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drm/i915: Sanitize BIOS debugging bits from PIPECONF

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commit f47166d2b0 upstream.

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@linpus.com>
Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=43012
Reported-and-tested-by: Carl Richell <carl@system76.com>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Chris Wilson
2012-03-22 15:00:50 +00:00
committed by Greg Kroah-Hartman
parent b51aa5a05a
commit 628280f36e
2 changed files with 7 additions and 0 deletions
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1
drivers/gpu/drm/i915/i915_reg.h
View File

@@ -2274,6 +2274,7 @@
#define PIPECONF_DISABLE 0
#define PIPECONF_DOUBLE_WIDE (1<<30)
#define I965_PIPECONF_ACTIVE (1<<30)
#define PIPECONF_FRAME_START_DELAY_MASK (3<<27)
#define PIPECONF_SINGLE_WIDE 0
#define PIPECONF_PIPE_UNLOCKED 0
#define PIPECONF_PIPE_LOCKED (1<<25)

6
drivers/gpu/drm/i915/intel_display.c
View File

@@ -6580,6 +6580,12 @@ 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);
I915_WRITE(reg, I915_READ(reg) & ~PIPECONF_FRAME_START_DELAY_MASK);
}
if (HAS_PCH_SPLIT(dev))
return;