[APPLIED] System76 - Intel DRM patch

Andy Whitcroft apw at canonical.com
Mon Apr 2 16:12:15 UTC 2012

Applied to Precise.  Patch was in drm-intel pending merge.  I have
included the patch as applied below for completeness.


>From 8b8ec63a0a5e44df4eee6f302da41ee9c9fc871b Mon Sep 17 00:00:00 2001
From: Chris Wilson <chris at chris-wilson.co.uk>
Date: Thu, 22 Mar 2012 15:00:50 +0000
Subject: [PATCH] drm/i915: Sanitize BIOS debugging bits from PIPECONF

Quoting the BSpec from time immemorial:

  PIPEACONF, bits 28:27: Frame Start Delay (Debug)

  Used to delay the frame start signal that is sent to the display planes.
  Care must be taken to insure that there are enough lines during VBLANK
  to support this setting.

An instance of the BIOS leaving these bits set was found in the wild,
where it caused our modesetting to go all squiffy and skewiff.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=47271
Reported-and-tested-by: Eva Wang <evawang at linpus.com>
Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=43012
Reported-and-tested-by: Carl Richell <carl at system76.com>
Cc: stable at kernel.org
Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
Signed-off-by: Daniel Vetter <daniel.vetter at ffwll.ch>

(cherry-picked from commit f47166d2b0001fcb752b40c5a2d4db986dfbea68 drm-intel)
BugLink: http://bugs.launchpad.net/bugs/968307
Acked-by: Robert Hooker <sarvatt at canonical.com>
Signed-off-by: Andy Whitcroft <apw at canonical.com>
 drivers/gpu/drm/i915/i915_reg.h      |    1 +
 drivers/gpu/drm/i915/intel_display.c |    6 ++++++
 2 files changed, 7 insertions(+), 0 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
index 1608d2a..2f99fd4 100644
--- a/drivers/gpu/drm/i915/i915_reg.h
+++ b/drivers/gpu/drm/i915/i915_reg.h
@@ -2312,6 +2312,7 @@
 #define   PIPECONF_DOUBLE_WIDE	(1<<30)
 #define   I965_PIPECONF_ACTIVE	(1<<30)
 #define   PIPECONF_PIPE_LOCKED	(1<<25)
diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index 5b203df..28bf5fb 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -7281,6 +7281,12 @@ static void intel_sanitize_modesetting(struct drm_device *dev,
 	struct drm_i915_private *dev_priv = dev->dev_private;
 	u32 reg, val;
+	/* Clear any frame start delays used for debugging left by the BIOS */
+	for_each_pipe(pipe) {
+		reg = PIPECONF(pipe);
+	}
 	if (HAS_PCH_SPLIT(dev))

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