drm/i915: enable trickle feed on Haswell

We shouldn't disable the trickle feed bits on Haswell. Our
documentation explicitly says the trickle feed bits of PRI_CTL and
CUR_CTL should not be programmed to 1, and the hardware engineer also
asked us to not program the SPR_CTL field to 1. Leaving the bits as 1
could cause underflows.

Reported-by: Arthur Runyan <arthur.j.runyan@intel.com>
Signed-off-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/i915_reg.h

@@ -3313,6 +3313,7 @@
 #define   MCURSOR_PIPE_A	0x00
 #define   MCURSOR_PIPE_B	(1 << 28)
 #define   MCURSOR_GAMMA_ENABLE  (1 << 26)
+#define   CURSOR_TRICKLE_FEED_DISABLE	(1 << 14)
 #define _CURABASE		(dev_priv->info->display_mmio_offset + 0x70084)
 #define _CURAPOS		(dev_priv->info->display_mmio_offset + 0x70088)
 #define   CURSOR_POS_MASK       0x007FF

drivers/gpu/drm/i915/intel_display.c

@@ -2077,8 +2077,10 @@ static int ironlake_update_plane(struct drm_crtc *crtc,
 	else
 		dspcntr &= ~DISPPLANE_TILED;
 
-	/* must disable */
-	dspcntr |= DISPPLANE_TRICKLE_FEED_DISABLE;
+	if (IS_HASWELL(dev))
+		dspcntr &= ~DISPPLANE_TRICKLE_FEED_DISABLE;
+	else
+		dspcntr |= DISPPLANE_TRICKLE_FEED_DISABLE;
 
 	I915_WRITE(reg, dspcntr);
 
@@ -6762,8 +6764,10 @@ static void ivb_update_cursor(struct drm_crtc *crtc, u32 base)
 			cntl &= ~(CURSOR_MODE | MCURSOR_GAMMA_ENABLE);
 			cntl |= CURSOR_MODE_DISABLE;
 		}
-		if (IS_HASWELL(dev))
+		if (IS_HASWELL(dev)) {
 			cntl |= CURSOR_PIPE_CSC_ENABLE;
+			cntl &= ~CURSOR_TRICKLE_FEED_DISABLE;
+		}
 		I915_WRITE(CURCNTR_IVB(pipe), cntl);
 
 		intel_crtc->cursor_visible = visible;

drivers/gpu/drm/i915/intel_pm.c

@@ -4960,8 +4960,6 @@ static void haswell_init_clock_gating(struct drm_device *dev)
 			I915_READ(GEN7_SQ_CHICKEN_MBCUNIT_CONFIG) |
 			GEN7_SQ_CHICKEN_MBCUNIT_SQINTMOB);
 
-	g4x_disable_trickle_feed(dev);
-
 	/* WaVSRefCountFullforceMissDisable:hsw */
 	gen7_setup_fixed_func_scheduler(dev_priv);
 

drivers/gpu/drm/i915/intel_sprite.c

@@ -260,8 +260,11 @@ ivb_update_plane(struct drm_plane *plane, struct drm_crtc *crtc,
 	if (obj->tiling_mode != I915_TILING_NONE)
 		sprctl |= SPRITE_TILED;
 
-	/* must disable */
-	sprctl |= SPRITE_TRICKLE_FEED_DISABLE;
+	if (IS_HASWELL(dev))
+		sprctl &= ~SPRITE_TRICKLE_FEED_DISABLE;
+	else
+		sprctl |= SPRITE_TRICKLE_FEED_DISABLE;
+
 	sprctl |= SPRITE_ENABLE;
 
 	if (IS_HASWELL(dev))