drm/i915: handle FBC and self-refresh better

On 945, we need to avoid entering self-refresh if the compressor is
busy, or we may cause display FIFO underruns leading to ugly flicker.

Fixes fdo bug #24314, kernel bug #15043.

Tested-by: Alexander Lam <lambchop468@gmail.com>
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>
Tested-by: Julien Cristau <jcristau@debian.org> (fd.o #25371)
Cc: stable@kernel.org
Signed-off-by: Eric Anholt <eric@anholt.net>

diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
index 847006c..ab1bd2d 100644 (file)
--- a/drivers/gpu/drm/i915/i915_reg.h
+++ b/drivers/gpu/drm/i915/i915_reg.h
@@ -338,6 +338,7 @@
 #define   FBC_CTL_PERIODIC     (1<<30)
 #define   FBC_CTL_INTERVAL_SHIFT (16)
 #define   FBC_CTL_UNCOMPRESSIBLE (1<<14)
+#define   FBC_C3_IDLE          (1<<13)
 #define   FBC_CTL_STRIDE_SHIFT (5)
 #define   FBC_CTL_FENCENO      (1<<0)
 #define FBC_COMMAND            0x0320c

diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index 7e9c835..a4d382c 100644 (file)
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -1031,6 +1031,8 @@ static void i8xx_enable_fbc(struct drm_crtc *crtc, unsigned long interval)
 
        /* enable it... */
        fbc_ctl = FBC_CTL_EN | FBC_CTL_PERIODIC;
+       if (IS_I945GM(dev))
+               fbc_ctl |= FBC_C3_IDLE; /* 945 needs special SR handling */
        fbc_ctl |= (dev_priv->cfb_pitch & 0xff) << FBC_CTL_STRIDE_SHIFT;
        fbc_ctl |= (interval & 0x2fff) << FBC_CTL_INTERVAL_SHIFT;
        if (obj_priv->tiling_mode != I915_TILING_NONE)