base.head) {
> +		if (connector->encoder->type == INTEL_OUTPUT_DSI &&
> +			dev_priv->vbt.dsi.config->cabc_supported)
> +			cabc_backlight_device_unregister(connector);
> +		else
> +			intel_backlight_device_unregister(connector);
> +	}
>   }
> diff --git a/include/video/mipi_display.h b/include/video/mipi_display.h
> index ddcc8ca..5b8eeec 100644
> --- a/include/video/mipi_display.h
> +++ b/include/video/mipi_display.h
> @@ -117,6 +117,14 @@ enum {
>   	MIPI_DCS_GET_SCANLINE		= 0x45,
>   	MIPI_DCS_READ_DDB_START		= 0xA1,
>   	MIPI_DCS_READ_DDB_CONTINUE	= 0xA8,
> +	MIPI_DCS_CABC_LEVEL_RD          = 0x52,
> +	MIPI_DCS_CABC_MIN_BRIGHTNESS_RD = 0x5F,
> +	MIPI_DCS_CABC_CONTROL_RD        = 0x56,
> +	MIPI_DCS_CABC_CONTROL_BRIGHT_RD = 0x54,
> +	MIPI_DCS_CABC_LEVEL_WR          = 0x51,
> +	MIPI_DCS_CABC_MIN_BRIGHTNESS_WR = 0x5E,
> +	MIPI_DCS_CABC_CONTROL_WR        = 0x55,
> +	MIPI_DCS_CABC_CONTROL_BRIGHT_WR = 0x53,
>   };
>   
>   /* MIPI DCS pixel formats */
On 7/30/2015 4:18 PM, Singh, Gaurav K wrote:
>
>
> On 7/24/2015 5:54 PM, Deepak M wrote:
>> In CABC (Content Adaptive Brightness Control) content grey level
>> scale can be increased while simultaneously decreasing
>> brightness of the backlight to achieve same perceived brightness.
>>
>> The CABC is not standardized and panel vendors are free to follow
>> their implementation. The CABC implementaion here assumes that the
>> panels use standard SW register for control.
>>
>> In this design there will be no PWM signal from the SoC and DCS
>> commands are sent to enable and control the backlight brightness.
>>
>> v2:
>> - Created a new backlight driver for cabc, which will be registered
>>    only when it cabc is supported by panel.
>>    (Addressed comment from Daniel Vetter)
>>
>> Signed-off-by: Deepak M <m.deepak@intel.com>
>> ---
>>   drivers/gpu/drm/i915/Makefile         |    1 +
>>   drivers/gpu/drm/i915/intel_drv.h      |    3 +-
>>   drivers/gpu/drm/i915/intel_dsi.c      |   13 ++
>>   drivers/gpu/drm/i915/intel_dsi_cabc.c |  349 
>> +++++++++++++++++++++++++++++++++
>>   drivers/gpu/drm/i915/intel_dsi_cabc.h |   45 +++++
>>   drivers/gpu/drm/i915/intel_panel.c    |   22 ++-
>>   include/video/mipi_display.h          |    8 +
>>   7 files changed, 436 insertions(+), 5 deletions(-)
>>   create mode 100644 drivers/gpu/drm/i915/intel_dsi_cabc.c
>>   create mode 100644 drivers/gpu/drm/i915/intel_dsi_cabc.h
>>
>> diff --git a/drivers/gpu/drm/i915/Makefile 
>> b/drivers/gpu/drm/i915/Makefile
>> index de21965..a73953c 100644
>> --- a/drivers/gpu/drm/i915/Makefile
>> +++ b/drivers/gpu/drm/i915/Makefile
>> @@ -75,6 +75,7 @@ i915-y += dvo_ch7017.o \
>>         intel_dp_mst.o \
>>         intel_dsi.o \
>>         intel_dsi_pll.o \
>> +      intel_dsi_cabc.o \
>>         intel_dsi_panel_vbt.o \
>>         intel_dvo.o \
>>         intel_hdmi.o \
>> diff --git a/drivers/gpu/drm/i915/intel_drv.h 
>> b/drivers/gpu/drm/i915/intel_drv.h
>> index 3f0a890..9f806dd5 100644
>> --- a/drivers/gpu/drm/i915/intel_drv.h
>> +++ b/drivers/gpu/drm/i915/intel_drv.h
>> @@ -1319,7 +1319,8 @@ extern struct drm_display_mode 
>> *intel_find_panel_downclock(
>>                   struct drm_connector *connector);
>>   void intel_backlight_register(struct drm_device *dev);
>>   void intel_backlight_unregister(struct drm_device *dev);
>> -
>> +extern int cabc_backlight_device_register(struct intel_connector 
>> *connector);
>> +extern void cabc_backlight_device_unregister(struct intel_connector 
>> *connector);
>>     /* intel_psr.c */
>>   void intel_psr_enable(struct intel_dp *intel_dp);
>> diff --git a/drivers/gpu/drm/i915/intel_dsi.c 
>> b/drivers/gpu/drm/i915/intel_dsi.c
>> index 98998e9..8f006f2 100644
>> --- a/drivers/gpu/drm/i915/intel_dsi.c
>> +++ b/drivers/gpu/drm/i915/intel_dsi.c
>> @@ -34,6 +34,7 @@
>>   #include "i915_drv.h"
>>   #include "intel_drv.h"
>>   #include "intel_dsi.h"
>> +#include "intel_dsi_cabc.h"
>>     static const struct {
>>       u16 panel_id;
>> @@ -376,6 +377,7 @@ static void intel_dsi_enable(struct intel_encoder 
>> *encoder)
>>       struct drm_device *dev = encoder->base.dev;
>>       struct drm_i915_private *dev_priv = dev->dev_private;
>>       struct intel_dsi *intel_dsi = enc_to_intel_dsi(&encoder->base);
>> +    struct intel_connector *connector = intel_dsi->attached_connector;
>>       enum port port;
>>         DRM_DEBUG_KMS("\n");
>> @@ -396,6 +398,9 @@ static void intel_dsi_enable(struct intel_encoder 
>> *encoder)
>>             intel_dsi_port_enable(encoder);
>>       }
>> +
>> +    if (dev_priv->vbt.dsi.config->cabc_supported)
>> +        cabc_enable_backlight(connector);
>>   }
>>     static void intel_dsi_pre_enable(struct intel_encoder *encoder)
>> @@ -469,11 +474,15 @@ static void intel_dsi_disable(struct 
>> intel_encoder *encoder)
>>       struct drm_device *dev = encoder->base.dev;
>>       struct drm_i915_private *dev_priv = dev->dev_private;
>>       struct intel_dsi *intel_dsi = enc_to_intel_dsi(&encoder->base);
>> +    struct intel_connector *connector = intel_dsi->attached_connector;
>>       enum port port;
>>       u32 temp;
>>         DRM_DEBUG_KMS("\n");
>>   +    if (dev_priv->vbt.dsi.config->cabc_supported)
>> +        cabc_disable_backlight(connector);
>> +
>>       if (is_vid_mode(intel_dsi)) {
>>           for_each_dsi_port(port, intel_dsi->ports)
>>               wait_for_dsi_fifo_empty(intel_dsi, port);
>> @@ -1099,6 +1108,10 @@ void intel_dsi_init(struct drm_device *dev)
>>         intel_panel_init(&intel_connector->panel, fixed_mode, NULL);
>>   +    if (dev_priv->vbt.dsi.config->cabc_supported)
>> +        cabc_setup_backlight(connector,
>> +            intel_encoder->crtc_mask ==
>> +                (1 << PIPE_A) ? PIPE_A : PIPE_B);
>>       return;
>>     err:
>> diff --git a/drivers/gpu/drm/i915/intel_dsi_cabc.c 
>> b/drivers/gpu/drm/i915/intel_dsi_cabc.c
>> new file mode 100644
>> index 0000000..2a78326
>> --- /dev/null
>> +++ b/drivers/gpu/drm/i915/intel_dsi_cabc.c
>> @@ -0,0 +1,349 @@
>> +/*
>> + * Copyright © 2006-2010 Intel Corporation
>> + *
>> + * Permission is hereby granted, free of charge, to any person 
>> obtaining a
>> + * copy of this software and associated documentation files (the 
>> "Software"),
>> + * to deal in the Software without restriction, including without 
>> limitation
>> + * the rights to use, copy, modify, merge, publish, distribute, 
>> sublicense,
>> + * and/or sell copies of the Software, and to permit persons to whom 
>> the
>> + * Software is furnished to do so, subject to the following conditions:
>> + *
>> + * The above copyright notice and this permission notice (including 
>> the next
>> + * paragraph) shall be included in all copies or substantial 
>> portions of the
>> + * Software.
>> + *
>> + * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, 
>> EXPRESS OR
>> + * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF 
>> MERCHANTABILITY,
>> + * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO 
>> EVENT SHALL
>> + * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES 
>> OR OTHER
>> + * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, 
>> ARISING
>> + * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
>> + * DEALINGS IN THE SOFTWARE.
>> + *
>> + */
>> +
>> +#include <linux/kernel.h>
>> +#include <linux/moduleparam.h>
>> +#include "intel_drv.h"
>> +#include "intel_dsi.h"
>> +#include "i915_drv.h"
>> +#include "intel_dsi_cabc.h"
>> +#include <video/mipi_display.h>
>> +#include <drm/drm_mipi_dsi.h>
>> +
>> +int cabc_setup_backlight(struct intel_connector *connector,
>> +        enum pipe unused)
>> +{
>> +    struct drm_device *dev = connector->base.dev;
>> +    struct intel_dsi *intel_dsi = NULL;
>> +    struct drm_crtc *crtc = NULL;
>> +    struct intel_encoder *encoder = NULL;
>> +    struct intel_panel *panel = &connector->panel;
>> +    struct mipi_dsi_device *dsi_device;
>> +    u8 level;
>> +
>> +    list_for_each_entry(crtc, &dev->mode_config.crtc_list, head) {
>> +        for_each_encoder_on_crtc(dev, crtc, encoder) {
>> +            if (encoder->type == INTEL_OUTPUT_DSI)
>> +                intel_dsi = enc_to_intel_dsi(&encoder->base);
>> +        }
>> +    }
>> +    dsi_device = intel_dsi->dsi_hosts[0]->device;
> This will work only for MIPI Port A not for MIPI Port C. Use 
> for_each_dsi_port macro and intel_dsi->dsi_hosts[port] to correctly 
> reach to mipi_dsi_device for both ports. If it is dual link, break 
> after the completion of the first iteration.
>> +    panel->backlight.max = CABC_MAX_VALUE;
>> +    panel->backlight.level = CABC_MAX_VALUE;
>> +    level = CABC_MAX_VALUE;
>> +    panel->backlight.enabled = true;
>> +    return 0;
>> +}
>> +
>> +u32 cabc_get_backlight(struct intel_connector *connector)
>> +{
>> +    struct drm_device *dev = connector->base.dev;
>> +    struct intel_dsi *intel_dsi = NULL;
>> +    struct drm_crtc *crtc = NULL;
>> +    struct intel_encoder *encoder = NULL;
>> +    struct mipi_dsi_device *dsi_device;
>> +    struct intel_panel *panel = &connector->panel;
>> +    u8 data[2] = {0};
>> +    enum port port = PORT_A;
> will fail for single link MIPI Port C.
>> +    u32 ret;
>> +
>> +    list_for_each_entry(crtc, &dev->mode_config.crtc_list, head) {
>> +        for_each_encoder_on_crtc(dev, crtc, encoder) {
>> +            if (encoder->type == INTEL_OUTPUT_DSI)
>> +                intel_dsi = enc_to_intel_dsi(&encoder->base);
>> +        }
>> +    }
>> +    if (intel_dsi->dual_link) {
> Put the below or required logic into static inline function returning 
> enum port .
>> +        if (intel_dsi->dl_cabc_port == CABC_PORT_A ||
>> +                intel_dsi->dl_cabc_port == CABC_PORT_A_AND_C)
>> +            port = PORT_A;
>> +        else if (intel_dsi->dl_cabc_port == CABC_PORT_C)
>> +            port = PORT_C;
>> +    }
> Use for_each_dsi_port macro here . call the  inline function within 
> for_each_dsi_port macro to get the required enum port for dual link.
>> +
>> +    dsi_device = intel_dsi->dsi_hosts[port]->device;
>> +    mipi_dsi_dcs_read(dsi_device, MIPI_DCS_CABC_LEVEL_RD, data, 2);
>> +
>> +    ret = (data[1] * panel->backlight.max) / 255;
>> +    return ret;
>> +}
>> +
>> +void cabc_set_backlight(struct intel_connector *connector, u32 level)
>> +{
>> +    struct drm_device *dev = connector->base.dev;
>> +    struct intel_dsi *intel_dsi = NULL;
>> +    struct drm_crtc *crtc = NULL;
>> +    struct intel_encoder *encoder = NULL;
>> +    struct mipi_dsi_device *dsi_device;
>> +    u8 data[2] = {0};
>> +    enum port port = PORT_A;
>> +    struct intel_panel *panel = &connector->panel;
>> +    u8 count = 1;
>> +    u32 hw_level;
>> +
>> +    list_for_each_entry(crtc, &dev->mode_config.crtc_list, head) {
>> +        for_each_encoder_on_crtc(dev, crtc, encoder) {
>> +            if (encoder->type == INTEL_OUTPUT_DSI)
>> +                intel_dsi = enc_to_intel_dsi(&encoder->base);
>> +        }
>> +    }
>> +
>> +    if (intel_dsi->dual_link) {
> Put the below logic into static inline function returning enum port .
>> +        if (intel_dsi->dl_cabc_port == CABC_PORT_A)
>> +            port = PORT_A;
>> +        else if (intel_dsi->dl_cabc_port == CABC_PORT_C)
>> +            port = PORT_C;
>> +        else if (intel_dsi->dl_cabc_port == CABC_PORT_A_AND_C)
>> +            port = PORT_A;
>> +    }
>> +
> Below part not required. use for_each_dsi_port macro.
>> +    if (intel_dsi->dual_link && intel_dsi->dl_cabc_port ==
>> +            CABC_PORT_A_AND_C)
>> +        count = 2;
>> +
>> +
>> +    hw_level = level % (panel->backlight.max + 1);
>> +    hw_level = (hw_level * 255) / panel->backlight.max;
>> +    panel->backlight.level = hw_level;
>> +
> Use for_each_dsi_port macro as explained above.
>> +    do {
>> +        dsi_device = intel_dsi->dsi_hosts[port]->device;
>> +        data[1] = hw_level;
>> +        data[0] = MIPI_DCS_CABC_LEVEL_WR;
>> +        mipi_dsi_dcs_write_buffer(dsi_device, data, 2);
>> +        if (count == 2)
>> +            port = PORT_C;
>> +    } while (--count > 0);
>> +}
>> +
>> +void cabc_enable_backlight(struct intel_connector *connector)
>> +{
>> +    struct drm_device *dev = connector->base.dev;
>> +    struct intel_dsi *intel_dsi = NULL;
>> +    struct drm_crtc *crtc = NULL;
>> +    struct intel_encoder *encoder = NULL;
>> +    struct intel_panel *panel = &connector->panel;
>> +    struct mipi_dsi_device *dsi_device;
>> +    enum port port = PORT_A;
> Will fail for single link Port C
>> +    u8 data[2] = {0};
>> +    u8 count = 1;
>> +
>> +    list_for_each_entry(crtc, &dev->mode_config.crtc_list, head) {
>> +        for_each_encoder_on_crtc(dev, crtc, encoder) {
>> +            if (encoder->type == INTEL_OUTPUT_DSI)
>> +                intel_dsi = enc_to_intel_dsi(&encoder->base);
>> +        }
>> +    }
>> +
>> +    if (intel_dsi->dual_link) {
> Same comment .Put the below logic into static inline function 
> returning enum port .
>> +        if (intel_dsi->dl_cabc_port == CABC_PORT_A)
>> +            port = PORT_A;
>> +        else if (intel_dsi->dl_cabc_port == CABC_PORT_C)
>> +            port = PORT_C;
> Also below condition need not be taken into the inline function. Since 
> it is dual link and with other conditions are met, then 
> CABC_PORT_A_AND_C will be automatically taken care for both ports by 
> the for_each_dsi_port macro.
> Within for_each_dsi_port, just check for intel_dsi->dl_cabc_port != 
> CABC_PORT_A_AND_C, if yes call the inline function to get the port no 
> and if no, all other conditions will be taken care for both ports by 
> for_each_dsi_port.
> Before the end of for_each_dsi_port ,you may require to check the 
> intel_dsi->dl_cabc_port != CABC_PORT_A_AND_C , so that you can return 
> from the macro.
>> +        else if (intel_dsi->dl_cabc_port == CABC_PORT_A_AND_C)
>> +            port = PORT_A;
>> +    }
>> +
>> +    if (intel_dsi->dual_link && intel_dsi->dl_cabc_port ==
>> +            CABC_PORT_A_AND_C)
>> +        count = 2;
>> +
>> +    do {
> same comment as above. Use for_each_dsi_port
>> +        dsi_device = intel_dsi->dsi_hosts[port]->device;
>> +
>> +
>> +        data[0] = MIPI_DCS_CABC_CONTROL_BRIGHT_WR;
>> +        data[1] = CABC_BACKLIGHT | CABC_DIMMING_DISPLAY | CABC_BCTRL;
>> +        mipi_dsi_dcs_write_buffer(dsi_device, data, 2);
>> +        data[0] = MIPI_DCS_CABC_CONTROL_WR;
>> +        data[1] = CABC_VIDEO_MODE;
>> +        mipi_dsi_dcs_write_buffer(dsi_device, data, 2);
>> +
>> +        if (count == 2)
>> +            port = PORT_C;
>> +    } while (--count > 0);
>> +
>> +    cabc_set_backlight(connector, panel->backlight.level);
>> +}
>> +
>> +void cabc_disable_backlight(struct intel_connector *connector)
>> +{
>> +    struct drm_device *dev = connector->base.dev;
>> +    struct intel_dsi *intel_dsi = NULL;
>> +    struct drm_crtc *crtc = NULL;
>> +    struct intel_encoder *encoder = NULL;
>> +    struct mipi_dsi_device *dsi_device;
>> +    enum port port = PORT_A;
> Will fail for single link Port C
>> +    u8 data[2] = {0};
>> +    u8 count = 1;
>> +
>> +    list_for_each_entry(crtc, &dev->mode_config.crtc_list, head) {
>> +        for_each_encoder_on_crtc(dev, crtc, encoder) {
>> +            if (encoder->type == INTEL_OUTPUT_DSI)
>> +                intel_dsi = enc_to_intel_dsi(&encoder->base);
>> +        }
>> +    }
>> +
>> +    if (intel_dsi->dual_link) {
> Same comment as above. Use static inline function for this.
>> +        if (intel_dsi->dl_cabc_port == CABC_PORT_A)
>> +            port = PORT_A;
>> +        else if (intel_dsi->dl_cabc_port == CABC_PORT_C)
>> +            port = PORT_C;
>> +        else if (intel_dsi->dl_cabc_port == CABC_PORT_A_AND_C)
>> +            port = PORT_A;
>> +    }
>> +
>> +    if (intel_dsi->dual_link && intel_dsi->dl_cabc_port ==
>> +            CABC_PORT_A_AND_C)
>> +        count = 2;
>> +
>> +    do {
> Use for_each_dsi_port macro
>> +        dsi_device = intel_dsi->dsi_hosts[port]->device;
>> +
>> +        cabc_set_backlight(connector, 0);
>> +        data[1] = CABC_OFF;
>> +        data[0] = MIPI_DCS_CABC_CONTROL_WR;
>> +        mipi_dsi_dcs_write_buffer(dsi_device, data, 2);
>> +        data[0] = MIPI_DCS_CABC_CONTROL_BRIGHT_WR;
>> +        mipi_dsi_dcs_write_buffer(dsi_device, data, 2);
>> +
>> +        if (count == 2)
>> +            port = PORT_C;
>> +    } while (--count > 0);
>> +}
>> +
>> +static int cabc_backlight_device_update_status(struct 
>> backlight_device *bd)
>> +{
>> +    struct intel_connector *connector = bl_get_data(bd);
>> +    struct intel_panel *panel = &connector->panel;
>> +    struct drm_device *dev = connector->base.dev;
>> +
>> +    drm_modeset_lock(&dev->mode_config.connection_mutex, NULL);
>> +    DRM_DEBUG_KMS("updating intel_backlight, brightness=%d/%d\n",
>> +            bd->props.brightness, bd->props.max_brightness);
>> +    cabc_set_backlight(connector, bd->props.brightness);
>> +
>> +    /*
>> +     * Allow flipping bl_power as a sub-state of enabled. Sadly the
>> +     * backlight class device does not make it easy to to differentiate
>> +     * between callbacks for brightness and bl_power, so our 
>> backlight_power
>> +     * callback needs to take this into account.
>> +     */
>> +    if (panel->backlight.enabled) {
>> +        if (panel->backlight_power) {
>> +            bool enable = bd->props.power == FB_BLANK_UNBLANK &&
>> +                bd->props.brightness != 0;
>> +            panel->backlight_power(connector, enable);
>> +        }
>> +    } else {
>> +        bd->props.power = FB_BLANK_POWERDOWN;
>> +    }
>> +
>> + drm_modeset_unlock(&dev->mode_config.connection_mutex);
>> +    return 0;
>> +}
>> +
>> +static int cabc_backlight_device_get_brightness(struct 
>> backlight_device *bd)
>> +{
>> +    struct intel_connector *connector = bl_get_data(bd);
>> +    struct drm_device *dev = connector->base.dev;
>> +    struct drm_i915_private *dev_priv = dev->dev_private;
>> +    int ret;
>> +
>> +    intel_runtime_pm_get(dev_priv);
>> +    drm_modeset_lock(&dev->mode_config.connection_mutex, NULL);
>> +
>> +    ret = cabc_get_backlight(connector);
>> +
>> + drm_modeset_unlock(&dev->mode_config.connection_mutex);
>> +    intel_runtime_pm_put(dev_priv);
>> +
>> +    return ret;
>> +}
>> +
>> +static const struct backlight_ops cabc_backlight_device_ops = {
>> +    .update_status = cabc_backlight_device_update_status,
>> +    .get_brightness = cabc_backlight_device_get_brightness,
>> +};
>> +
>> +int cabc_backlight_device_register(struct intel_connector *connector)
>> +{
>> +    struct intel_panel *panel = &connector->panel;
>> +    struct backlight_properties props;
>> +
>> +    if (WARN_ON(panel->backlight.device))
>> +        return -ENODEV;
>> +
>> +    if (!panel->backlight.present)
>> +        return 0;
>> +
>> +    WARN_ON(panel->backlight.max == 0);
>> +
>> +    memset(&props, 0, sizeof(props));
>> +    props.type = BACKLIGHT_FIRMWARE;
>> +
>> +    /*
>> +     * Note: Everything should work even if the backlight device max
>> +     * presented to the userspace is arbitrarily chosen.
>> +     */
>> +    props.max_brightness = panel->backlight.max;
>> +    props.brightness = props.max_brightness;
>> +
>> +    if (panel->backlight.enabled)
>> +        props.power = FB_BLANK_UNBLANK;
>> +    else
>> +        props.power = FB_BLANK_POWERDOWN;
>> +
>> +    /*
>> +     * Note: using the same name independent of the connector prevents
>> +     * registration of multiple backlight devices in the driver.
>> +     */
>> +    panel->backlight.device =
>> +        backlight_device_register("intel_backlight",
>> +                connector->base.kdev,
>> +                connector,
>> +                &cabc_backlight_device_ops, &props);
>> +
>> +    if (IS_ERR(panel->backlight.device)) {
>> +        DRM_ERROR("Failed to register backlight: %ld\n",
>> +                PTR_ERR(panel->backlight.device));
>> +        panel->backlight.device = NULL;
>> +        return -ENODEV;
>> +    }
>> +
>> +    DRM_DEBUG_KMS("Connector %s backlight sysfs interface 
>> registered\n",
>> +            connector->base.name);
>> +
>> +    return 0;
>> +}
>> +
>> +void cabc_backlight_device_unregister(struct intel_connector 
>> *connector)
>> +{
>> +    struct intel_panel *panel = &connector->panel;
>> +
>> +    if (panel->backlight.device) {
>> + backlight_device_unregister(panel->backlight.device);
>> +        panel->backlight.device = NULL;
>> +    }
>> +}
>> diff --git a/drivers/gpu/drm/i915/intel_dsi_cabc.h 
>> b/drivers/gpu/drm/i915/intel_dsi_cabc.h
>> new file mode 100644
>> index 0000000..5d134f5
>> --- /dev/null
>> +++ b/drivers/gpu/drm/i915/intel_dsi_cabc.h
>> @@ -0,0 +1,45 @@
>> +/*
>> + * Copyright © 2013 Intel Corporation
>> + *
>> + * Permission is hereby granted, free of charge, to any person 
>> obtaining a
>> + * copy of this software and associated documentation files (the 
>> "Software"),
>> + * to deal in the Software without restriction, including without 
>> limitation
>> + * the rights to use, copy, modify, merge, publish, distribute, 
>> sublicense,
>> + * and/or sell copies of the Software, and to permit persons to whom 
>> the
>> + * Software is furnished to do so, subject to the following conditions:
>> + *
>> + * The above copyright notice and this permission notice (including 
>> the next
>> + * paragraph) shall be included in all copies or substantial 
>> portions of the
>> + * Software.
>> + *
>> + * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, 
>> EXPRESS OR
>> + * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF 
>> MERCHANTABILITY,
>> + * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO 
>> EVENT SHALL
>> + * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES 
>> OR OTHER
>> + * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, 
>> ARISING
>> + * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
>> + * DEALINGS IN THE SOFTWARE.
>> + *
>> + */
>> +
>> +extern int cabc_backlight_device_register(struct intel_connector 
>> *connector);
>> +extern void cabc_backlight_device_unregister(struct intel_connector 
>> *connector);
>> +void cabc_set_backlight(struct intel_connector *connector, u32 level);
>> +u32 cabc_get_backlight(struct intel_connector *connector);
>> +void cabc_enable_backlight(struct intel_connector *connector);
>> +void cabc_disable_backlight(struct intel_connector *connector);
>> +int cabc_setup_backlight(struct intel_connector *connector, enum 
>> pipe unused);
>> +
>> +#define CABC_OFF                       (0 << 0)
>> +#define CABC_USER_INTERFACE_IMAGE      (1 << 0)
>> +#define CABC_STILL_PICTURE             (2 << 0)
>> +#define CABC_VIDEO_MODE                        (3 << 0)
>> +
>> +#define CABC_BACKLIGHT                 (1 << 2)
>> +#define CABC_DIMMING_DISPLAY           (1 << 3)
>> +#define CABC_BCTRL                     (1 << 5)
>> +
>> +#define CABC_PORT_A                    0x00
>> +#define CABC_PORT_C                    0x01
>> +#define CABC_PORT_A_AND_C              0x02
>> +#define CABC_MAX_VALUE               0xff
>> diff --git a/drivers/gpu/drm/i915/intel_panel.c 
>> b/drivers/gpu/drm/i915/intel_panel.c
>> index 55aad23..c73449b 100644
>> --- a/drivers/gpu/drm/i915/intel_panel.c
>> +++ b/drivers/gpu/drm/i915/intel_panel.c
>> @@ -1502,15 +1502,29 @@ void intel_panel_fini(struct intel_panel *panel)
>>   void intel_backlight_register(struct drm_device *dev)
>>   {
>>       struct intel_connector *connector;
>> +    struct drm_i915_private *dev_priv = dev->dev_private;
>>   -    list_for_each_entry(connector, 
>> &dev->mode_config.connector_list, base.head)
>> -        intel_backlight_device_register(connector);
>> +    list_for_each_entry(connector, &dev->mode_config.connector_list,
>> +                    base.head) {
>> +        if (connector->encoder->type == INTEL_OUTPUT_DSI &&
>> +            dev_priv->vbt.dsi.config->cabc_supported)
>> +            cabc_backlight_device_register(connector);
>> +        else
>> +            intel_backlight_device_register(connector);
>> +    }
>>   }
>>     void intel_backlight_unregister(struct drm_device *dev)
>>   {
>>       struct intel_connector *connector;
>> +    struct drm_i915_private *dev_priv = dev->dev_private;
>>   -    list_for_each_entry(connector, 
>> &dev->mode_config.connector_list, base.head)
>> -        intel_backlight_device_unregister(connector);
>> +    list_for_each_entry(connector, &dev->mode_config.connector_list,
>> +                    base.head) {
>> +        if (connector->encoder->type == INTEL_OUTPUT_DSI &&
>> +            dev_priv->vbt.dsi.config->cabc_supported)
>> +            cabc_backlight_device_unregister(connector);
>> +        else
>> +            intel_backlight_device_unregister(connector);
>> +    }
>>   }
>> diff --git a/include/video/mipi_display.h b/include/video/mipi_display.h
>> index ddcc8ca..5b8eeec 100644
>> --- a/include/video/mipi_display.h
>> +++ b/include/video/mipi_display.h
>> @@ -117,6 +117,14 @@ enum {
>>       MIPI_DCS_GET_SCANLINE        = 0x45,
>>       MIPI_DCS_READ_DDB_START        = 0xA1,
>>       MIPI_DCS_READ_DDB_CONTINUE    = 0xA8,
Please add them in increment order. Also, in HLD it is mentioned that 
offset for MIPI_DCS_CABC_LEVEL_RD is 0x51. Correct either of them 
accordingly.
>> +    MIPI_DCS_CABC_LEVEL_RD          = 0x52,
>> +    MIPI_DCS_CABC_MIN_BRIGHTNESS_RD = 0x5F,
>> +    MIPI_DCS_CABC_CONTROL_RD        = 0x56,
>> +    MIPI_DCS_CABC_CONTROL_BRIGHT_RD = 0x54,
>> +    MIPI_DCS_CABC_LEVEL_WR          = 0x51,
>> +    MIPI_DCS_CABC_MIN_BRIGHTNESS_WR = 0x5E,
>> +    MIPI_DCS_CABC_CONTROL_WR        = 0x55,
>> +    MIPI_DCS_CABC_CONTROL_BRIGHT_WR = 0x53,
>>   };
>>     /* MIPI DCS pixel formats */
>