Fix resume from suspend to RAM on IBM X30 (take two)

Submitted by Thomas Richter on June 1, 2015, 8:25 a.m.

Details

Message ID 556C16E6.2040309@math.tu-berlin.de
State New
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Commit Message

Thomas Richter June 1, 2015, 8:25 a.m.
Hi Daniel, hi Ville,

as suggested, I again checked against the latest drm-intel-nightly
branch and indeed, the patch as originally submitted does not apply
there. So I recompiled the patch again (see attachment) which works now
correctly with the latest branch.

As suggested, I made a couple of additional changes:

* No longer forces bit-banging on. As Daniel observed, this is not
really required, and I checked that, indeed, it is not.

* Ville made a comment a while ago that we should not enable the
extended panel-scaling of the IVCH, so I removed it. In fact, as the X30
bios does not restore registers during resume, it also fails to restore
the (undocumented) values of the advanced interpolation polynomials and
as such degrades the image quality when resuming from suspend.

Other than that, this patch has been successfully tested both on an IBM
X30 and on an IBM R31 ThinkPad, both making use of the IVCH DVO chip.

Greetings,
	Thomas

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From 457d52863d4dfb9d68091fca5716560dd4eb4441 Mon Sep 17 00:00:00 2001
From: Thomas Richter <thor@math.tu-berlin.de>
Date: Sat, 30 May 2015 20:25:53 +0200
Subject: [PATCH 1/1] Fix resume from suspend on IBM X30

This patch fixes the resume from suspend-to-ram on the IBM X30
laptop. The problem is caused by the Bios missing to re-initialize
the iVCH registers, especially the PLL registers.

This patch records the iVCH registers during initialization, and
re-installs this register set when resuming.

Signed-off-by: Thomas Richter <thor@math.tu-berlin.de>
---
 drivers/gpu/drm/i915/dvo_ivch.c |   63 +++++++++++++++++++++++++++++++++++----
 1 file changed, 57 insertions(+), 6 deletions(-)

diff --git a/drivers/gpu/drm/i915/dvo_ivch.c b/drivers/gpu/drm/i915/dvo_ivch.c
index 89b08a8..732ce87 100644
--- a/drivers/gpu/drm/i915/dvo_ivch.c
+++ b/drivers/gpu/drm/i915/dvo_ivch.c
@@ -22,6 +22,7 @@ 
  *
  * Authors:
  *    Eric Anholt <eric@anholt.net>
+ *    Thomas Richter <thor@math.tu-berlin.de>
  *
  * Minor modifications (Dithering enable):
  *    Thomas Richter <thor@math.tu-berlin.de>
@@ -90,7 +91,7 @@ 
 /*
  * LCD Vertical Display Size
  */
-#define VR21	0x20
+#define VR21	0x21
 
 /*
  * Panel power down status
@@ -155,16 +156,33 @@ 
 # define VR8F_POWER_MASK		(0x3c)
 # define VR8F_POWER_POS			(2)
 
+/* Some Bios implementations do not restore the DVO state upon
+ * resume from standby. Thus, this driver has to handle it
+ * instead. The following list contains all registers that
+ * require saving.
+ */
+static const uint16_t backup_addresses[] = {
+	0x11, 0x12,
+	0x18, 0x19, 0x1a, 0x1f,
+	0x20, 0x21, 0x22, 0x23, 0x24, 0x25, 0x26, 0x27,
+	0x31, 0x32, 0x33, 0x34, 0x35, 0x36, 0x37,
+	0x8e, 0x8f,
+	0x10		/* this must come last */
+};
+
 
 struct ivch_priv {
 	bool quiet;
 
 	uint16_t width, height;
+
+	/* Register backup */
+
+	uint16_t reg_backup[ARRAY_SIZE(backup_addresses)];
 };
 
 
 static void ivch_dump_regs(struct intel_dvo_device *dvo);
-
 /**
  * Reads a register on the ivch.
  *
@@ -246,6 +264,7 @@  static bool ivch_init(struct intel_dvo_device *dvo,
 {
 	struct ivch_priv *priv;
 	uint16_t temp;
+	int i;
 
 	priv = kzalloc(sizeof(struct ivch_priv), GFP_KERNEL);
 	if (priv == NULL)
@@ -273,6 +292,14 @@  static bool ivch_init(struct intel_dvo_device *dvo,
 	ivch_read(dvo, VR20, &priv->width);
 	ivch_read(dvo, VR21, &priv->height);
 
+	/* Make a backup of the registers to be able to restore them
+	 * upon suspend.
+	 */
+	for (i = 0; i < ARRAY_SIZE(backup_addresses); i++)
+		ivch_read(dvo, backup_addresses[i], priv->reg_backup + i);
+
+	ivch_dump_regs(dvo);
+
 	return true;
 
 out:
@@ -294,12 +321,31 @@  static enum drm_mode_status ivch_mode_valid(struct intel_dvo_device *dvo,
 	return MODE_OK;
 }
 
+/* Restore the DVO registers after a resume
+ * from RAM. Registers have been saved during
+ * the initialization.
+ */
+static void ivch_reset(struct intel_dvo_device *dvo)
+{
+	struct ivch_priv *priv = dvo->dev_priv;
+	int i;
+
+	DRM_DEBUG_KMS("Resetting the IVCH registers\n");
+
+	ivch_write(dvo, VR10, 0x0000);
+
+	for (i = 0; i < ARRAY_SIZE(backup_addresses); i++)
+		ivch_write(dvo, backup_addresses[i], priv->reg_backup[i]);
+}
+
 /** Sets the power state of the panel connected to the ivch */
 static void ivch_dpms(struct intel_dvo_device *dvo, bool enable)
 {
 	int i;
 	uint16_t vr01, vr30, backlight;
 
+	ivch_reset(dvo);
+
 	/* Set the new power state of the panel. */
 	if (!ivch_read(dvo, VR01, &vr01))
 		return;
@@ -308,6 +354,7 @@  static void ivch_dpms(struct intel_dvo_device *dvo, bool enable)
 		backlight = 1;
 	else
 		backlight = 0;
+
 	ivch_write(dvo, VR80, backlight);
 
 	if (enable)
@@ -334,6 +381,8 @@  static bool ivch_get_hw_state(struct intel_dvo_device *dvo)
 {
 	uint16_t vr01;
 
+	ivch_reset(dvo);
+
 	/* Set the new power state of the panel. */
 	if (!ivch_read(dvo, VR01, &vr01))
 		return false;
@@ -348,11 +397,15 @@  static void ivch_mode_set(struct intel_dvo_device *dvo,
 			  struct drm_display_mode *mode,
 			  struct drm_display_mode *adjusted_mode)
 {
+	struct ivch_priv *priv = dvo->dev_priv;
 	uint16_t vr40 = 0;
 	uint16_t vr01 = 0;
 	uint16_t vr10;
 
-	ivch_read(dvo, VR10, &vr10);
+	ivch_reset(dvo);
+
+	vr10 = priv->reg_backup[ARRAY_SIZE(backup_addresses) - 1];
+
 	/* Enable dithering for 18 bpp pipelines */
 	vr10 &= VR10_INTERFACE_DEPTH_MASK;
 	if (vr10 == VR10_INTERFACE_2X18 || vr10 == VR10_INTERFACE_1X18)
@@ -366,7 +419,7 @@  static void ivch_mode_set(struct intel_dvo_device *dvo,
 		uint16_t x_ratio, y_ratio;
 
 		vr01 |= VR01_PANEL_FIT_ENABLE;
-		vr40 |= VR40_CLOCK_GATING_ENABLE | VR40_ENHANCED_PANEL_FITTING;
+		vr40 |= VR40_CLOCK_GATING_ENABLE;
 		x_ratio = (((mode->hdisplay - 1) << 16) /
 			   (adjusted_mode->hdisplay - 1)) >> 2;
 		y_ratio = (((mode->vdisplay - 1) << 16) /
@@ -381,8 +434,6 @@  static void ivch_mode_set(struct intel_dvo_device *dvo,
 
 	ivch_write(dvo, VR01, vr01);
 	ivch_write(dvo, VR40, vr40);
-
-	ivch_dump_regs(dvo);
 }
 
 static void ivch_dump_regs(struct intel_dvo_device *dvo)
-- 
1.7.10.4


Comments

On Mon, Jun 01, 2015 at 10:25:10AM +0200, Thomas Richter wrote:
> Hi Daniel, hi Ville,
> 
> as suggested, I again checked against the latest drm-intel-nightly
> branch and indeed, the patch as originally submitted does not apply
> there. So I recompiled the patch again (see attachment) which works now
> correctly with the latest branch.
> 
> As suggested, I made a couple of additional changes:
> 
> * No longer forces bit-banging on. As Daniel observed, this is not
> really required, and I checked that, indeed, it is not.
> 
> * Ville made a comment a while ago that we should not enable the
> extended panel-scaling of the IVCH, so I removed it. In fact, as the X30
> bios does not restore registers during resume, it also fails to restore
> the (undocumented) values of the advanced interpolation polynomials and
> as such degrades the image quality when resuming from suspend.
> 
> Other than that, this patch has been successfully tested both on an IBM
> X30 and on an IBM R31 ThinkPad, both making use of the IVCH DVO chip.

Yup this one applies cleanly now. Queued for -next, thanks for the patch.
-Daniel
> Yup this one applies cleanly now. Queued for -next, thanks for the patch.

Yay!  Thanks!


        Stefan