drm/i915/icl:Add Wa_1606682166

Incorrect TDL's SSP address shift in SARB for 16:6 & 18:8 modes.
Disable the Sampler state prefetch functionality in the SARB by
programming 0xB000[30] to '1'. This is to be done at boot time
and the feature must remain disabled permanently.

Fixes flaky tex-mip-level-selection* piglit tests with Mesa i965
driver.

Cc: Radhakrishna Sripada <radhakrishna.sripada@intel.com>
Signed-off-by: Anuj Phogat <anuj.phogat@gmail.com>
Reviewed-by: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Signed-off-by: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20181004182939.7668-6-radhakrishna.sripada@intel.com

drivers/gpu/drm/i915/i915_reg.h

@@ -7414,6 +7414,7 @@ enum {
 
 #define GEN7_SARCHKMD				_MMIO(0xB000)
 #define GEN7_DISABLE_DEMAND_PREFETCH		(1 << 31)
+#define GEN7_DISABLE_SAMPLER_PREFETCH           (1 << 30)
 
 #define GEN7_L3SQCREG1				_MMIO(0xB010)
 #define  VLV_B0_WA_L3SQCREG1_VALUE		0x00D30000

drivers/gpu/drm/i915/intel_workarounds.c

@@ -910,7 +910,8 @@ static void icl_gt_workarounds_apply(struct drm_i915_private *dev_priv)
 	if (IS_ICL_REVID(dev_priv, ICL_REVID_A0, ICL_REVID_B0))
 		I915_WRITE(GEN7_SARCHKMD,
 			   I915_READ(GEN7_SARCHKMD) |
-			   GEN7_DISABLE_DEMAND_PREFETCH);
+			   GEN7_DISABLE_DEMAND_PREFETCH |
+			   GEN7_DISABLE_SAMPLER_PREFETCH);
 }
 
 void intel_gt_workarounds_apply(struct drm_i915_private *dev_priv)