drm/i915: Set persistent-mode for ILK/SNB framebuffer compression
Persistent mode is intended for use with front-buffer rendering, such as
X, where it is necessary to detect writes to the scanout either by the
GPU or through the CPU's fence, and recompress the dirty regions on the
fly. (By comparison to the back-buffer rendering, the scanout is always
recompressed after a page-flip.)
References: https://bugs.freedesktop.org/show_bug.cgi?id=33487
References: https://bugs.freedesktop.org/show_bug.cgi?id=31742
Signed-off-by: Ben Widawsky <ben@bwidawsk.net>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Jesse Barnes <jbarnes@virtuousgeek.org>
Signed-off-by: Keith Packard <keithp@keithp.com>
diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index 31c7526..9df96bd 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -1581,6 +1581,8 @@
dpfc_ctl &= DPFC_RESERVED;
dpfc_ctl |= (plane | DPFC_CTL_LIMIT_1X);
+ /* Set persistent mode for front-buffer rendering, ala X. */
+ dpfc_ctl |= DPFC_CTL_PERSISTENT_MODE;
dpfc_ctl |= (DPFC_CTL_FENCE_EN | dev_priv->cfb_fence);
I915_WRITE(ILK_DPFC_CHICKEN, DPFC_HT_MODIFY);