[1/4] drm: Add helper for DP++ adaptors

Submitted by Ville Syrjälä on Feb. 23, 2016, 4:46 p.m.

Details

Message ID 1456245988-19442-2-git-send-email-ville.syrjala@linux.intel.com
State New
Headers show
Series "drm: DP++ adaptor support" ( rev: 1 ) in DRI devel

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Commit Message

Ville Syrjälä Feb. 23, 2016, 4:46 p.m.
From: Ville Syrjälä <ville.syrjala@linux.intel.com>

Add a helper which aids in he identification of DP dual mode (aka. DP++)
adaptors. There are several types of adaptors specified:
type 1 DVI, type 1 HDMI, type 2 DVI, type 2 HDMI

Type 1 adaptors have a max TMDS clock limit of 165MHz, type 2 adaptors
may go as high as 300MHz and they provide a register informing the
source device what the actual limit is. Supposedly also type 1 adaptors
may optionally implement this register. This TMDS clock limit is the
main reason why we need to identify these adaptors.

Type 1 adaptors provide access to their internal registers and the sink
DDC bus through I2C. Type 2 adaptors provide this access both via I2C
and I2C-over-AUX. A type 2 source device may choose to implement either
or both of these methods. If a source device implements only the
I2C-over-AUX method, then the driver will obviously need specific
support for such adaptors since the port is driven like an HDMI port,
but DDC communication happes over the AUX channel.

This helper should be enough to identify the adaptor type (some
type 1 DVI adaptors may be a slight exception) and the maximum TMDS
clock limit. Another feature that may be available is control over
the TMDS output buffers on the adaptor, possibly allowing for some
power saving when the TMDS link is down.

Other user controllable features that may be available in the adaptors
are downstream i2c bus speed control when using i2c-over-aux, and
some control over the CEC pin. I chose not to provide any helper
functions for those since I have no use for them in i915 at this time.
The rest of the registers in the adaptor are mostly just information,
eg. IEEE OUI, hardware and firmware revision, etc.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
---
 drivers/gpu/drm/Makefile                  |   2 +-
 drivers/gpu/drm/drm_dp_dual_mode_helper.c | 328 ++++++++++++++++++++++++++++++
 include/drm/drm_dp_dual_mode_helper.h     |  80 ++++++++
 3 files changed, 409 insertions(+), 1 deletion(-)
 create mode 100644 drivers/gpu/drm/drm_dp_dual_mode_helper.c
 create mode 100644 include/drm/drm_dp_dual_mode_helper.h

Patch hide | download patch | download mbox

diff --git a/drivers/gpu/drm/Makefile b/drivers/gpu/drm/Makefile
index 6eb94fc561dc..22228ef50f36 100644
--- a/drivers/gpu/drm/Makefile
+++ b/drivers/gpu/drm/Makefile
@@ -23,7 +23,7 @@  drm-$(CONFIG_AGP) += drm_agpsupport.o
 
 drm_kms_helper-y := drm_crtc_helper.o drm_dp_helper.o drm_probe_helper.o \
 		drm_plane_helper.o drm_dp_mst_topology.o drm_atomic_helper.o \
-		drm_kms_helper_common.o
+		drm_kms_helper_common.o drm_dp_dual_mode_helper.o
 
 drm_kms_helper-$(CONFIG_DRM_LOAD_EDID_FIRMWARE) += drm_edid_load.o
 drm_kms_helper-$(CONFIG_DRM_FBDEV_EMULATION) += drm_fb_helper.o
diff --git a/drivers/gpu/drm/drm_dp_dual_mode_helper.c b/drivers/gpu/drm/drm_dp_dual_mode_helper.c
new file mode 100644
index 000000000000..bfe511c09568
--- /dev/null
+++ b/drivers/gpu/drm/drm_dp_dual_mode_helper.c
@@ -0,0 +1,328 @@ 
+/*
+ * Copyright © 2016 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 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 COPYRIGHT HOLDER(S) OR AUTHOR(S) 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/errno.h>
+#include <linux/export.h>
+#include <linux/i2c.h>
+#include <linux/slab.h>
+#include <linux/string.h>
+#include <drm/drm_dp_dual_mode_helper.h>
+#include <drm/drmP.h>
+
+/**
+ * DOC: DP dual mode (aka. DP++) adaptor helpers
+ *
+ * Helper functions to deal with DP dual mode adaptors.
+ *
+ * Type 1:
+ * Adaptor registers (if any) and the sink DDC bus may be accessed via I2C.
+ *
+ * Type 2:
+ * Adaptor registers and sink DDC bus can be accessed either via I2C or
+ * I2C-over-AUX. Source devices may choose to implement either one or
+ * both of these access methods.
+ */
+
+#define DP_DUAL_MODE_SLAVE_ADDRESS 0x40
+
+/**
+ * drm_dp_dual_mode_read - Read from the DP dual mode adaptor register(s)
+ * adapter: I2C adapter for the DDC bus
+ * offset: register offset
+ * buffer: buffer for return data
+ * size: sizo of the buffer
+ *
+ * Reads @size bytes from the DP dual mode adaptor registers
+ * starting at @offset.
+ *
+ * Returns:
+ * 0 on success, negative error code on failure
+ */
+ssize_t drm_dp_dual_mode_read(struct i2c_adapter *adapter,
+			      u8 offset, void *buffer, size_t size)
+{
+	struct i2c_msg msgs[] = {
+		{
+			.addr = DP_DUAL_MODE_SLAVE_ADDRESS,
+			.flags = 0,
+			.len = 1,
+			.buf = &offset,
+		},
+		{
+			.addr = DP_DUAL_MODE_SLAVE_ADDRESS,
+			.flags = I2C_M_RD,
+			.len = size,
+			.buf = buffer,
+		},
+	};
+	int ret;
+
+	ret = i2c_transfer(adapter, msgs, ARRAY_SIZE(msgs));
+	if (ret < 0)
+		return ret;
+	if (ret != ARRAY_SIZE(msgs))
+		return -EPROTO;
+
+	return 0;
+}
+
+/**
+ * drm_dp_dual_mode_write - Write to the DP dual mode adaptor register(s)
+ * adapter: I2C adapter for the DDC bus
+ * offset: register offset
+ * buffer: buffer for write data
+ * size: sizo of the buffer
+ *
+ * Writes @size bytes to the DP dual mode adaptor registers
+ * starting at @offset.
+ *
+ * Returns:
+ * 0 on success, negative error code on failure
+ */
+ssize_t drm_dp_dual_mode_write(struct i2c_adapter *adapter,
+			       u8 offset, const void *buffer, size_t size)
+{
+	struct i2c_msg msg = {
+		.addr = DP_DUAL_MODE_SLAVE_ADDRESS,
+		.flags = 0,
+		.len = 1 + size,
+		.buf = NULL,
+	};
+	void *data;
+	int ret;
+
+	data = kmalloc(msg.len, GFP_TEMPORARY);
+	if (!data)
+		return -ENOMEM;
+
+	msg.buf = data;
+
+	memcpy(data, &offset, 1);
+	memcpy(data + 1, buffer, size);
+
+	ret = i2c_transfer(adapter, &msg, 1);
+
+	kfree(data);
+
+	if (ret < 0)
+		return ret;
+	if (ret != 1)
+		return -EPROTO;
+
+	return 0;
+}
+EXPORT_SYMBOL(drm_dp_dual_mode_write);
+
+static bool is_hdmi_adaptor(const char hdmi_id[DP_DUAL_MODE_HDMI_ID_LEN])
+{
+	static const char dp_dual_mode_hdmi_id[DP_DUAL_MODE_HDMI_ID_LEN] =
+		"DP-HDMI ADAPTOR\x04";
+
+	return memcmp(hdmi_id, dp_dual_mode_hdmi_id,
+		      sizeof(dp_dual_mode_hdmi_id)) == 0;
+}
+
+/**
+ * drm_dp_dual_mode_detect - Identyfy the DP dual mode adaptor
+ * adapter: I2C adapter for the DDC bus
+ *
+ * Attempt to identify the type of the DP dual mode adaptor used.
+ *
+ * Note that when the answer is @DRM_DP_DUAL_MODE_NONE it's not
+ * certain whether we're dealing with a native HDMI port or
+ * a type 1 DVI dual mode adaptor. The driver will have to use
+ * some other hardware/driver specific mechanism to make that
+ * distinction.
+ *
+ * Returns:
+ * The type of the DP dual mode adaptor used
+ */
+enum drm_dp_dual_mode_type drm_dp_dual_mode_detect(struct i2c_adapter *adapter)
+{
+	char hdmi_id[DP_DUAL_MODE_HDMI_ID_LEN] = {};
+	uint8_t adaptor_id = 0x00;
+	ssize_t ret;
+
+	/*
+	 * Let's see if the adaptor is there the by reading the
+	 * HDMI ID registers.
+	 *
+	 * Note that type 1 DVI adaptors are not required to implemnt
+	 * any registers, and that presents a problem for detection.
+	 * If the i2c transfer is nacked, we may or may not be dealing
+	 * with a type 1 DVI adaptor. Some other mechanism of detecting
+	 * the presence of the adaptor is required. One way would be
+	 * to check the state of the CONFIG1 pin, Another method would
+	 * simply require the driver to know whether the port is a DP++
+	 * port or a native HDMI port. Both of these methods are entirely
+	 * hardware/driver specific so we can't deal with them here.
+	 */
+	ret = drm_dp_dual_mode_read(adapter, DP_DUAL_MODE_HDMI_ID,
+				    hdmi_id, sizeof(hdmi_id));
+	if (ret)
+		return DRM_DP_DUAL_MODE_NONE;
+
+	/*
+	 * Sigh. Some (maybe all?) type 1 adaptors are broken and ack
+	 * the offset but ignore it, and instead they just always return
+	 * data from the start of the HDMI ID buffer. So for a broken
+	 * type 1 HDMI adaptor a single byte read will always give us
+	 * 0x44, and for a type 1 DVI adaptor it should give 0x00
+	 * (assuming it implements any registers). Fortunately neither
+	 * of those values will match the type 2 signature of the
+	 * DP_DUAL_MODE_ADAPTOR_ID register so we can proceed with
+	 * the type 2 adaptor detection safely even in the presence
+	 * of broken type 1 adaptors.
+	 */
+	ret = drm_dp_dual_mode_read(adapter, DP_DUAL_MODE_ADAPTOR_ID,
+				    &adaptor_id, sizeof(adaptor_id));
+	if (ret || (adaptor_id != (DP_DUAL_MODE_TYPE_TYPE2 |
+				   DP_DUAL_MODE_REV_TYPE2))) {
+		if (is_hdmi_adaptor(hdmi_id))
+			return DRM_DP_DUAL_MODE_TYPE1_HDMI;
+		else
+			return DRM_DP_DUAL_MODE_TYPE1_DVI;
+	} else {
+		if (is_hdmi_adaptor(hdmi_id))
+			return DRM_DP_DUAL_MODE_TYPE2_HDMI;
+		else
+			return DRM_DP_DUAL_MODE_TYPE2_DVI;
+	}
+}
+EXPORT_SYMBOL(drm_dp_dual_mode_detect);
+
+/**
+ * drm_dp_dual_mode_max_tmds_clock - Max TMDS clock for DP dual mode adaptor
+ * adapter: I2C adapter for the DDC bus
+ *
+ * Determine the max TMDS clock the adaptor supports based on the
+ * DP_DUAL_MODE_MAX_TMDS_CLOCK register. The register is mandatory for
+ * type 2 adaptors, optional for type 1 adaptors. Hoever, as some type 1
+ * adaptors are broken (see comments in drm_dp_dual_mode_detect() for the
+ * details) one probably shouldn't use this with type 1 adaptors at all.
+ * Type 1 adaptors should anyway be always limited to 165 MHz.
+ *
+ * Returns:
+ * Maximum supported TMDS clock rate for the DP dual mode adaptor in kHz.
+ */
+int drm_dp_dual_mode_max_tmds_clock(struct i2c_adapter *adapter)
+{
+	uint8_t max_tmds_clock;
+	ssize_t ret;
+
+	/*
+	 * Type 1 adaptors are limited to 165MHz
+	 * Type 2 adaptors can tells us their limit
+	 */
+	ret = drm_dp_dual_mode_read(adapter, DP_DUAL_MODE_MAX_TMDS_CLOCK,
+				    &max_tmds_clock, sizeof(max_tmds_clock));
+	if (ret)
+		return 165000;
+
+	return max_tmds_clock * 5000 / 2;
+}
+EXPORT_SYMBOL(drm_dp_dual_mode_max_tmds_clock);
+
+/**
+ * drm_dp_dual_mode_get_tmds_output - Get the state of the TMDS output buffers in the DP dual mode adaptor
+ * adapter: I2C adapter for the DDC bus
+ * enabled: current state of the TMDS output buffers
+ *
+ * Get the state of the TMDS output buffers in the adaptor.
+ * DP_DUAL_MODE_TMDS_OEN register is mandatory for type 2 adaptors,
+ * optionals for type 1 adaptors. Hoever, as some type 1 adaptors are
+ * broken (see comments in drm_dp_dual_mode_detect() for the details)
+ * one probably shouldn't use this with type 1 adaptors at all.
+ *
+ * Returns:
+ * 0 on success, negative error code on failure
+ */
+int drm_dp_dual_mode_get_tmds_output(struct i2c_adapter *adapter, bool *enabled)
+{
+	uint8_t tmds_oen;
+	ssize_t ret;
+
+	ret = drm_dp_dual_mode_read(adapter, DP_DUAL_MODE_TMDS_OEN,
+				    &tmds_oen, sizeof(tmds_oen));
+	if (ret)
+		return ret;
+
+	*enabled = !(tmds_oen & DP_DUAL_MODE_TMDS_DISABLE);
+
+	return 0;
+}
+EXPORT_SYMBOL(drm_dp_dual_mode_get_tmds_output);
+
+/**
+ * drm_dp_dual_mode_set_tmds_output - Enable/disable TMDS output buffers in the DP dual mode adaptor
+ * adapter: I2C adapter for the DDC bus
+ * enable: enable (as opposed to disable) the TMDS output buffers
+ *
+ * Set the state of the TMDS output buffers in the adaptor.
+ * DP_DUAL_MODE_TMDS_OEN register is mandatory for type 2 adaptors,
+ * optionals for type 1 adaptors. Hoever, as some type 1 adaptors are
+ * broken (see comments in drm_dp_dual_mode_detect() for the details)
+ * one probably shouldn't use this with type 1 adaptors at all.
+ *
+ * Returns:
+ * 0 on success, negative error code on failure
+ */
+int drm_dp_dual_mode_set_tmds_output(struct i2c_adapter *adapter, bool enable)
+{
+	uint8_t tmds_oen = enable ? 0 : DP_DUAL_MODE_TMDS_DISABLE;
+	ssize_t ret;
+
+	ret = drm_dp_dual_mode_write(adapter, DP_DUAL_MODE_TMDS_OEN,
+				     &tmds_oen, sizeof(tmds_oen));
+	if (ret)
+		return ret;
+
+	return 0;
+}
+EXPORT_SYMBOL(drm_dp_dual_mode_set_tmds_output);
+
+/**
+ * drm_dp_get_dual_mode_type_name - Get the name of the DP dual mode adaptor type as a string
+ * type: DP dual mode adaptor type
+ *
+ * Returns:
+ * String representation of the DP dual mode adaptor type
+ */
+const char *drm_dp_get_dual_mode_type_name(enum drm_dp_dual_mode_type type)
+{
+	switch (type) {
+	case DRM_DP_DUAL_MODE_NONE:
+		return "none";
+	case DRM_DP_DUAL_MODE_TYPE1_DVI:
+		return "type 1 DVI";
+	case DRM_DP_DUAL_MODE_TYPE1_HDMI:
+		return "type 1 HDMI";
+	case DRM_DP_DUAL_MODE_TYPE2_DVI:
+		return "type 2 DVI";
+	case DRM_DP_DUAL_MODE_TYPE2_HDMI:
+		return "type 2 HDMI";
+	default:
+		return "unknown";
+	};
+
+}
+EXPORT_SYMBOL(drm_dp_get_dual_mode_type_name);
diff --git a/include/drm/drm_dp_dual_mode_helper.h b/include/drm/drm_dp_dual_mode_helper.h
new file mode 100644
index 000000000000..a2f6b4587f5f
--- /dev/null
+++ b/include/drm/drm_dp_dual_mode_helper.h
@@ -0,0 +1,80 @@ 
+/*
+ * Copyright © 2016 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 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 COPYRIGHT HOLDER(S) OR AUTHOR(S) 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.
+ */
+
+#ifndef DRM_DP_DUAL_MODE_HELPER_H
+#define DRM_DP_DUAL_MODE_HELPER_H
+
+#include <linux/types.h>
+
+/*
+ * Optional for type 1 DVI adaptors
+ * Mandatory for type 1 HDMI and type 2 adators
+ */
+#define DP_DUAL_MODE_HDMI_ID 0x00 /* 00-0f */
+#define  DP_DUAL_MODE_HDMI_ID_LEN 16
+/*
+ * Optional for type 1 adaptors
+ * Mandatory for type 2 adators
+ */
+#define DP_DUAL_MODE_ADAPTOR_ID 0x10
+#define  DP_DUAL_MODE_REV_MASK 0x07
+#define  DP_DUAL_MODE_REV_TYPE2 0x00
+#define  DP_DUAL_MODE_TYPE_MASK 0xf0
+#define  DP_DUAL_MODE_TYPE_TYPE2 0xa0
+#define DP_DUAL_MODE_IEEE_OUI 0x11 /* 11-13*/
+#define  DP_DUAL_IEEE_OUI_LEN 3
+#define DP_DUAL_DEVICE_ID 0x14 /* 14-19 */
+#define  DP_DUAL_DEVICE_ID_LEN 6
+#define DP_DUAL_MODE_HARDWARE_REV 0x1a
+#define DP_DUAL_MODE_FIRMWARE_MAJOR_REV 0x1b
+#define DP_DUAL_MODE_FIRMWARE_MINOR_REV 0x1c
+#define DP_DUAL_MODE_MAX_TMDS_CLOCK 0x1d
+#define DP_DUAL_MODE_I2C_SPEED_CAP 0x1e
+#define DP_DUAL_MODE_TMDS_OEN 0x20
+#define  DP_DUAL_MODE_TMDS_DISABLE 0x01
+#define DP_DUAL_MODE_HDMI_PIN_CTRL 0x21
+#define  DP_DUAL_MODE_CEC_ENABLE 0x01
+#define DP_DUAL_MODE_I2C_SPEED_CTRL 0x22
+#define DP_DUAL_MODE_LAST_RESERVED 0xff
+
+struct i2c_adapter;
+
+ssize_t drm_dp_dual_mode_read(struct i2c_adapter *adapter,
+			      u8 offset, void *buffer, size_t size);
+ssize_t drm_dp_dual_mode_write(struct i2c_adapter *adapter,
+			       u8 offset, const void *buffer, size_t size);
+
+enum drm_dp_dual_mode_type {
+	DRM_DP_DUAL_MODE_NONE,
+	DRM_DP_DUAL_MODE_TYPE1_DVI,
+	DRM_DP_DUAL_MODE_TYPE1_HDMI,
+	DRM_DP_DUAL_MODE_TYPE2_DVI,
+	DRM_DP_DUAL_MODE_TYPE2_HDMI,
+};
+
+enum drm_dp_dual_mode_type drm_dp_dual_mode_detect(struct i2c_adapter *adapter);
+int drm_dp_dual_mode_max_tmds_clock(struct i2c_adapter *adapter);
+int drm_dp_dual_mode_get_tmds_output(struct i2c_adapter *adapter, bool *enabled);
+int drm_dp_dual_mode_set_tmds_output(struct i2c_adapter *adapter, bool enable);
+const char *drm_dp_get_dual_mode_type_name(enum drm_dp_dual_mode_type type);
+
+#endif

Comments

Em Ter, 2016-02-23 às 18:46 +0200, ville.syrjala@linux.intel.com
escreveu:
> From: Ville Syrjälä <ville.syrjala@linux.intel.com>

> 

> Add a helper which aids in he identification of DP dual mode (aka.

> DP++)

> adaptors. There are several types of adaptors specified:

> type 1 DVI, type 1 HDMI, type 2 DVI, type 2 HDMI

> 

> Type 1 adaptors have a max TMDS clock limit of 165MHz, type 2

> adaptors

> may go as high as 300MHz and they provide a register informing the

> source device what the actual limit is. Supposedly also type 1

> adaptors

> may optionally implement this register. This TMDS clock limit is the

> main reason why we need to identify these adaptors.

> 

> Type 1 adaptors provide access to their internal registers and the

> sink

> DDC bus through I2C. Type 2 adaptors provide this access both via I2C

> and I2C-over-AUX. A type 2 source device may choose to implement

> either

> or both of these methods. If a source device implements only the

> I2C-over-AUX method, then the driver will obviously need specific

> support for such adaptors since the port is driven like an HDMI port,

> but DDC communication happes over the AUX channel.

> 

> This helper should be enough to identify the adaptor type (some

> type 1 DVI adaptors may be a slight exception) and the maximum TMDS

> clock limit. Another feature that may be available is control over

> the TMDS output buffers on the adaptor, possibly allowing for some

> power saving when the TMDS link is down.

> 

> Other user controllable features that may be available in the

> adaptors

> are downstream i2c bus speed control when using i2c-over-aux, and

> some control over the CEC pin. I chose not to provide any helper

> functions for those since I have no use for them in i915 at this

> time.

> The rest of the registers in the adaptor are mostly just information,

> eg. IEEE OUI, hardware and firmware revision, etc.


Please run a spell checker and do some proof-reading both in the commit
message and in the code comments. Multiple instances of "sizo",
"Hoever", "adator", "Identyfy", etc. I also spotted some typos in the
next commits.



> Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>

> ---

>  drivers/gpu/drm/Makefile                  |   2 +-

>  drivers/gpu/drm/drm_dp_dual_mode_helper.c | 328

> ++++++++++++++++++++++++++++++

>  include/drm/drm_dp_dual_mode_helper.h     |  80 ++++++++

>  3 files changed, 409 insertions(+), 1 deletion(-)

>  create mode 100644 drivers/gpu/drm/drm_dp_dual_mode_helper.c

>  create mode 100644 include/drm/drm_dp_dual_mode_helper.h

> 

> diff --git a/drivers/gpu/drm/Makefile b/drivers/gpu/drm/Makefile

> index 6eb94fc561dc..22228ef50f36 100644

> --- a/drivers/gpu/drm/Makefile

> +++ b/drivers/gpu/drm/Makefile

> @@ -23,7 +23,7 @@ drm-$(CONFIG_AGP) += drm_agpsupport.o

>  

>  drm_kms_helper-y := drm_crtc_helper.o drm_dp_helper.o

> drm_probe_helper.o \

>  		drm_plane_helper.o drm_dp_mst_topology.o

> drm_atomic_helper.o \

> -		drm_kms_helper_common.o

> +		drm_kms_helper_common.o drm_dp_dual_mode_helper.o

>  

>  drm_kms_helper-$(CONFIG_DRM_LOAD_EDID_FIRMWARE) += drm_edid_load.o

>  drm_kms_helper-$(CONFIG_DRM_FBDEV_EMULATION) += drm_fb_helper.o

> diff --git a/drivers/gpu/drm/drm_dp_dual_mode_helper.c

> b/drivers/gpu/drm/drm_dp_dual_mode_helper.c

> new file mode 100644

> index 000000000000..bfe511c09568

> --- /dev/null

> +++ b/drivers/gpu/drm/drm_dp_dual_mode_helper.c

> @@ -0,0 +1,328 @@

> +/*

> + * Copyright © 2016 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 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 COPYRIGHT HOLDER(S) OR AUTHOR(S) 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/errno.h>

> +#include <linux/export.h>

> +#include <linux/i2c.h>

> +#include <linux/slab.h>

> +#include <linux/string.h>

> +#include <drm/drm_dp_dual_mode_helper.h>

> +#include <drm/drmP.h>

> +

> +/**

> + * DOC: DP dual mode (aka. DP++) adaptor helpers

> + *

> + * Helper functions to deal with DP dual mode adaptors.

> + *

> + * Type 1:

> + * Adaptor registers (if any) and the sink DDC bus may be accessed

> via I2C.

> + *

> + * Type 2:

> + * Adaptor registers and sink DDC bus can be accessed either via I2C

> or

> + * I2C-over-AUX. Source devices may choose to implement either one

> or

> + * both of these access methods.

> + */

> +

> +#define DP_DUAL_MODE_SLAVE_ADDRESS 0x40

> +

> +/**

> + * drm_dp_dual_mode_read - Read from the DP dual mode adaptor

> register(s)

> + * adapter: I2C adapter for the DDC bus

> + * offset: register offset

> + * buffer: buffer for return data

> + * size: sizo of the buffer

> + *

> + * Reads @size bytes from the DP dual mode adaptor registers

> + * starting at @offset.

> + *

> + * Returns:

> + * 0 on success, negative error code on failure

> + */

> +ssize_t drm_dp_dual_mode_read(struct i2c_adapter *adapter,

> +			      u8 offset, void *buffer, size_t size)

> +{

> +	struct i2c_msg msgs[] = {

> +		{

> +			.addr = DP_DUAL_MODE_SLAVE_ADDRESS,

> +			.flags = 0,

> +			.len = 1,

> +			.buf = &offset,

> +		},

> +		{

> +			.addr = DP_DUAL_MODE_SLAVE_ADDRESS,

> +			.flags = I2C_M_RD,

> +			.len = size,

> +			.buf = buffer,

> +		},

> +	};

> +	int ret;

> +

> +	ret = i2c_transfer(adapter, msgs, ARRAY_SIZE(msgs));

> +	if (ret < 0)

> +		return ret;

> +	if (ret != ARRAY_SIZE(msgs))

> +		return -EPROTO;


No retries needed here or below? (asking this due to the comment in
drm_edid.c about retries)

> +

> +	return 0;

> +}

> +

> +/**

> + * drm_dp_dual_mode_write - Write to the DP dual mode adaptor

> register(s)

> + * adapter: I2C adapter for the DDC bus

> + * offset: register offset

> + * buffer: buffer for write data

> + * size: sizo of the buffer

> + *

> + * Writes @size bytes to the DP dual mode adaptor registers

> + * starting at @offset.

> + *

> + * Returns:

> + * 0 on success, negative error code on failure

> + */

> +ssize_t drm_dp_dual_mode_write(struct i2c_adapter *adapter,

> +			       u8 offset, const void *buffer, size_t

> size)

> +{

> +	struct i2c_msg msg = {

> +		.addr = DP_DUAL_MODE_SLAVE_ADDRESS,

> +		.flags = 0,

> +		.len = 1 + size,

> +		.buf = NULL,

> +	};

> +	void *data;

> +	int ret;

> +

> +	data = kmalloc(msg.len, GFP_TEMPORARY);

> +	if (!data)

> +		return -ENOMEM;

> +

> +	msg.buf = data;

> +

> +	memcpy(data, &offset, 1);

> +	memcpy(data + 1, buffer, size);

> +

> +	ret = i2c_transfer(adapter, &msg, 1);

> +

> +	kfree(data);

> +

> +	if (ret < 0)

> +		return ret;

> +	if (ret != 1)

> +		return -EPROTO;

> +

> +	return 0;

> +}

> +EXPORT_SYMBOL(drm_dp_dual_mode_write);

> +

> +static bool is_hdmi_adaptor(const char

> hdmi_id[DP_DUAL_MODE_HDMI_ID_LEN])

> +{

> +	static const char

> dp_dual_mode_hdmi_id[DP_DUAL_MODE_HDMI_ID_LEN] =

> +		"DP-HDMI ADAPTOR\x04";

> +

> +	return memcmp(hdmi_id, dp_dual_mode_hdmi_id,

> +		      sizeof(dp_dual_mode_hdmi_id)) == 0;

> +}

> +

> +/**

> + * drm_dp_dual_mode_detect - Identyfy the DP dual mode adaptor

> + * adapter: I2C adapter for the DDC bus

> + *

> + * Attempt to identify the type of the DP dual mode adaptor used.

> + *

> + * Note that when the answer is @DRM_DP_DUAL_MODE_NONE it's not


So how about adding a new or just renaming it to
DRM_DP_DUAL_MODE_UNKNOWN? Let's not assume everybody is going to read
the docs.

> + * certain whether we're dealing with a native HDMI port or

> + * a type 1 DVI dual mode adaptor. The driver will have to use

> + * some other hardware/driver specific mechanism to make that

> + * distinction.

> + *

> + * Returns:

> + * The type of the DP dual mode adaptor used

> + */

> +enum drm_dp_dual_mode_type drm_dp_dual_mode_detect(struct

> i2c_adapter *adapter)

> +{

> +	char hdmi_id[DP_DUAL_MODE_HDMI_ID_LEN] = {};

> +	uint8_t adaptor_id = 0x00;

> +	ssize_t ret;

> +

> +	/*

> +	 * Let's see if the adaptor is there the by reading the

> +	 * HDMI ID registers.

> +	 *

> +	 * Note that type 1 DVI adaptors are not required to

> implemnt

> +	 * any registers, and that presents a problem for detection.

> +	 * If the i2c transfer is nacked, we may or may not be

> dealing

> +	 * with a type 1 DVI adaptor. Some other mechanism of

> detecting

> +	 * the presence of the adaptor is required. One way would be

> +	 * to check the state of the CONFIG1 pin, Another method

> would

> +	 * simply require the driver to know whether the port is a

> DP++

> +	 * port or a native HDMI port. Both of these methods are

> entirely

> +	 * hardware/driver specific so we can't deal with them here.

> +	 */

> +	ret = drm_dp_dual_mode_read(adapter, DP_DUAL_MODE_HDMI_ID,

> +				    hdmi_id, sizeof(hdmi_id));

> +	if (ret)

> +		return DRM_DP_DUAL_MODE_NONE;

> +

> +	/*

> +	 * Sigh. Some (maybe all?) type 1 adaptors are broken and

> ack

> +	 * the offset but ignore it, and instead they just always

> return

> +	 * data from the start of the HDMI ID buffer. So for a

> broken

> +	 * type 1 HDMI adaptor a single byte read will always give

> us

> +	 * 0x44, and for a type 1 DVI adaptor it should give 0x00

> +	 * (assuming it implements any registers).


So shouldn't we just try to read from 0x00 to 0x1F in a single shot?
Would this work for your specific adaptor? It would be interesting to
know.


>  Fortunately neither

> +	 * of those values will match the type 2 signature of the

> +	 * DP_DUAL_MODE_ADAPTOR_ID register so we can proceed with

> +	 * the type 2 adaptor detection safely even in the presence

> +	 * of broken type 1 adaptors.

> +	 */

> +	ret = drm_dp_dual_mode_read(adapter,

> DP_DUAL_MODE_ADAPTOR_ID,

> +				    &adaptor_id,

> sizeof(adaptor_id));

> +	if (ret || (adaptor_id != (DP_DUAL_MODE_TYPE_TYPE2 |

> +				   DP_DUAL_MODE_REV_TYPE2))) {

> +		if (is_hdmi_adaptor(hdmi_id))

> +			return DRM_DP_DUAL_MODE_TYPE1_HDMI;

> +		else

> +			return DRM_DP_DUAL_MODE_TYPE1_DVI;

> +	} else {

> +		if (is_hdmi_adaptor(hdmi_id))

> +			return DRM_DP_DUAL_MODE_TYPE2_HDMI;

> +		else

> +			return DRM_DP_DUAL_MODE_TYPE2_DVI;

> +	}

> +}

> +EXPORT_SYMBOL(drm_dp_dual_mode_detect);

> +

> +/**

> + * drm_dp_dual_mode_max_tmds_clock - Max TMDS clock for DP dual mode

> adaptor

> + * adapter: I2C adapter for the DDC bus

> + *

> + * Determine the max TMDS clock the adaptor supports based on the

> + * DP_DUAL_MODE_MAX_TMDS_CLOCK register. The register is mandatory

> for

> + * type 2 adaptors, optional for type 1 adaptors. Hoever, as some

> type 1

> + * adaptors are broken (see comments in drm_dp_dual_mode_detect()

> for the

> + * details) one probably shouldn't use this with type 1 adaptors at

> all.

> + * Type 1 adaptors should anyway be always limited to 165 MHz.


I always assume programmers are as bad as possible, so I wonder if we
should just also call drm_dp_dual_mode_detect() here. Also try the
trick of reading the whole thing at once instead of the specific
address. Same goes for the other functions. I also see that this would
make patches 2-4 different, so this is just an idea, not a requirement.

> + *

> + * Returns:

> + * Maximum supported TMDS clock rate for the DP dual mode adaptor in

> kHz.

> + */

> +int drm_dp_dual_mode_max_tmds_clock(struct i2c_adapter *adapter)

> +{

> +	uint8_t max_tmds_clock;

> +	ssize_t ret;

> +

> +	/*

> +	 * Type 1 adaptors are limited to 165MHz

> 

> +	 * Type 2 adaptors can tells us their limit


"can tells"

> +	 */

> +	ret = drm_dp_dual_mode_read(adapter,

> DP_DUAL_MODE_MAX_TMDS_CLOCK,

> +				    &max_tmds_clock,

> sizeof(max_tmds_clock));

> +	if (ret)


Maybe also "if (ret || max_tmds_clock == 0 || max_tmds_clock == 0xFF)"?


> +		return 165000;

> +

> +	return max_tmds_clock * 5000 / 2;

> +}

> +EXPORT_SYMBOL(drm_dp_dual_mode_max_tmds_clock);

> +

> +/**

> + * drm_dp_dual_mode_get_tmds_output - Get the state of the TMDS

> output buffers in the DP dual mode adaptor

> + * adapter: I2C adapter for the DDC bus

> + * enabled: current state of the TMDS output buffers

> + *

> + * Get the state of the TMDS output buffers in the adaptor.

> + * DP_DUAL_MODE_TMDS_OEN register is mandatory for type 2 adaptors,

> + * optionals for type 1 adaptors. Hoever, as some type 1 adaptors

> are

> + * broken (see comments in drm_dp_dual_mode_detect() for the

> details)

> + * one probably shouldn't use this with type 1 adaptors at all.

> + *

> + * Returns:

> + * 0 on success, negative error code on failure

> + */

> +int drm_dp_dual_mode_get_tmds_output(struct i2c_adapter *adapter,

> bool *enabled)

> +{

> +	uint8_t tmds_oen;

> +	ssize_t ret;

> +

> +	ret = drm_dp_dual_mode_read(adapter, DP_DUAL_MODE_TMDS_OEN,

> +				    &tmds_oen, sizeof(tmds_oen));

> +	if (ret)

> +		return ret;

> +

> +	*enabled = !(tmds_oen & DP_DUAL_MODE_TMDS_DISABLE);

> +

> +	return 0;

> +}

> +EXPORT_SYMBOL(drm_dp_dual_mode_get_tmds_output);

> +

> +/**

> + * drm_dp_dual_mode_set_tmds_output - Enable/disable TMDS output

> buffers in the DP dual mode adaptor

> + * adapter: I2C adapter for the DDC bus

> + * enable: enable (as opposed to disable) the TMDS output buffers

> + *

> + * Set the state of the TMDS output buffers in the adaptor.

> + * DP_DUAL_MODE_TMDS_OEN register is mandatory for type 2 adaptors,

> + * optionals for type 1 adaptors. Hoever, as some type 1 adaptors

> are

> + * broken (see comments in drm_dp_dual_mode_detect() for the

> details)

> + * one probably shouldn't use this with type 1 adaptors at all.

> + *

> + * Returns:

> + * 0 on success, negative error code on failure

> + */

> +int drm_dp_dual_mode_set_tmds_output(struct i2c_adapter *adapter,

> bool enable)

> +{

> +	uint8_t tmds_oen = enable ? 0 : DP_DUAL_MODE_TMDS_DISABLE;

> +	ssize_t ret;

> +

> +	ret = drm_dp_dual_mode_write(adapter, DP_DUAL_MODE_TMDS_OEN,

> +				     &tmds_oen, sizeof(tmds_oen));

> +	if (ret)

> +		return ret;

> +

> +	return 0;

> +}

> +EXPORT_SYMBOL(drm_dp_dual_mode_set_tmds_output);

> +

> +/**

> + * drm_dp_get_dual_mode_type_name - Get the name of the DP dual mode

> adaptor type as a string

> + * type: DP dual mode adaptor type

> + *

> + * Returns:

> + * String representation of the DP dual mode adaptor type

> + */

> +const char *drm_dp_get_dual_mode_type_name(enum

> drm_dp_dual_mode_type type)

> +{

> +	switch (type) {

> +	case DRM_DP_DUAL_MODE_NONE:

> +		return "none";

> +	case DRM_DP_DUAL_MODE_TYPE1_DVI:

> +		return "type 1 DVI";

> +	case DRM_DP_DUAL_MODE_TYPE1_HDMI:

> +		return "type 1 HDMI";

> +	case DRM_DP_DUAL_MODE_TYPE2_DVI:

> +		return "type 2 DVI";

> +	case DRM_DP_DUAL_MODE_TYPE2_HDMI:

> +		return "type 2 HDMI";

> +	default:

> +		return "unknown";


Please at least WARN_ON(1)?

And, if you implement my suggestion of adding an actual unknown value
to the enum, don't forget to change the default case to return
something that's not "unknown".

Most of the things I wrote above are just ideas, not requirements, and
having this patch as-is looks better than not having it, so if you at
least fix the spelling errors:

Reviewed-by: Paulo Zanoni <paulo.r.zanoni@intel.com>


> +	};

> +

> +}

> +EXPORT_SYMBOL(drm_dp_get_dual_mode_type_name);

> diff --git a/include/drm/drm_dp_dual_mode_helper.h

> b/include/drm/drm_dp_dual_mode_helper.h

> new file mode 100644

> index 000000000000..a2f6b4587f5f

> --- /dev/null

> +++ b/include/drm/drm_dp_dual_mode_helper.h

> @@ -0,0 +1,80 @@

> +/*

> + * Copyright © 2016 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 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 COPYRIGHT HOLDER(S) OR AUTHOR(S) 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.

> + */

> +

> +#ifndef DRM_DP_DUAL_MODE_HELPER_H

> +#define DRM_DP_DUAL_MODE_HELPER_H

> +

> +#include <linux/types.h>

> +

> +/*

> + * Optional for type 1 DVI adaptors

> + * Mandatory for type 1 HDMI and type 2 adators

> + */

> +#define DP_DUAL_MODE_HDMI_ID 0x00 /* 00-0f */

> +#define  DP_DUAL_MODE_HDMI_ID_LEN 16

> +/*

> + * Optional for type 1 adaptors

> + * Mandatory for type 2 adators

> + */

> +#define DP_DUAL_MODE_ADAPTOR_ID 0x10

> +#define  DP_DUAL_MODE_REV_MASK 0x07

> +#define  DP_DUAL_MODE_REV_TYPE2 0x00

> +#define  DP_DUAL_MODE_TYPE_MASK 0xf0

> +#define  DP_DUAL_MODE_TYPE_TYPE2 0xa0

> +#define DP_DUAL_MODE_IEEE_OUI 0x11 /* 11-13*/

> +#define  DP_DUAL_IEEE_OUI_LEN 3

> +#define DP_DUAL_DEVICE_ID 0x14 /* 14-19 */

> +#define  DP_DUAL_DEVICE_ID_LEN 6

> +#define DP_DUAL_MODE_HARDWARE_REV 0x1a

> +#define DP_DUAL_MODE_FIRMWARE_MAJOR_REV 0x1b

> +#define DP_DUAL_MODE_FIRMWARE_MINOR_REV 0x1c

> +#define DP_DUAL_MODE_MAX_TMDS_CLOCK 0x1d

> +#define DP_DUAL_MODE_I2C_SPEED_CAP 0x1e

> +#define DP_DUAL_MODE_TMDS_OEN 0x20

> +#define  DP_DUAL_MODE_TMDS_DISABLE 0x01

> +#define DP_DUAL_MODE_HDMI_PIN_CTRL 0x21

> +#define  DP_DUAL_MODE_CEC_ENABLE 0x01

> +#define DP_DUAL_MODE_I2C_SPEED_CTRL 0x22

> +#define DP_DUAL_MODE_LAST_RESERVED 0xff

> +

> +struct i2c_adapter;

> +

> +ssize_t drm_dp_dual_mode_read(struct i2c_adapter *adapter,

> +			      u8 offset, void *buffer, size_t size);

> +ssize_t drm_dp_dual_mode_write(struct i2c_adapter *adapter,

> +			       u8 offset, const void *buffer, size_t

> size);

> +

> +enum drm_dp_dual_mode_type {

> +	DRM_DP_DUAL_MODE_NONE,

> +	DRM_DP_DUAL_MODE_TYPE1_DVI,

> +	DRM_DP_DUAL_MODE_TYPE1_HDMI,

> +	DRM_DP_DUAL_MODE_TYPE2_DVI,

> +	DRM_DP_DUAL_MODE_TYPE2_HDMI,

> +};

> +

> +enum drm_dp_dual_mode_type drm_dp_dual_mode_detect(struct

> i2c_adapter *adapter);

> +int drm_dp_dual_mode_max_tmds_clock(struct i2c_adapter *adapter);

> +int drm_dp_dual_mode_get_tmds_output(struct i2c_adapter *adapter,

> bool *enabled);

> +int drm_dp_dual_mode_set_tmds_output(struct i2c_adapter *adapter,

> bool enable);

> +const char *drm_dp_get_dual_mode_type_name(enum

> drm_dp_dual_mode_type type);

> +

> +#endif
On Thu, Mar 31, 2016 at 07:25:36PM +0000, Zanoni, Paulo R wrote:
> Em Ter, 2016-02-23 às 18:46 +0200, ville.syrjala@linux.intel.com
> escreveu:
> > From: Ville Syrjälä <ville.syrjala@linux.intel.com>
> > 
> > Add a helper which aids in he identification of DP dual mode (aka.
> > DP++)
> > adaptors. There are several types of adaptors specified:
> > type 1 DVI, type 1 HDMI, type 2 DVI, type 2 HDMI
> > 
> > Type 1 adaptors have a max TMDS clock limit of 165MHz, type 2
> > adaptors
> > may go as high as 300MHz and they provide a register informing the
> > source device what the actual limit is. Supposedly also type 1
> > adaptors
> > may optionally implement this register. This TMDS clock limit is the
> > main reason why we need to identify these adaptors.
> > 
> > Type 1 adaptors provide access to their internal registers and the
> > sink
> > DDC bus through I2C. Type 2 adaptors provide this access both via I2C
> > and I2C-over-AUX. A type 2 source device may choose to implement
> > either
> > or both of these methods. If a source device implements only the
> > I2C-over-AUX method, then the driver will obviously need specific
> > support for such adaptors since the port is driven like an HDMI port,
> > but DDC communication happes over the AUX channel.
> > 
> > This helper should be enough to identify the adaptor type (some
> > type 1 DVI adaptors may be a slight exception) and the maximum TMDS
> > clock limit. Another feature that may be available is control over
> > the TMDS output buffers on the adaptor, possibly allowing for some
> > power saving when the TMDS link is down.
> > 
> > Other user controllable features that may be available in the
> > adaptors
> > are downstream i2c bus speed control when using i2c-over-aux, and
> > some control over the CEC pin. I chose not to provide any helper
> > functions for those since I have no use for them in i915 at this
> > time.
> > The rest of the registers in the adaptor are mostly just information,
> > eg. IEEE OUI, hardware and firmware revision, etc.
> 
> Please run a spell checker and do some proof-reading both in the commit
> message and in the code comments. Multiple instances of "sizo",
> "Hoever", "adator", "Identyfy", etc. I also spotted some typos in the
> next commits.
> 
> 
> 
> > Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
> > ---
> >  drivers/gpu/drm/Makefile                  |   2 +-
> >  drivers/gpu/drm/drm_dp_dual_mode_helper.c | 328
> > ++++++++++++++++++++++++++++++
> >  include/drm/drm_dp_dual_mode_helper.h     |  80 ++++++++
> >  3 files changed, 409 insertions(+), 1 deletion(-)
> >  create mode 100644 drivers/gpu/drm/drm_dp_dual_mode_helper.c
> >  create mode 100644 include/drm/drm_dp_dual_mode_helper.h
> > 
> > diff --git a/drivers/gpu/drm/Makefile b/drivers/gpu/drm/Makefile
> > index 6eb94fc561dc..22228ef50f36 100644
> > --- a/drivers/gpu/drm/Makefile
> > +++ b/drivers/gpu/drm/Makefile
> > @@ -23,7 +23,7 @@ drm-$(CONFIG_AGP) += drm_agpsupport.o
> >  
> >  drm_kms_helper-y := drm_crtc_helper.o drm_dp_helper.o
> > drm_probe_helper.o \
> >  		drm_plane_helper.o drm_dp_mst_topology.o
> > drm_atomic_helper.o \
> > -		drm_kms_helper_common.o
> > +		drm_kms_helper_common.o drm_dp_dual_mode_helper.o
> >  
> >  drm_kms_helper-$(CONFIG_DRM_LOAD_EDID_FIRMWARE) += drm_edid_load.o
> >  drm_kms_helper-$(CONFIG_DRM_FBDEV_EMULATION) += drm_fb_helper.o
> > diff --git a/drivers/gpu/drm/drm_dp_dual_mode_helper.c
> > b/drivers/gpu/drm/drm_dp_dual_mode_helper.c
> > new file mode 100644
> > index 000000000000..bfe511c09568
> > --- /dev/null
> > +++ b/drivers/gpu/drm/drm_dp_dual_mode_helper.c
> > @@ -0,0 +1,328 @@
> > +/*
> > + * Copyright © 2016 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 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 COPYRIGHT HOLDER(S) OR AUTHOR(S) 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/errno.h>
> > +#include <linux/export.h>
> > +#include <linux/i2c.h>
> > +#include <linux/slab.h>
> > +#include <linux/string.h>
> > +#include <drm/drm_dp_dual_mode_helper.h>
> > +#include <drm/drmP.h>
> > +
> > +/**
> > + * DOC: DP dual mode (aka. DP++) adaptor helpers
> > + *
> > + * Helper functions to deal with DP dual mode adaptors.
> > + *
> > + * Type 1:
> > + * Adaptor registers (if any) and the sink DDC bus may be accessed
> > via I2C.
> > + *
> > + * Type 2:
> > + * Adaptor registers and sink DDC bus can be accessed either via I2C
> > or
> > + * I2C-over-AUX. Source devices may choose to implement either one
> > or
> > + * both of these access methods.
> > + */
> > +
> > +#define DP_DUAL_MODE_SLAVE_ADDRESS 0x40
> > +
> > +/**
> > + * drm_dp_dual_mode_read - Read from the DP dual mode adaptor
> > register(s)
> > + * adapter: I2C adapter for the DDC bus
> > + * offset: register offset
> > + * buffer: buffer for return data
> > + * size: sizo of the buffer
> > + *
> > + * Reads @size bytes from the DP dual mode adaptor registers
> > + * starting at @offset.
> > + *
> > + * Returns:
> > + * 0 on success, negative error code on failure
> > + */
> > +ssize_t drm_dp_dual_mode_read(struct i2c_adapter *adapter,
> > +			      u8 offset, void *buffer, size_t size)
> > +{
> > +	struct i2c_msg msgs[] = {
> > +		{
> > +			.addr = DP_DUAL_MODE_SLAVE_ADDRESS,
> > +			.flags = 0,
> > +			.len = 1,
> > +			.buf = &offset,
> > +		},
> > +		{
> > +			.addr = DP_DUAL_MODE_SLAVE_ADDRESS,
> > +			.flags = I2C_M_RD,
> > +			.len = size,
> > +			.buf = buffer,
> > +		},
> > +	};
> > +	int ret;
> > +
> > +	ret = i2c_transfer(adapter, msgs, ARRAY_SIZE(msgs));
> > +	if (ret < 0)
> > +		return ret;
> > +	if (ret != ARRAY_SIZE(msgs))
> > +		return -EPROTO;
> 
> No retries needed here or below? (asking this due to the comment in
> drm_edid.c about retries)

The EDID retries are mostly cargo culted. I suspect you don't really
need them unless the connector is about to fall off, or the wiring
is made of cotton.

> 
> > +
> > +	return 0;
> > +}
> > +
> > +/**
> > + * drm_dp_dual_mode_write - Write to the DP dual mode adaptor
> > register(s)
> > + * adapter: I2C adapter for the DDC bus
> > + * offset: register offset
> > + * buffer: buffer for write data
> > + * size: sizo of the buffer
> > + *
> > + * Writes @size bytes to the DP dual mode adaptor registers
> > + * starting at @offset.
> > + *
> > + * Returns:
> > + * 0 on success, negative error code on failure
> > + */
> > +ssize_t drm_dp_dual_mode_write(struct i2c_adapter *adapter,
> > +			       u8 offset, const void *buffer, size_t
> > size)
> > +{
> > +	struct i2c_msg msg = {
> > +		.addr = DP_DUAL_MODE_SLAVE_ADDRESS,
> > +		.flags = 0,
> > +		.len = 1 + size,
> > +		.buf = NULL,
> > +	};
> > +	void *data;
> > +	int ret;
> > +
> > +	data = kmalloc(msg.len, GFP_TEMPORARY);
> > +	if (!data)
> > +		return -ENOMEM;
> > +
> > +	msg.buf = data;
> > +
> > +	memcpy(data, &offset, 1);
> > +	memcpy(data + 1, buffer, size);
> > +
> > +	ret = i2c_transfer(adapter, &msg, 1);
> > +
> > +	kfree(data);
> > +
> > +	if (ret < 0)
> > +		return ret;
> > +	if (ret != 1)
> > +		return -EPROTO;
> > +
> > +	return 0;
> > +}
> > +EXPORT_SYMBOL(drm_dp_dual_mode_write);
> > +
> > +static bool is_hdmi_adaptor(const char
> > hdmi_id[DP_DUAL_MODE_HDMI_ID_LEN])
> > +{
> > +	static const char
> > dp_dual_mode_hdmi_id[DP_DUAL_MODE_HDMI_ID_LEN] =
> > +		"DP-HDMI ADAPTOR\x04";
> > +
> > +	return memcmp(hdmi_id, dp_dual_mode_hdmi_id,
> > +		      sizeof(dp_dual_mode_hdmi_id)) == 0;
> > +}
> > +
> > +/**
> > + * drm_dp_dual_mode_detect - Identyfy the DP dual mode adaptor
> > + * adapter: I2C adapter for the DDC bus
> > + *
> > + * Attempt to identify the type of the DP dual mode adaptor used.
> > + *
> > + * Note that when the answer is @DRM_DP_DUAL_MODE_NONE it's not
> 
> So how about adding a new or just renaming it to
> DRM_DP_DUAL_MODE_UNKNOWN? Let's not assume everybody is going to read
> the docs.

I suppose adding an extra enum value can't hurt.

> 
> > + * certain whether we're dealing with a native HDMI port or
> > + * a type 1 DVI dual mode adaptor. The driver will have to use
> > + * some other hardware/driver specific mechanism to make that
> > + * distinction.
> > + *
> > + * Returns:
> > + * The type of the DP dual mode adaptor used
> > + */
> > +enum drm_dp_dual_mode_type drm_dp_dual_mode_detect(struct
> > i2c_adapter *adapter)
> > +{
> > +	char hdmi_id[DP_DUAL_MODE_HDMI_ID_LEN] = {};
> > +	uint8_t adaptor_id = 0x00;
> > +	ssize_t ret;
> > +
> > +	/*
> > +	 * Let's see if the adaptor is there the by reading the
> > +	 * HDMI ID registers.
> > +	 *
> > +	 * Note that type 1 DVI adaptors are not required to
> > implemnt
> > +	 * any registers, and that presents a problem for detection.
> > +	 * If the i2c transfer is nacked, we may or may not be
> > dealing
> > +	 * with a type 1 DVI adaptor. Some other mechanism of
> > detecting
> > +	 * the presence of the adaptor is required. One way would be
> > +	 * to check the state of the CONFIG1 pin, Another method
> > would
> > +	 * simply require the driver to know whether the port is a
> > DP++
> > +	 * port or a native HDMI port. Both of these methods are
> > entirely
> > +	 * hardware/driver specific so we can't deal with them here.
> > +	 */
> > +	ret = drm_dp_dual_mode_read(adapter, DP_DUAL_MODE_HDMI_ID,
> > +				    hdmi_id, sizeof(hdmi_id));
> > +	if (ret)
> > +		return DRM_DP_DUAL_MODE_NONE;
> > +
> > +	/*
> > +	 * Sigh. Some (maybe all?) type 1 adaptors are broken and
> > ack
> > +	 * the offset but ignore it, and instead they just always
> > return
> > +	 * data from the start of the HDMI ID buffer. So for a
> > broken
> > +	 * type 1 HDMI adaptor a single byte read will always give
> > us
> > +	 * 0x44, and for a type 1 DVI adaptor it should give 0x00
> > +	 * (assuming it implements any registers).
> 
> So shouldn't we just try to read from 0x00 to 0x1F in a single shot?
> Would this work for your specific adaptor? It would be interesting to
> know.

I think I did consider that after giving up on another strange detection
scheme that would have perhaps allowed me to detect decent type 1
adaptors. IIRC the adaptors I tested returned 0x00 or 0xff for the
0x10-0x20 range when doing a single read, but I suspect they might as
well just wrap after 0x0f since the spec says they don't need to implement
anything beyond 0x00-0x0f. While all of those results would work just as
well as reading the single byte, I decided that there's no point in doing
that since I had not seem a single sane type 1 adaptor. They're clearly
all just bottom of the barrel hardware so seems unlikely anyone would
go to the effort of implementing one decently. So in the end I just
figured that minimizing the amount of data we have to read is the sane
thing to do.

> 
> 
> >  Fortunately neither
> > +	 * of those values will match the type 2 signature of the
> > +	 * DP_DUAL_MODE_ADAPTOR_ID register so we can proceed with
> > +	 * the type 2 adaptor detection safely even in the presence
> > +	 * of broken type 1 adaptors.
> > +	 */
> > +	ret = drm_dp_dual_mode_read(adapter,
> > DP_DUAL_MODE_ADAPTOR_ID,
> > +				    &adaptor_id,
> > sizeof(adaptor_id));
> > +	if (ret || (adaptor_id != (DP_DUAL_MODE_TYPE_TYPE2 |
> > +				   DP_DUAL_MODE_REV_TYPE2))) {
> > +		if (is_hdmi_adaptor(hdmi_id))
> > +			return DRM_DP_DUAL_MODE_TYPE1_HDMI;
> > +		else
> > +			return DRM_DP_DUAL_MODE_TYPE1_DVI;
> > +	} else {
> > +		if (is_hdmi_adaptor(hdmi_id))
> > +			return DRM_DP_DUAL_MODE_TYPE2_HDMI;
> > +		else
> > +			return DRM_DP_DUAL_MODE_TYPE2_DVI;
> > +	}
> > +}
> > +EXPORT_SYMBOL(drm_dp_dual_mode_detect);
> > +
> > +/**
> > + * drm_dp_dual_mode_max_tmds_clock - Max TMDS clock for DP dual mode
> > adaptor
> > + * adapter: I2C adapter for the DDC bus
> > + *
> > + * Determine the max TMDS clock the adaptor supports based on the
> > + * DP_DUAL_MODE_MAX_TMDS_CLOCK register. The register is mandatory
> > for
> > + * type 2 adaptors, optional for type 1 adaptors. Hoever, as some
> > type 1
> > + * adaptors are broken (see comments in drm_dp_dual_mode_detect()
> > for the
> > + * details) one probably shouldn't use this with type 1 adaptors at
> > all.
> > + * Type 1 adaptors should anyway be always limited to 165 MHz.
> 
> I always assume programmers are as bad as possible, so I wonder if we
> should just also call drm_dp_dual_mode_detect() here.

This crossed my mind but I didn't want to slow down things needlessly.

I did in fact consider that we might want to raise the abstraction
level a bit and introduce some kind of dp_dual_mode object that keeps
around the relevant information/state and would allow drivers to avoid
the type checks and whatnot. Unfortunately those cursed type 1 DVI
adaptors would still require the driver to step in if the detection
fails to find anything, so we'd need a callback into the driver or
something.

And so, since the driver anyway has to deal with the type 1 DVI adaptors,
I decided that trying to hide these sort of details inside the helper
is pretty much pointless.

> Also try the
> trick of reading the whole thing at once instead of the specific
> address. Same goes for the other functions. I also see that this would
> make patches 2-4 different, so this is just an idea, not a requirement.

As I suspect some adaptors might just wrap around at 0xf, doing a
big read doesn't feel entirely safe here.

> 
> > + *
> > + * Returns:
> > + * Maximum supported TMDS clock rate for the DP dual mode adaptor in
> > kHz.
> > + */
> > +int drm_dp_dual_mode_max_tmds_clock(struct i2c_adapter *adapter)
> > +{
> > +	uint8_t max_tmds_clock;
> > +	ssize_t ret;
> > +
> > +	/*
> > +	 * Type 1 adaptors are limited to 165MHz
> > 
> > +	 * Type 2 adaptors can tells us their limit
> 
> "can tells"
> 
> > +	 */
> > +	ret = drm_dp_dual_mode_read(adapter,
> > DP_DUAL_MODE_MAX_TMDS_CLOCK,
> > +				    &max_tmds_clock,
> > sizeof(max_tmds_clock));
> > +	if (ret)
> 
> Maybe also "if (ret || max_tmds_clock == 0 || max_tmds_clock == 0xFF)"?

That would seem sensible indeed.

> 
> 
> > +		return 165000;
> > +
> > +	return max_tmds_clock * 5000 / 2;
> > +}
> > +EXPORT_SYMBOL(drm_dp_dual_mode_max_tmds_clock);
> > +
> > +/**
> > + * drm_dp_dual_mode_get_tmds_output - Get the state of the TMDS
> > output buffers in the DP dual mode adaptor
> > + * adapter: I2C adapter for the DDC bus
> > + * enabled: current state of the TMDS output buffers
> > + *
> > + * Get the state of the TMDS output buffers in the adaptor.
> > + * DP_DUAL_MODE_TMDS_OEN register is mandatory for type 2 adaptors,
> > + * optionals for type 1 adaptors. Hoever, as some type 1 adaptors
> > are
> > + * broken (see comments in drm_dp_dual_mode_detect() for the
> > details)
> > + * one probably shouldn't use this with type 1 adaptors at all.
> > + *
> > + * Returns:
> > + * 0 on success, negative error code on failure
> > + */
> > +int drm_dp_dual_mode_get_tmds_output(struct i2c_adapter *adapter,
> > bool *enabled)
> > +{
> > +	uint8_t tmds_oen;
> > +	ssize_t ret;
> > +
> > +	ret = drm_dp_dual_mode_read(adapter, DP_DUAL_MODE_TMDS_OEN,
> > +				    &tmds_oen, sizeof(tmds_oen));
> > +	if (ret)
> > +		return ret;
> > +
> > +	*enabled = !(tmds_oen & DP_DUAL_MODE_TMDS_DISABLE);
> > +
> > +	return 0;
> > +}
> > +EXPORT_SYMBOL(drm_dp_dual_mode_get_tmds_output);
> > +
> > +/**
> > + * drm_dp_dual_mode_set_tmds_output - Enable/disable TMDS output
> > buffers in the DP dual mode adaptor
> > + * adapter: I2C adapter for the DDC bus
> > + * enable: enable (as opposed to disable) the TMDS output buffers
> > + *
> > + * Set the state of the TMDS output buffers in the adaptor.
> > + * DP_DUAL_MODE_TMDS_OEN register is mandatory for type 2 adaptors,
> > + * optionals for type 1 adaptors. Hoever, as some type 1 adaptors
> > are
> > + * broken (see comments in drm_dp_dual_mode_detect() for the
> > details)
> > + * one probably shouldn't use this with type 1 adaptors at all.
> > + *
> > + * Returns:
> > + * 0 on success, negative error code on failure
> > + */
> > +int drm_dp_dual_mode_set_tmds_output(struct i2c_adapter *adapter,
> > bool enable)
> > +{
> > +	uint8_t tmds_oen = enable ? 0 : DP_DUAL_MODE_TMDS_DISABLE;
> > +	ssize_t ret;
> > +
> > +	ret = drm_dp_dual_mode_write(adapter, DP_DUAL_MODE_TMDS_OEN,
> > +				     &tmds_oen, sizeof(tmds_oen));
> > +	if (ret)
> > +		return ret;
> > +
> > +	return 0;
> > +}
> > +EXPORT_SYMBOL(drm_dp_dual_mode_set_tmds_output);
> > +
> > +/**
> > + * drm_dp_get_dual_mode_type_name - Get the name of the DP dual mode
> > adaptor type as a string
> > + * type: DP dual mode adaptor type
> > + *
> > + * Returns:
> > + * String representation of the DP dual mode adaptor type
> > + */
> > +const char *drm_dp_get_dual_mode_type_name(enum
> > drm_dp_dual_mode_type type)
> > +{
> > +	switch (type) {
> > +	case DRM_DP_DUAL_MODE_NONE:
> > +		return "none";
> > +	case DRM_DP_DUAL_MODE_TYPE1_DVI:
> > +		return "type 1 DVI";
> > +	case DRM_DP_DUAL_MODE_TYPE1_HDMI:
> > +		return "type 1 HDMI";
> > +	case DRM_DP_DUAL_MODE_TYPE2_DVI:
> > +		return "type 2 DVI";
> > +	case DRM_DP_DUAL_MODE_TYPE2_HDMI:
> > +		return "type 2 HDMI";
> > +	default:
> > +		return "unknown";
> 
> Please at least WARN_ON(1)?

We don't generally warn in these case (in the drm core).

> 
> And, if you implement my suggestion of adding an actual unknown value
> to the enum, don't forget to change the default case to return
> something that's not "unknown".
> 
> Most of the things I wrote above are just ideas, not requirements, and
> having this patch as-is looks better than not having it, so if you at
> least fix the spelling errors:
> 
> Reviewed-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
> 
> > +	};
> > +
> > +}
> > +EXPORT_SYMBOL(drm_dp_get_dual_mode_type_name);
> > diff --git a/include/drm/drm_dp_dual_mode_helper.h
> > b/include/drm/drm_dp_dual_mode_helper.h
> > new file mode 100644
> > index 000000000000..a2f6b4587f5f
> > --- /dev/null
> > +++ b/include/drm/drm_dp_dual_mode_helper.h
> > @@ -0,0 +1,80 @@
> > +/*
> > + * Copyright © 2016 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 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 COPYRIGHT HOLDER(S) OR AUTHOR(S) 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.
> > + */
> > +
> > +#ifndef DRM_DP_DUAL_MODE_HELPER_H
> > +#define DRM_DP_DUAL_MODE_HELPER_H
> > +
> > +#include <linux/types.h>
> > +
> > +/*
> > + * Optional for type 1 DVI adaptors
> > + * Mandatory for type 1 HDMI and type 2 adators
> > + */
> > +#define DP_DUAL_MODE_HDMI_ID 0x00 /* 00-0f */
> > +#define  DP_DUAL_MODE_HDMI_ID_LEN 16
> > +/*
> > + * Optional for type 1 adaptors
> > + * Mandatory for type 2 adators
> > + */
> > +#define DP_DUAL_MODE_ADAPTOR_ID 0x10
> > +#define  DP_DUAL_MODE_REV_MASK 0x07
> > +#define  DP_DUAL_MODE_REV_TYPE2 0x00
> > +#define  DP_DUAL_MODE_TYPE_MASK 0xf0
> > +#define  DP_DUAL_MODE_TYPE_TYPE2 0xa0
> > +#define DP_DUAL_MODE_IEEE_OUI 0x11 /* 11-13*/
> > +#define  DP_DUAL_IEEE_OUI_LEN 3
> > +#define DP_DUAL_DEVICE_ID 0x14 /* 14-19 */
> > +#define  DP_DUAL_DEVICE_ID_LEN 6
> > +#define DP_DUAL_MODE_HARDWARE_REV 0x1a
> > +#define DP_DUAL_MODE_FIRMWARE_MAJOR_REV 0x1b
> > +#define DP_DUAL_MODE_FIRMWARE_MINOR_REV 0x1c
> > +#define DP_DUAL_MODE_MAX_TMDS_CLOCK 0x1d
> > +#define DP_DUAL_MODE_I2C_SPEED_CAP 0x1e
> > +#define DP_DUAL_MODE_TMDS_OEN 0x20
> > +#define  DP_DUAL_MODE_TMDS_DISABLE 0x01
> > +#define DP_DUAL_MODE_HDMI_PIN_CTRL 0x21
> > +#define  DP_DUAL_MODE_CEC_ENABLE 0x01
> > +#define DP_DUAL_MODE_I2C_SPEED_CTRL 0x22
> > +#define DP_DUAL_MODE_LAST_RESERVED 0xff
> > +
> > +struct i2c_adapter;
> > +
> > +ssize_t drm_dp_dual_mode_read(struct i2c_adapter *adapter,
> > +			      u8 offset, void *buffer, size_t size);
> > +ssize_t drm_dp_dual_mode_write(struct i2c_adapter *adapter,
> > +			       u8 offset, const void *buffer, size_t
> > size);
> > +
> > +enum drm_dp_dual_mode_type {
> > +	DRM_DP_DUAL_MODE_NONE,
> > +	DRM_DP_DUAL_MODE_TYPE1_DVI,
> > +	DRM_DP_DUAL_MODE_TYPE1_HDMI,
> > +	DRM_DP_DUAL_MODE_TYPE2_DVI,
> > +	DRM_DP_DUAL_MODE_TYPE2_HDMI,
> > +};
> > +
> > +enum drm_dp_dual_mode_type drm_dp_dual_mode_detect(struct
> > i2c_adapter *adapter);
> > +int drm_dp_dual_mode_max_tmds_clock(struct i2c_adapter *adapter);
> > +int drm_dp_dual_mode_get_tmds_output(struct i2c_adapter *adapter,
> > bool *enabled);
> > +int drm_dp_dual_mode_set_tmds_output(struct i2c_adapter *adapter,
> > bool enable);
> > +const char *drm_dp_get_dual_mode_type_name(enum
> > drm_dp_dual_mode_type type);
> > +
> > +#endif