drm/i915/icl: Enable Sampler DFR

Sampler Dynamic Frequency Rebalancing (DFR) aims to reduce Sampler
power by dynamically changing its clock frequency in low-throughput
conditions. This patches enables it by default on Gen11.

v2: Wrong operation to clear the bit (Praveen)
v3: Rebased on top of the WA refactoring
v4: Move to icl_init_clock_gating, since it's not a WA (Rodrigo)
v5: C, not lisp (Chris)

Signed-off-by: Oscar Mateo <oscar.mateo@intel.com>
Cc: Praveen Paneri <praveen.paneri@intel.com>
Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Reviewed-by: Sagar Arun Kamble <sagar.a.kamble@intel.com>
Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Signed-off-by: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/1525814984-20039-3-git-send-email-oscar.mateo@intel.com

drivers/gpu/drm/i915/i915_reg.h

@@ -8253,6 +8253,9 @@ enum {
 #define GEN8_GARBCNTL                   _MMIO(0xB004)
 #define   GEN9_GAPS_TSV_CREDIT_DISABLE  (1<<7)
 
+#define GEN10_DFR_RATIO_EN_AND_CHICKEN	_MMIO(0x9550)
+#define   DFR_DISABLE			(1 << 9)
+
 /* IVYBRIDGE DPF */
 #define GEN7_L3CDERRST1(slice)		_MMIO(0xB008 + (slice) * 0x200) /* L3CD Error Status 1 */
 #define   GEN7_L3CDERRST1_ROW_MASK	(0x7ff<<14)

drivers/gpu/drm/i915/intel_pm.c

@@ -8664,6 +8664,13 @@ static void gen8_set_l3sqc_credits(struct drm_i915_private *dev_priv,
 	I915_WRITE(GEN7_MISCCPCTL, misccpctl);
 }
 
+static void icl_init_clock_gating(struct drm_i915_private *dev_priv)
+{
+	/* This is not an Wa. Enable to reduce Sampler power */
+	I915_WRITE(GEN10_DFR_RATIO_EN_AND_CHICKEN,
+		   I915_READ(GEN10_DFR_RATIO_EN_AND_CHICKEN) & ~DFR_DISABLE);
+}
+
 static void cnp_init_clock_gating(struct drm_i915_private *dev_priv)
 {
 	if (!HAS_PCH_CNP(dev_priv))
@@ -9191,7 +9198,7 @@ static void nop_init_clock_gating(struct drm_i915_private *dev_priv)
 void intel_init_clock_gating_hooks(struct drm_i915_private *dev_priv)
 {
 	if (IS_ICELAKE(dev_priv))
-		dev_priv->display.init_clock_gating = nop_init_clock_gating;
+		dev_priv->display.init_clock_gating = icl_init_clock_gating;
 	else if (IS_CANNONLAKE(dev_priv))
 		dev_priv->display.init_clock_gating = cnl_init_clock_gating;
 	else if (IS_COFFEELAKE(dev_priv))