drm/i915/crt: Flush register prior to waiting for vblank.
If we don't flush the write then we can not be sure that the border
colour will have taken effect by the time we try to read it back.
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
diff --git a/drivers/gpu/drm/i915/intel_crt.c b/drivers/gpu/drm/i915/intel_crt.c
index c2982e4..6262797 100644
--- a/drivers/gpu/drm/i915/intel_crt.c
+++ b/drivers/gpu/drm/i915/intel_crt.c
@@ -327,6 +327,7 @@
if (IS_I9XX(dev)) {
uint32_t pipeconf = I915_READ(pipeconf_reg);
I915_WRITE(pipeconf_reg, pipeconf | PIPECONF_FORCE_BORDER);
+ POSTING_READ(pipeconf_reg);
/* Wait for next Vblank to substitue
* border color for Color info */
intel_wait_for_vblank(dev, pipe);