drm/i915: Disable tesselation clock gating on tgl A0

Disable TEDOP clock gating flow by programming 0x20A0[19] = 1

References: HSDES#1407928979
Signed-off-by: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Link: https://patchwork.freedesktop.org/patch/msgid/20200207155138.30978-1-mika.kuoppala@linux.intel.com

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

@@ -1352,6 +1352,11 @@ rcs_engine_wa_init(struct intel_engine_cs *engine, struct i915_wa_list *wal)
 		wa_write_or(wal,
 			    GEN7_SARCHKMD,
 			    GEN7_DISABLE_SAMPLER_PREFETCH);
+
+		/* Wa_1407928979:tgl */
+		wa_write_or(wal,
+			    GEN7_FF_THREAD_MODE,
+			    GEN12_FF_TESSELATION_DOP_GATE_DISABLE);
 	}
 
 	if (IS_GEN(i915, 11)) {

drivers/gpu/drm/i915/i915_reg.h

@@ -3165,6 +3165,7 @@ static inline bool i915_mmio_reg_valid(i915_reg_t reg)
 #define GEN7_FF_THREAD_MODE		_MMIO(0x20a0)
 #define   GEN7_FF_SCHED_MASK		0x0077070
 #define   GEN8_FF_DS_REF_CNT_FFME	(1 << 19)
+#define   GEN12_FF_TESSELATION_DOP_GATE_DISABLE BIT(19)
 #define   GEN7_FF_TS_SCHED_HS1		(0x5 << 16)
 #define   GEN7_FF_TS_SCHED_HS0		(0x3 << 16)
 #define   GEN7_FF_TS_SCHED_LOAD_BALANCE	(0x1 << 16)