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>
diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
index 6ae8e4d..4f7a2a5 100644
--- a/drivers/gpu/drm/i915/intel_pm.c
+++ b/drivers/gpu/drm/i915/intel_pm.c
@@ -3891,6 +3891,7 @@
 	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 @@
 	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 @@
 				   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);
 
 }