drm/i915/skl: Implement WaDisableVFUnitClockGating

Signed-off-by: Damien Lespiau <damien.lespiau@intel.com>
Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/i915_reg.h

@@ -6102,6 +6102,7 @@ enum skl_disp_power_wells {
 # define GEN6_CSUNIT_CLOCK_GATE_DISABLE			(1 << 7)
 
 #define GEN6_UCGCTL2				0x9404
+# define GEN6_VFUNIT_CLOCK_GATE_DISABLE			(1 << 31)
 # define GEN7_VDSUNIT_CLOCK_GATE_DISABLE		(1 << 30)
 # define GEN7_TDLUNIT_CLOCK_GATE_DISABLE		(1 << 22)
 # define GEN6_RCZUNIT_CLOCK_GATE_DISABLE		(1 << 13)

drivers/gpu/drm/i915/intel_pm.c

@@ -75,6 +75,10 @@ static void skl_init_clock_gating(struct drm_device *dev)
 		I915_WRITE(GEN8_UCGCTL6, I915_READ(GEN8_UCGCTL6) |
 			   GEN8_GAPSUNIT_CLOCK_GATE_DISABLE |
 			   GEN8_SDEUNIT_CLOCK_GATE_DISABLE);
+
+		/* WaDisableVFUnitClockGating:skl */
+		I915_WRITE(GEN6_UCGCTL2, I915_READ(GEN6_UCGCTL2) |
+			   GEN6_VFUNIT_CLOCK_GATE_DISABLE);
 	}
 
 	if (INTEL_REVID(dev) <= SKL_REVID_D0) {