drm/i915/skl: Gen9 coarse power gating

Enable coarse power gating for Gen9. This feature allows render and
media engine to enter RC6 independently. Policies are configured
together with RC6. This feature will only be enabled when RC6 is
enabled.

v2: Rebase after Chris'/Mika's forcewake change (Damien)
Reviewed-by: Damien Lespiau <damien.lespiau@intel.com>
Signed-off-by: Zhe Wang <zhe1.wang@intel.com>
Signed-off-by: Damien Lespiau <damien.lespiau@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/i915_reg.h

@@ -6072,6 +6072,9 @@ enum punit_power_well {
 #define GEN6_PMINTRMSK				0xA168
 #define GEN8_PMINTR_REDIRECT_TO_NON_DISP	(1<<31)
 #define VLV_PWRDWNUPCTL				0xA294
+#define GEN9_MEDIA_PG_IDLE_HYSTERESIS		0xA0C4
+#define GEN9_RENDER_PG_IDLE_HYSTERESIS		0xA0C8
+#define GEN9_PG_ENABLE				0xA210
 
 #define VLV_CHICKEN_3				(VLV_DISPLAY_BASE + 0x7040C)
 #define  PIXEL_OVERLAP_CNT_MASK			(3 << 30)

drivers/gpu/drm/i915/intel_pm.c

@@ -3891,6 +3891,7 @@ static void gen9_disable_rps(struct drm_device *dev)
 	struct drm_i915_private *dev_priv = dev->dev_private;
 
 	I915_WRITE(GEN6_RC_CONTROL, 0);
+	I915_WRITE(GEN9_PG_ENABLE, 0);
 }
 
 static void gen6_disable_rps(struct drm_device *dev)
@@ -4080,6 +4081,10 @@ static void gen9_enable_rc6(struct drm_device *dev)
 	I915_WRITE(GEN6_RC_SLEEP, 0);
 	I915_WRITE(GEN6_RC6_THRESHOLD, 37500); /* 37.5/125ms per EI */
 
+	/* 2c: Program Coarse Power Gating Policies. */
+	I915_WRITE(GEN9_MEDIA_PG_IDLE_HYSTERESIS, 25);
+	I915_WRITE(GEN9_RENDER_PG_IDLE_HYSTERESIS, 25);
+
 	/* 3a: Enable RC6 */
 	if (intel_enable_rc6(dev) & INTEL_RC6_ENABLE)
 		rc6_mask = GEN6_RC_CTL_RC6_ENABLE;
@@ -4089,6 +4094,9 @@ static void gen9_enable_rc6(struct drm_device *dev)
 				   GEN6_RC_CTL_EI_MODE(1) |
 				   rc6_mask);
 
+	/* 3b: Enable Coarse Power Gating only when RC6 is enabled */
+	I915_WRITE(GEN9_PG_ENABLE, (rc6_mask & GEN6_RC_CTL_RC6_ENABLE) ? 3 : 0);
+
 	intel_uncore_forcewake_put(dev_priv, FORCEWAKE_ALL);
 
 }