drm/i915:skl: Add WaEnableGapsTsvCreditFix

Cc: Ben Widawsky <benjamin.widawsky@intel.com>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Signed-off-by: Arun Siluvery <arun.siluvery@linux.intel.com>
Tested-by: Ben Widawsky <ben@bwidawsk.net>
Reviewed-by: Ben Widawsky <ben@bwidawsk.net>
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=90854
Tested-by: Mika Kuoppala <mika.kuoppala@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/i915_reg.h

@@ -6851,6 +6851,9 @@ enum skl_disp_power_wells {
 #define GEN7_MISCCPCTL			(0x9424)
 #define   GEN7_DOP_CLOCK_GATE_ENABLE	(1<<0)
 
+#define GEN8_GARBCNTL                   0xB004
+#define   GEN9_GAPS_TSV_CREDIT_DISABLE  (1<<7)
+
 /* IVYBRIDGE DPF */
 #define GEN7_L3CDERRST1			0xB008 /* L3CD Error Status 1 */
 #define HSW_L3CDERRST11			0xB208 /* L3CD Error Status register 1 slice 1 */

drivers/gpu/drm/i915/intel_pm.c

@@ -102,6 +102,12 @@ static void skl_init_clock_gating(struct drm_device *dev)
 		/* WaDisableLSQCROPERFforOCL:skl */
 		I915_WRITE(GEN8_L3SQCREG4, I915_READ(GEN8_L3SQCREG4) |
 			   GEN8_LQSC_RO_PERF_DIS);
+
+	/* WaEnableGapsTsvCreditFix:skl */
+	if (IS_SKYLAKE(dev) && (INTEL_REVID(dev) >= SKL_REVID_C0)) {
+		I915_WRITE(GEN8_GARBCNTL, (I915_READ(GEN8_GARBCNTL) |
+					   GEN9_GAPS_TSV_CREDIT_DISABLE));
+	}
 }
 
 static void bxt_init_clock_gating(struct drm_device *dev)