Workaround requires programing L3 tag clock timing register.
Signed-off-by: Michel Thierry <michel.thierry@xxxxxxxxx>
---
drivers/gpu/drm/i915/i915_reg.h | 4 ++++
drivers/gpu/drm/i915/intel_pm.c | 9 +++++++++
2 files changed, 13 insertions(+)
diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
index 55ea3bf..ff1acbe 100644
--- a/drivers/gpu/drm/i915/i915_reg.h
+++ b/drivers/gpu/drm/i915/i915_reg.h
@@ -4709,6 +4709,10 @@ enum punit_power_well {
#define GEN8_L3SQCREG1 0xb100
#define GEN8_L3SQCREG1_DEFAULT_VALUE 0x784000
+#define GEN8_L3CNTLREG1 0xb10c
+#define GEN8_TAG_CLK_OFFTIME (1<<23)
+#define GEN8_TAG_CLK_OFFTIME_MASK (~((1<<23) | (1<<22) | (1<<21) | (1<<20)))
+
#define GEN8_L3SQCREG4 0xb118
#define GEN8_PIPELINE_FLUSH_COHERENT_LINES (1<<21)
diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
index b60fbd2..64e3245 100644
--- a/drivers/gpu/drm/i915/intel_pm.c
+++ b/drivers/gpu/drm/i915/intel_pm.c
@@ -5496,6 +5496,15 @@ static void gen8_init_clock_gating(struct drm_device *dev)
/* WaFlushCoherentL3CacheLinesAtContextSwitch:bdw */
I915_WRITE(GEN8_L3SQCREG4, I915_READ(GEN8_L3SQCREG4) |
GEN8_PIPELINE_FLUSH_COHERENT_LINES);
+
+ /*
+ * WaIncreaseTagClockTimer:bdw
+ * This register is not masked and the default value is not all zero.
+ * Use the mask with and to clear out bits 23:20.
+ */
+ I915_WRITE(GEN8_L3CNTLREG1, (I915_READ(GEN8_L3CNTLREG1) &
+ GEN8_TAG_CLK_OFFTIME_MASK) |
+ GEN8_TAG_CLK_OFFTIME);
}
static void haswell_init_clock_gating(struct drm_device *dev)
--
1.9.0
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