According to bspec we need to disable gam unit clock gating on
on kbl revids A0 and B0.

References: HSD#2226858, HSD#1944358
Signed-off-by: Mika Kuoppala <mika.kuopp...@intel.com>
---
 drivers/gpu/drm/i915/i915_reg.h | 1 +
 drivers/gpu/drm/i915/intel_pm.c | 5 +++++
 2 files changed, 6 insertions(+)

diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
index 5cba851370ec..14e0ec818ea4 100644
--- a/drivers/gpu/drm/i915/i915_reg.h
+++ b/drivers/gpu/drm/i915/i915_reg.h
@@ -6937,6 +6937,7 @@ enum skl_disp_power_wells {
 #define    EDRAM_SETS_IDX(cap)                 (((cap) >> 8) & 0x3)
 
 #define GEN6_UCGCTL1                           _MMIO(0x9400)
+# define GEN6_GAMUNIT_CLOCK_GATE_DISABLE               (1 << 22)
 # define GEN6_EU_TCUNIT_CLOCK_GATE_DISABLE             (1 << 16)
 # define GEN6_BLBUNIT_CLOCK_GATE_DISABLE               (1 << 5)
 # define GEN6_CSUNIT_CLOCK_GATE_DISABLE                        (1 << 7)
diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
index b40f9dbbb215..8291f32db76e 100644
--- a/drivers/gpu/drm/i915/intel_pm.c
+++ b/drivers/gpu/drm/i915/intel_pm.c
@@ -6869,6 +6869,11 @@ static void kabylake_init_clock_gating(struct drm_device 
*dev)
        if (IS_KBL_REVID(dev_priv, 0, KBL_REVID_B0))
                I915_WRITE(GEN8_UCGCTL6, I915_READ(GEN8_UCGCTL6) |
                           GEN8_SDEUNIT_CLOCK_GATE_DISABLE);
+
+       /* WaDisableGamClockGating:kbl */
+       if (IS_KBL_REVID(dev_priv, 0, KBL_REVID_B0))
+               I915_WRITE(GEN6_UCGCTL1, I915_READ(GEN6_UCGCTL1) |
+                          GEN6_GAMUNIT_CLOCK_GATE_DISABLE);
 }
 
 static void skylake_init_clock_gating(struct drm_device *dev)
-- 
2.5.0

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