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drm/i915/dp: Be paranoid in case we disable a DP before it is attached 

Given that the hardware may be left in a random condition by the BIOS,
it is conceivable that we then attempt to clear the DP_PIPEB_SELECT bit
without us ever enabling/attaching the DP encoder to a pipe. Thus
causing a NULL deference when we attempt to wait for a vblank on that
crtc.

Reported-and-tested-by: Bryan Christ <bryan.christ@gmail.com>
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=36314
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=36456
Reported-and-tested-by: Bo Wang <bo.b.wang@intel.com>
Cc: stable@kernel.org
Signed-off-by: Keith Packard <keithp@keithp.com>
This commit is contained in:
Chris Wilson 2011-04-17 06:38:35 +01:00 committed by Keith Packard
parent 2dd251f0a2
commit 31acbcc408
1 changed files with 15 additions and 2 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

17
drivers/gpu/drm/i915/intel_dp.c
View File

@ -1470,7 +1470,8 @@ intel_dp_link_down(struct intel_dp *intel_dp)
if (!HAS_PCH_CPT(dev) &&
I915_READ(intel_dp->output_reg) & DP_PIPEB_SELECT) {
struct intel_crtc *intel_crtc = to_intel_crtc(intel_dp->base.base.crtc);
struct drm_crtc *crtc = intel_dp->base.base.crtc;
/* Hardware workaround: leaving our transcoder select
* set to transcoder B while it's off will prevent the
* corresponding HDMI output on transcoder A.
@ -1485,7 +1486,19 @@ intel_dp_link_down(struct intel_dp *intel_dp)
/* Changes to enable or select take place the vblank
* after being written.
*/
intel_wait_for_vblank(dev, intel_crtc->pipe);
if (crtc == NULL) {
/* We can arrive here never having been attached
* to a CRTC, for instance, due to inheriting
* random state from the BIOS.
*
* If the pipe is not running, play safe and
* wait for the clocks to stabilise before
* continuing.
*/
POSTING_READ(intel_dp->output_reg);
msleep(50);
} else
intel_wait_for_vblank(dev, to_intel_crtc(crtc)->pipe);
}
I915_WRITE(intel_dp->output_reg, DP & ~DP_PORT_EN);