[PATCH 3.13 142/198] drm/i915: Disable FBC by default also on Haswell and later

From: Kamal Mostafa
Date: Tue Jul 15 2014 - 17:45:48 EST -stable review patch. If anyone has any objections, please let me know.


From: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>

commit 0368920e51ae0cded0eb518c340a4dd17764d461 upstream.

It causes black screen on bootup and is approximately 100x slower than
running with FBC disabled, so the GPU runs at a high frequency for much
longer - completely contrary to the power saving claims. It also still
has mutex deadlocks in multi-head scenarios, which can lead to a
system/X lockup. These bugs were known before FBC was enabled by default
on Haswell and still have not been fixed.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=79716
Reported-and-tested-by: Jon Kristensen <info@xxxxxxxxxx>
Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
Reviewed-by: Daniel Vetter <daniel.vetter@xxxxxxxx>
[Jani: update subject to reflect the actual change]
Signed-off-by: Jani Nikula <jani.nikula@xxxxxxxxx>
[ kamal: backport to 3.13-stable ]
Signed-off-by: Kamal Mostafa <kamal@xxxxxxxxxxxxx>
drivers/gpu/drm/i915/intel_pm.c | 3 +--
1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
index 4128d0e..1218c44 100644
--- a/drivers/gpu/drm/i915/intel_pm.c
+++ b/drivers/gpu/drm/i915/intel_pm.c
@@ -498,8 +498,7 @@ void intel_update_fbc(struct drm_device *dev)
obj = intel_fb->obj;
adjusted_mode = &intel_crtc->config.adjusted_mode;

- if (i915_enable_fbc < 0 &&
- INTEL_INFO(dev)->gen <= 7 && !IS_HASWELL(dev)) {
+ if (i915_enable_fbc < 0) {
if (set_no_fbc_reason(dev_priv, FBC_CHIP_DEFAULT))
DRM_DEBUG_KMS("disabled per chip default\n");
goto out_disable;

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