3 files changed, 13 insertions, 6 deletions

diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
index ed7cd9ee2c2a..c9bcc6c45012 100644
--- a/drivers/gpu/drm/i915/i915_reg.h
+++ b/drivers/gpu/drm/i915/i915_reg.h
@@ -6998,6 +6998,7 @@ enum {
  */
 #define  L3_GENERAL_PRIO_CREDITS(x)             (((x) >> 1) << 19)
 #define  L3_HIGH_PRIO_CREDITS(x)                (((x) >> 1) << 14)
+#define  L3_PRIO_CREDITS_MASK                   ((0x1f << 19) | (0x1f << 14))
 
 #define GEN7_L3CNTLREG1                         _MMIO(0xB01C)
 #define  GEN7_WA_FOR_GEN7_L3_CONTROL                    0x3C47FF8C
diff --git a/drivers/gpu/drm/i915/intel_engine_cs.c b/drivers/gpu/drm/i915/intel_engine_cs.c
index 9ab596941372..3c2d9cf22ed5 100644
--- a/drivers/gpu/drm/i915/intel_engine_cs.c
+++ b/drivers/gpu/drm/i915/intel_engine_cs.c
@@ -1048,9 +1048,12 @@ static int bxt_init_workarounds(struct intel_engine_cs *engine)
         }
 
         /* WaProgramL3SqcReg1DefaultForPerf:bxt */
-        if (IS_BXT_REVID(dev_priv, BXT_REVID_B0, REVID_FOREVER))
-                I915_WRITE(GEN8_L3SQCREG1, L3_GENERAL_PRIO_CREDITS(62) |
-                                           L3_HIGH_PRIO_CREDITS(2));
+        if (IS_BXT_REVID(dev_priv, BXT_REVID_B0, REVID_FOREVER)) {
+                u32 val = I915_READ(GEN8_L3SQCREG1);
+                val &= ~L3_PRIO_CREDITS_MASK;
+                val |= L3_GENERAL_PRIO_CREDITS(62) | L3_HIGH_PRIO_CREDITS(2);
+                I915_WRITE(GEN8_L3SQCREG1, val);
+        }
 
         /* WaToEnableHwFixForPushConstHWBug:bxt */
         if (IS_BXT_REVID(dev_priv, BXT_REVID_C0, REVID_FOREVER))
diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
index ed662937ec3c..0a09f8ff6aff 100644
--- a/drivers/gpu/drm/i915/intel_pm.c
+++ b/drivers/gpu/drm/i915/intel_pm.c
@@ -8245,14 +8245,17 @@ static void gen8_set_l3sqc_credits(struct drm_i915_private *dev_priv,
                                    int high_prio_credits)
 {
         u32 misccpctl;
+        u32 val;
 
         /* WaTempDisableDOPClkGating:bdw */
         misccpctl = I915_READ(GEN7_MISCCPCTL);
         I915_WRITE(GEN7_MISCCPCTL, misccpctl & ~GEN7_DOP_CLOCK_GATE_ENABLE);
 
-        I915_WRITE(GEN8_L3SQCREG1,
-                   L3_GENERAL_PRIO_CREDITS(general_prio_credits) |
-                   L3_HIGH_PRIO_CREDITS(high_prio_credits));
+        val = I915_READ(GEN8_L3SQCREG1);
+        val &= ~L3_PRIO_CREDITS_MASK;
+        val |= L3_GENERAL_PRIO_CREDITS(general_prio_credits);
+        val |= L3_HIGH_PRIO_CREDITS(high_prio_credits);
+        I915_WRITE(GEN8_L3SQCREG1, val);
 
         /*
          * Wait at least 100 clocks before re-enabling clock gating.