linux-kernel - [PATCH] i915/fbc: Disable on HSW by default for now

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Date:	Thu,  9 Jun 2016 11:58:15 -0400
From:	Lyude <cpaul@...hat.com>
To:	intel-gfx@...ts.freedesktop.org,
	Paulo Zanoni <paulo.r.zanoni@...el.com>,
	Rob Clark <rclark@...hat.com>
Cc:	Lyude <cpaul@...hat.com>, stable@...r.kernel.org,
	Daniel Vetter <daniel.vetter@...el.com>,
	Jani Nikula <jani.nikula@...ux.intel.com>,
	David Airlie <airlied@...ux.ie>,
	dri-devel@...ts.freedesktop.org (open list:INTEL DRM DRIVERS (excluding
	Poulsbo, Moorestow...), linux-kernel@...r.kernel.org (open list))
Subject: [PATCH] i915/fbc: Disable on HSW by default for now

>From https://bugs.freedesktop.org/show_bug.cgi?id=96461 :

This was kind of a difficult bug to track down. If you're using a
Haswell system running GNOME and you have fbc completely enabled and
working, playing videos can result in video artifacts. Steps to
reproduce:

- Run GNOME
- Ensure FBC is enabled and active
- Download a movie, I used the ogg version of Big Buck Bunny for this
- Run `gst-launch-1.0 filesrc location='some_movie.ogg' ! decodebin !
  glimagesink` in a terminal
- Watch for about over a minute, you'll see small horizontal lines go
  down the screen.

For the time being, disable FBC for Haswell by default.

Signed-off-by: Lyude <cpaul@...hat.com>
Cc: stable@...r.kernel.org
---
 drivers/gpu/drm/i915/intel_fbc.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/i915/intel_fbc.c b/drivers/gpu/drm/i915/intel_fbc.c
index 0f0492f..28f4407 100644
--- a/drivers/gpu/drm/i915/intel_fbc.c
+++ b/drivers/gpu/drm/i915/intel_fbc.c
@@ -823,8 +823,7 @@ static bool intel_fbc_can_choose(struct intel_crtc *crtc)
 {
 	struct drm_i915_private *dev_priv = crtc->base.dev->dev_private;
 	struct intel_fbc *fbc = &dev_priv->fbc;
-	bool enable_by_default = IS_HASWELL(dev_priv) ||
-				 IS_BROADWELL(dev_priv);
+	bool enable_by_default = IS_BROADWELL(dev_priv);
 
 	if (intel_vgpu_active(dev_priv->dev)) {
 		fbc->no_fbc_reason = "VGPU is active";
-- 
2.5.5