drm/i915: Disable trickle feed via MI_ARB_STATE for the gen4

According to BSpec, trickle feed should be disabled for BW and
mobile CL. Those constraints seem to match all of our gen4 chipsets.

Trickle feed is disabled via the MI_ARB_STATE register instead of
per plane controls on gen4.

Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
index 47f3c48cd3c22ee27e23f06745fba9c9a00eee33..2948764d7e3821cf348d9e7dd845ba5169cfd93d 100644 (file)
--- a/drivers/gpu/drm/i915/intel_pm.c
+++ b/drivers/gpu/drm/i915/intel_pm.c
@@ -4944,6 +4944,8 @@ static void crestline_init_clock_gating(struct drm_device *dev)
        I915_WRITE(DSPCLK_GATE_D, 0);
        I915_WRITE(RAMCLK_GATE_D, 0);
        I915_WRITE16(DEUC, 0);
+       I915_WRITE(MI_ARB_STATE,
+                  _MASKED_BIT_ENABLE(MI_ARB_DISPLAY_TRICKLE_FEED_DISABLE));
 }
 
 static void broadwater_init_clock_gating(struct drm_device *dev)
@@ -4956,6 +4958,8 @@ static void broadwater_init_clock_gating(struct drm_device *dev)
                   I965_ISC_CLOCK_GATE_DISABLE |
                   I965_FBC_CLOCK_GATE_DISABLE);
        I915_WRITE(RENCLK_GATE_D2, 0);
+       I915_WRITE(MI_ARB_STATE,
+                  _MASKED_BIT_ENABLE(MI_ARB_DISPLAY_TRICKLE_FEED_DISABLE));
 }
 
 static void gen3_init_clock_gating(struct drm_device *dev)