drm/i915/gen9: WA ST Unit Power Optimization Disable

WaDisableSTUnitPowerOptimization:skl,bxt
Signed-off-by: Robert Beckett <robert.beckett@intel.com>
Signed-off-by: Arun Siluvery <arun.siluvery@linux.intel.com>
Reviewed-by: Sagar Arun Kamble <sagar.a.kamble@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/i915_reg.h

@@ -6943,6 +6943,9 @@ enum skl_disp_power_wells {
 #define HSW_ROW_CHICKEN3		0xe49c
 #define  HSW_ROW_CHICKEN3_L3_GLOBAL_ATOMICS_DISABLE    (1 << 6)
 
+#define HALF_SLICE_CHICKEN2		0xe180
+#define   GEN8_ST_PO_DISABLE		(1<<13)
+
 #define HALF_SLICE_CHICKEN3		0xe184
 #define   HSW_SAMPLE_C_PERFORMANCE	(1<<9)
 #define   GEN8_CENTROID_PIXEL_OPT_DIS	(1<<8)

drivers/gpu/drm/i915/intel_ringbuffer.c

@@ -990,6 +990,9 @@ static int gen9_init_workarounds(struct intel_engine_cs *ring)
 				  GEN8_SAMPLER_POWER_BYPASS_DIS);
 	}
 
+	/* WaDisableSTUnitPowerOptimization:skl,bxt */
+	WA_SET_BIT_MASKED(HALF_SLICE_CHICKEN2, GEN8_ST_PO_DISABLE);
+
 	return 0;
 }