diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
index 20244b971fc6..c4b1a2b45bb4 100644
--- a/drivers/gpu/drm/i915/i915_reg.h
+++ b/drivers/gpu/drm/i915/i915_reg.h
@@ -1807,18 +1807,35 @@
 #define PFIT_AUTO_RATIOS 0x61238
 
 /* Backlight control */
-#define BLC_PWM_CTL		0x61254
-#define   BACKLIGHT_MODULATION_FREQ_SHIFT		(17)
 #define BLC_PWM_CTL2		0x61250 /* 965+ only */
-#define   BLM_COMBINATION_MODE (1 << 30)
+#define   BLM_PWM_ENABLE		(1 << 31)
+#define   BLM_COMBINATION_MODE		(1 << 30) /* gen4 only */
+#define   BLM_PIPE_SELECT		(1 << 29)
+#define   BLM_PIPE_SELECT_IVB		(3 << 29)
+#define   BLM_PIPE_A			(0 << 29)
+#define   BLM_PIPE_B			(1 << 29)
+#define   BLM_PIPE_C			(2 << 29) /* ivb + */
+#define   BLM_PIPE(pipe)		((pipe) << 29)
+#define   BLM_POLARITY_I965		(1 << 28) /* gen4 only */
+#define   BLM_PHASE_IN_INTERUPT_STATUS	(1 << 26)
+#define   BLM_PHASE_IN_ENABLE		(1 << 25)
+#define   BLM_PHASE_IN_INTERUPT_ENABL	(1 << 24)
+#define   BLM_PHASE_IN_TIME_BASE_SHIFT	(16)
+#define   BLM_PHASE_IN_TIME_BASE_MASK	(0xff << 16)
+#define   BLM_PHASE_IN_COUNT_SHIFT	(8)
+#define   BLM_PHASE_IN_COUNT_MASK	(0xff << 8)
+#define   BLM_PHASE_IN_INCR_SHIFT	(0)
+#define   BLM_PHASE_IN_INCR_MASK	(0xff << 0)
+#define BLC_PWM_CTL		0x61254
 /*
  * This is the most significant 15 bits of the number of backlight cycles in a
  * complete cycle of the modulated backlight control.
  *
  * The actual value is this field multiplied by two.
  */
-#define   BACKLIGHT_MODULATION_FREQ_MASK		(0x7fff << 17)
-#define   BLM_LEGACY_MODE				(1 << 16)
+#define   BACKLIGHT_MODULATION_FREQ_SHIFT	(17)
+#define   BACKLIGHT_MODULATION_FREQ_MASK	(0x7fff << 17)
+#define   BLM_LEGACY_MODE			(1 << 16) /* gen2 only */
 /*
  * This is the number of cycles out of the backlight modulation cycle for which
  * the backlight is on.
@@ -1833,6 +1850,19 @@
 
 #define BLC_HIST_CTL		0x61260
 
+/* New registers for PCH-split platforms. Safe where new bits show up, the
+ * register layout machtes with gen4 BLC_PWM_CTL[12]. */
+#define BLC_PWM_CPU_CTL2	0x48250
+#define BLC_PWM_CPU_CTL		0x48254
+
+/* PCH CTL1 is totally different, all but the below bits are reserved. CTL2 is
+ * like the normal CTL from gen4 and earlier. Hooray for confusing naming. */
+#define BLC_PWM_PCH_CTL1	0xc8250
+#define   BLM_PCH_PWM_ENABLE			(1 << 30)
+#define   BLM_PCH_OVERRIDE_ENABLE		(1 << 30)
+#define   BLM_PCH_POLARITY			(1 << 29)
+#define BLC_PWM_PCH_CTL2	0xc8254
+
 /* TV port control */
 #define TV_CTL			0x68000
 /** Enables the TV encoder */
@@ -3840,21 +3870,6 @@
 #define PCH_LVDS	0xe1180
 #define  LVDS_DETECTED	(1 << 1)
 
-#define BLC_PWM_CPU_CTL2	0x48250
-#define  PWM_ENABLE		(1 << 31)
-#define  PWM_PIPE_A		(0 << 29)
-#define  PWM_PIPE_B		(1 << 29)
-#define BLC_PWM_CPU_CTL		0x48254
-
-#define BLC_PWM_PCH_CTL1	0xc8250
-#define  PWM_PCH_ENABLE		(1 << 31)
-#define  PWM_POLARITY_ACTIVE_LOW	(1 << 29)
-#define  PWM_POLARITY_ACTIVE_HIGH	(0 << 29)
-#define  PWM_POLARITY_ACTIVE_LOW2	(1 << 28)
-#define  PWM_POLARITY_ACTIVE_HIGH2	(0 << 28)
-
-#define BLC_PWM_PCH_CTL2	0xc8254
-
 #define PCH_PP_STATUS		0xc7200
 #define PCH_PP_CONTROL		0xc7204
 #define  PANEL_UNLOCK_REGS	(0xabcd << 16)
diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index 5e760319c0f2..bad36e0b8045 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -6895,9 +6895,9 @@ static void ivb_pch_pwm_override(struct drm_device *dev)
 	 * IVB has CPU eDP backlight regs too, set things up to let the
 	 * PCH regs control the backlight
 	 */
-	I915_WRITE(BLC_PWM_CPU_CTL2, PWM_ENABLE);
+	I915_WRITE(BLC_PWM_CPU_CTL2, BLM_PWM_ENABLE);
 	I915_WRITE(BLC_PWM_CPU_CTL, 0);
-	I915_WRITE(BLC_PWM_PCH_CTL1, PWM_ENABLE | (1<<30));
+	I915_WRITE(BLC_PWM_PCH_CTL1, BLM_PCH_PWM_ENABLE | BLM_PCH_OVERRIDE_ENABLE);
 }
 
 void intel_modeset_init_hw(struct drm_device *dev)
diff --git a/drivers/gpu/drm/i915/intel_lvds.c b/drivers/gpu/drm/i915/intel_lvds.c
index 08eb04c787e8..a7269e6b4bf7 100644
--- a/drivers/gpu/drm/i915/intel_lvds.c
+++ b/drivers/gpu/drm/i915/intel_lvds.c
@@ -1081,16 +1081,16 @@ out:
 
 		/* make sure PWM is enabled and locked to the LVDS pipe */
 		pwm = I915_READ(BLC_PWM_CPU_CTL2);
-		if (pipe == 0 && (pwm & PWM_PIPE_B))
-			I915_WRITE(BLC_PWM_CPU_CTL2, pwm & ~PWM_ENABLE);
+		if (pipe == 0 && (pwm & BLM_PIPE_B))
+			I915_WRITE(BLC_PWM_CPU_CTL2, pwm & ~BLM_PWM_ENABLE);
 		if (pipe)
-			pwm |= PWM_PIPE_B;
+			pwm |= BLM_PIPE_B;
 		else
-			pwm &= ~PWM_PIPE_B;
-		I915_WRITE(BLC_PWM_CPU_CTL2, pwm | PWM_ENABLE);
+			pwm &= ~BLM_PIPE_B;
+		I915_WRITE(BLC_PWM_CPU_CTL2, pwm | BLM_PWM_ENABLE);
 
 		pwm = I915_READ(BLC_PWM_PCH_CTL1);
-		pwm |= PWM_PCH_ENABLE;
+		pwm |= BLM_PCH_PWM_ENABLE;
 		I915_WRITE(BLC_PWM_PCH_CTL1, pwm);
 		/*
 		 * Unlock registers and just