drm/i915/cnl: WaRsUseTimeoutMode

Apparently RC6 residency is lower than expected
with EI mode for most of the cases on CNL A0, B0 and C0.

This Wa doesn't solve our lower residency, but I
believe it is better to have it since EI is not
expected to work by HW engineers anyways.

Cc: David Weinehall <david.weinehall@linux.intel.com>
Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Reviewed-by: David Weinehall <david.weinehall@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20170822235828.18322-1-rodrigo.vivi@intel.com

drivers/gpu/drm/i915/i915_drv.h

@@ -3077,6 +3077,7 @@ intel_info(const struct drm_i915_private *dev_priv)
 
 #define CNL_REVID_A0		0x0
 #define CNL_REVID_B0		0x1
+#define CNL_REVID_C0		0x2
 
 #define IS_CNL_REVID(p, since, until) \
 	(IS_CANNONLAKE(p) && IS_REVID(p, since, until))

drivers/gpu/drm/i915/intel_pm.c

@@ -6591,7 +6591,7 @@ static void gen9_enable_rc6(struct drm_i915_private *dev_priv)
 {
 	struct intel_engine_cs *engine;
 	enum intel_engine_id id;
-	uint32_t rc6_mask = 0;
+	u32 rc6_mode, rc6_mask = 0;
 
 	/* 1a: Software RC state - RC0 */
 	I915_WRITE(GEN6_RC_STATE, 0);
@@ -6629,8 +6629,15 @@ static void gen9_enable_rc6(struct drm_i915_private *dev_priv)
 		rc6_mask = GEN6_RC_CTL_RC6_ENABLE;
 	DRM_INFO("RC6 %s\n", onoff(rc6_mask & GEN6_RC_CTL_RC6_ENABLE));
 	I915_WRITE(GEN6_RC6_THRESHOLD, 37500); /* 37.5/125ms per EI */
+
+	/* WaRsUseTimeoutMode:cnl (pre-prod) */
+	if (IS_CNL_REVID(dev_priv, CNL_REVID_A0, CNL_REVID_C0))
+		rc6_mode = GEN7_RC_CTL_TO_MODE;
+	else
+		rc6_mode = GEN6_RC_CTL_EI_MODE(1);
+
 	I915_WRITE(GEN6_RC_CONTROL,
-		   GEN6_RC_CTL_HW_ENABLE | GEN6_RC_CTL_EI_MODE(1) | rc6_mask);
+		   GEN6_RC_CTL_HW_ENABLE | rc6_mode | rc6_mask);
 
 	/*
 	 * 3b: Enable Coarse Power Gating only when RC6 is enabled.