[Intel-gfx] [PATCH] drm/i915: set persistent mode for fbc

[Ben Widawsky]

This seems to fix my bugs with sna enabled.

We should collect some power numbers, and validate it works on ILK
before upstreaming. (And read more about what it actually does).

Signed-off-by: Ben Widawsky <ben at bwidawsk.net>
---
 drivers/gpu/drm/i915/intel_display.c |    2 ++
 1 files changed, 2 insertions(+), 0 deletions(-)

diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index 804ac4d..4b94d71 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -1607,6 +1607,8 @@ static void ironlake_enable_fbc(struct drm_crtc *crtc, unsigned long interval)
 		I915_WRITE(SNB_DPFC_CTL_SA,
 			   SNB_CPU_FENCE_ENABLE | dev_priv->cfb_fence);
 		I915_WRITE(DPFC_CPU_FENCE_OFFSET, crtc->y);
+		/* Set persistent mode */
+		I915_WRITE(ILK_DPFC_CONTROL, 1 << 25);
 		sandybridge_blit_fbc_update(dev);
 	}
 
-- 
1.7.6