2 files changed, 46 insertions, 0 deletions

diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
index 3e6f486f4605..2abe240dae58 100644
--- a/drivers/gpu/drm/i915/i915_reg.h
+++ b/drivers/gpu/drm/i915/i915_reg.h
@@ -1553,7 +1553,17 @@
 
 /* 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)
+/*
+ * 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)
 /*
  * This is the number of cycles out of the backlight modulation cycle for which
  * the backlight is on.
diff --git a/drivers/gpu/drm/i915/intel_panel.c b/drivers/gpu/drm/i915/intel_panel.c
index d860abeda70f..f8f86e57df22 100644
--- a/drivers/gpu/drm/i915/intel_panel.c
+++ b/drivers/gpu/drm/i915/intel_panel.c
@@ -30,6 +30,8 @@
 
 #include "intel_drv.h"
 
+#define PCI_LBPC 0xf4 /* legacy/combination backlight modes */
+
 void
 intel_fixed_panel_mode(struct drm_display_mode *fixed_mode,
                        struct drm_display_mode *adjusted_mode)
@@ -110,6 +112,19 @@ done:
         dev_priv->pch_pf_size = (width << 16) | height;
 }
 
+static int is_backlight_combination_mode(struct drm_device *dev)
+{
+        struct drm_i915_private *dev_priv = dev->dev_private;
+
+        if (INTEL_INFO(dev)->gen >= 4)
+                return I915_READ(BLC_PWM_CTL2) & BLM_COMBINATION_MODE;
+
+        if (IS_GEN2(dev))
+                return I915_READ(BLC_PWM_CTL) & BLM_LEGACY_MODE;
+
+        return 0;
+}
+
 static u32 i915_read_blc_pwm_ctl(struct drm_i915_private *dev_priv)
 {
         u32 val;
@@ -166,6 +181,9 @@ u32 intel_panel_get_max_backlight(struct drm_device *dev)
                         if (INTEL_INFO(dev)->gen < 4)
                                 max &= ~1;
                 }
+
+                if (is_backlight_combination_mode(dev))
+                        max *= 0xff;
         }
 
         DRM_DEBUG_DRIVER("max backlight PWM = %d\n", max);
@@ -183,6 +201,14 @@ u32 intel_panel_get_backlight(struct drm_device *dev)
                 val = I915_READ(BLC_PWM_CTL) & BACKLIGHT_DUTY_CYCLE_MASK;
                 if (IS_PINEVIEW(dev))
                         val >>= 1;
+
+                if (is_backlight_combination_mode(dev)){
+                        u8 lbpc;
+
+                        val &= ~1;
+                        pci_read_config_byte(dev->pdev, PCI_LBPC, &lbpc);
+                        val *= lbpc;
+                }
         }
 
         DRM_DEBUG_DRIVER("get backlight PWM = %d\n", val);
@@ -205,6 +231,16 @@ void intel_panel_set_backlight(struct drm_device *dev, u32 level)
 
         if (HAS_PCH_SPLIT(dev))
                 return intel_pch_panel_set_backlight(dev, level);
+
+        if (is_backlight_combination_mode(dev)){
+                u32 max = intel_panel_get_max_backlight(dev);
+                u8 lbpc;
+
+                lbpc = level * 0xfe / max + 1;
+                level /= lbpc;
+                pci_write_config_byte(dev->pdev, PCI_LBPC, lbpc);
+        }
+
         tmp = I915_READ(BLC_PWM_CTL);
         if (IS_PINEVIEW(dev)) {
                 tmp &= ~(BACKLIGHT_DUTY_CYCLE_MASK - 1);