[Intel-gfx] [PATCH 1/2] drm/i915: tune the RC6 threshold for stability

[Stéphane Marchesin]

It's basically the same deal as the RC6+ issues on ivy bridge
except this time with RC6 on sandy bridge. Like last time the
core of the issue is that the timings don't work 100% with our
voltage regulator. So from time to time, the kernel will print
a warning message about the GPU not getting out of RC6. In
particular, I found this fairly easy to reproduce during
suspend/resume.

Changing the threshold to 150000 instead of 50000 seems to fix
the issue.

I also measured the idle power usage before/after this patch and
didn't see a difference on a sandy bridge laptop.

Signed-off-by: Stéphane Marchesin <marcheu at chromium.org>
---
 drivers/gpu/drm/i915/intel_pm.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
index aa01128..52fe8f7 100644
--- a/drivers/gpu/drm/i915/intel_pm.c
+++ b/drivers/gpu/drm/i915/intel_pm.c
@@ -2577,7 +2577,7 @@ static void gen6_enable_rps(struct drm_device *dev)
 
 	I915_WRITE(GEN6_RC_SLEEP, 0);
 	I915_WRITE(GEN6_RC1e_THRESHOLD, 1000);
-	I915_WRITE(GEN6_RC6_THRESHOLD, 50000);
+	I915_WRITE(GEN6_RC6_THRESHOLD, 150000);
 	I915_WRITE(GEN6_RC6p_THRESHOLD, 150000);
 	I915_WRITE(GEN6_RC6pp_THRESHOLD, 64000); /* unused */
 
-- 
1.8.3