diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
index 5f99d4d6291b..68a58cce6ab1 100644
--- a/drivers/gpu/drm/i915/i915_reg.h
+++ b/drivers/gpu/drm/i915/i915_reg.h
@@ -7041,6 +7041,7 @@ 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 9a4c4abc7450..a47a9c6bea52 100644
--- a/drivers/gpu/drm/i915/intel_engine_cs.c
+++ b/drivers/gpu/drm/i915/intel_engine_cs.c
@@ -1253,9 +1253,12 @@ 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 ac4cf98030f9..c42a65a93b3a 100644
--- a/drivers/gpu/drm/i915/intel_pm.c
+++ b/drivers/gpu/drm/i915/intel_pm.c
@@ -8484,14 +8484,17 @@ 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.