[PATCH 4/4] drm/i915: WaFbcDisableDpfcClockGating only with fbc

[Ben Widawsky <benjamin.widawsky@intel.com>]

We were turning this on for SNB regardless of whether or not we use FBC.
We can save the slightest amount of power if we don't disable it when
not using FBC.

The workaround should be bit 9 for SNB.

Signed-off-by: Ben Widawsky <ben@bwidawsk.net>
---
 drivers/gpu/drm/i915/intel_pm.c | 25 +++++++++++++++----------
 1 file changed, 15 insertions(+), 10 deletions(-)

diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
index bbcf100..4ebbe65 100644
--- a/drivers/gpu/drm/i915/intel_pm.c
+++ b/drivers/gpu/drm/i915/intel_pm.c
@@ -237,6 +237,12 @@ static void ironlake_enable_fbc(struct drm_crtc *crtc, unsigned long interval)
 		I915_WRITE(SNB_DPFC_CTL_SA,
 			   SNB_CPU_FENCE_ENABLE | obj->fence_reg);
 		I915_WRITE(DPFC_CPU_FENCE_OFFSET, crtc->y);
+
+		/* WaFbcDisableDpfcClockGating:snb */
+		I915_WRITE(ILK_DSPCLK_GATE_D,
+			   I915_READ(ILK_DSPCLK_GATE_D) |
+			   ILK_DPFCUNIT_CLOCK_GATE_DISABLE);
+
 		sandybridge_blit_fbc_update(dev);
 	} else {
 		/* WaFbcDisableDpfcClockGating:ilk */
@@ -259,7 +265,12 @@ static void ironlake_disable_fbc(struct drm_device *dev)
 		dpfc_ctl &= ~DPFC_CTL_EN;
 		I915_WRITE(ILK_DPFC_CONTROL, dpfc_ctl);
 
-		if (IS_GEN5(dev))
+		if (IS_GEN6(dev))
+			/* WaFbcDisableDpfcClockGating:snb */
+			I915_WRITE(ILK_DSPCLK_GATE_D,
+				   I915_READ(ILK_DSPCLK_GATE_D) &
+				   ~ILK_DPFCUNIT_CLOCK_GATE_DISABLE);
+		else if (IS_GEN5(dev))
 			/* WaFbcDisableDpfcClockGating:ilk */
 			I915_WRITE(ILK_DSPCLK_GATE_D,
 				   I915_READ(ILK_DSPCLK_GATE_D) &
@@ -4939,15 +4950,9 @@ static void g4x_disable_trickle_feed(struct drm_device *dev)
 static void ironlake_init_clock_gating(struct drm_device *dev)
 {
 	struct drm_i915_private *dev_priv = dev->dev_private;
-	uint32_t dspclk_gate = ILK_VRHUNIT_CLOCK_GATE_DISABLE;
-
-	/*
-	 * Required for FBC
-	 * WaFbcDisableDpfcClockGating:snb
-	 */
-	dspclk_gate |=
-		   ILK_DPFCUNIT_CLOCK_GATE_DISABLE |
-		   ILK_DPFDUNIT_CLOCK_GATE_ENABLE;
+	uint32_t dspclk_gate =
+		ILK_VRHUNIT_CLOCK_GATE_DISABLE |
+		ILK_DPFDUNIT_CLOCK_GATE_ENABLE;
 
 	I915_WRITE(PCH_3DCGDIS0,
 		   MARIUNIT_CLOCK_GATE_DISABLE |
-- 
1.8.4.1