drm/i915/pvc: Implement recommended caching policy

As per the performance tuning guide, set the HOSTCACHEEN bit to
implement the recommended caching policy on PVC.
Signed-off-by: Wayne Boyer <wayne.boyer@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/20221130170723.2460014-1-wayne.boyer@intel.com

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

@@ -972,6 +972,7 @@
 #define   GEN7_L3AGDIS				(1 << 19)
 
 #define XEHPC_LNCFMISCCFGREG0			_MMIO(0xb01c)
+#define   XEHPC_HOSTCACHEEN			REG_BIT(1)
 #define   XEHPC_OVRLSCCC			REG_BIT(0)
 
 #define GEN7_L3CNTLREG2				_MMIO(0xb020)

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

@@ -2906,6 +2906,7 @@ add_render_compute_tuning_settings(struct drm_i915_private *i915,
 	if (IS_PONTEVECCHIO(i915)) {
 		wa_write(wal, XEHPC_L3SCRUB,
 			 SCRUB_CL_DWNGRADE_SHARED | SCRUB_RATE_4B_PER_CLK);
+		wa_masked_en(wal, XEHPC_LNCFMISCCFGREG0, XEHPC_HOSTCACHEEN);
 	}
 
 	if (IS_DG2(i915)) {