drm/i915/mtl: Add Wa_22015279794

Wa_22015279794 applies to MTL P from stepping A0 to B0 (exclusive).
Signed-off-by: Radhakrishna Sripada <radhakrishna.sripada@intel.com>
Signed-off-by: Gustavo Sousa <gustavo.sousa@intel.com>
Reviewed-by: Matt Roper <matthew.d.roper@intel.com>
Signed-off-by: Matt Roper <matthew.d.roper@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230329212336.106161-3-gustavo.sousa@intel.com

drivers/gpu/drm/i915/gt/intel_gt_regs.h

@@ -1158,7 +1158,13 @@
 #define   ENABLE_EU_COUNT_FOR_TDL_FLUSH		REG_BIT(10)
 #define   DISABLE_ECC				REG_BIT(5)
 #define   FLOAT_BLEND_OPTIMIZATION_ENABLE	REG_BIT(4)
+/*
+ * We have both ENABLE and DISABLE defines below using the same bit because the
+ * meaning depends on the target platform. There are no platform prefix for them
+ * because different steppings of DG2 pick one or the other semantics.
+ */
 #define   ENABLE_PREFETCH_INTO_IC		REG_BIT(3)
+#define   DISABLE_PREFETCH_INTO_IC		REG_BIT(3)
 
 #define EU_PERF_CNTL0				PERF_REG(0xe458)
 #define EU_PERF_CNTL4				PERF_REG(0xe45c)

drivers/gpu/drm/i915/gt/intel_workarounds.c

@@ -3060,6 +3060,11 @@ general_render_compute_wa_init(struct intel_engine_cs *engine, struct i915_wa_li
 		wa_mcr_masked_en(wal, GEN10_SAMPLER_MODE,
 				 MTL_DISABLE_SAMPLER_SC_OOO);
 
+	if (IS_MTL_GRAPHICS_STEP(i915, P, STEP_A0, STEP_B0))
+		/* Wa_22015279794 */
+		wa_mcr_masked_en(wal, GEN10_CACHE_MODE_SS,
+				 DISABLE_PREFETCH_INTO_IC);
+
 	if (IS_MTL_GRAPHICS_STEP(i915, M, STEP_A0, STEP_B0) ||
 	    IS_MTL_GRAPHICS_STEP(i915, P, STEP_A0, STEP_B0) ||
 	    IS_DG2_GRAPHICS_STEP(i915, G10, STEP_B0, STEP_FOREVER) ||