1 files changed, 32 insertions, 14 deletions

diff --git a/drivers/gpu/drm/i915/intel_panel.c b/drivers/gpu/drm/i915/intel_panel.c
index 10c7d39034e1..e019b2369861 100644
--- a/drivers/gpu/drm/i915/intel_panel.c
+++ b/drivers/gpu/drm/i915/intel_panel.c
@@ -162,19 +162,12 @@ static u32 i915_read_blc_pwm_ctl(struct drm_i915_private *dev_priv)
         return val;
 }
 
-u32 intel_panel_get_max_backlight(struct drm_device *dev)
+static u32 _intel_panel_get_max_backlight(struct drm_device *dev)
 {
         struct drm_i915_private *dev_priv = dev->dev_private;
         u32 max;
 
         max = i915_read_blc_pwm_ctl(dev_priv);
-        if (max == 0) {
-                /* XXX add code here to query mode clock or hardware clock
-                 * and program max PWM appropriately.
-                 */
-                pr_warn_once("fixme: max PWM is zero\n");
-                return 1;
-        }
 
         if (HAS_PCH_SPLIT(dev)) {
                 max >>= 16;
@@ -188,6 +181,22 @@ u32 intel_panel_get_max_backlight(struct drm_device *dev)
                         max *= 0xff;
         }
 
+        return max;
+}
+
+u32 intel_panel_get_max_backlight(struct drm_device *dev)
+{
+        u32 max;
+
+        max = _intel_panel_get_max_backlight(dev);
+        if (max == 0) {
+                /* XXX add code here to query mode clock or hardware clock
+                 * and program max PWM appropriately.
+                 */
+                pr_warn_once("fixme: max PWM is zero\n");
+                return 1;
+        }
+
         DRM_DEBUG_DRIVER("max backlight PWM = %d\n", max);
         return max;
 }
@@ -213,7 +222,7 @@ static u32 intel_panel_compute_brightness(struct drm_device *dev, u32 val)
         return val;
 }
 
-u32 intel_panel_get_backlight(struct drm_device *dev)
+static u32 intel_panel_get_backlight(struct drm_device *dev)
 {
         struct drm_i915_private *dev_priv = dev->dev_private;
         u32 val;
@@ -311,9 +320,6 @@ void intel_panel_enable_backlight(struct drm_device *dev,
         if (dev_priv->backlight_level == 0)
                 dev_priv->backlight_level = intel_panel_get_max_backlight(dev);
 
-        dev_priv->backlight_enabled = true;
-        intel_panel_actually_set_backlight(dev, dev_priv->backlight_level);
-
         if (INTEL_INFO(dev)->gen >= 4) {
                 uint32_t reg, tmp;
 
@@ -326,7 +332,7 @@ void intel_panel_enable_backlight(struct drm_device *dev,
                  * we don't track the backlight dpms state, hence check whether
                  * we have to do anything first. */
                 if (tmp & BLM_PWM_ENABLE)
-                        return;
+                        goto set_level;
 
                 if (dev_priv->num_pipe == 3)
                         tmp &= ~BLM_PIPE_SELECT_IVB;
@@ -347,6 +353,14 @@ void intel_panel_enable_backlight(struct drm_device *dev,
                         I915_WRITE(BLC_PWM_PCH_CTL1, tmp);
                 }
         }
+
+set_level:
+        /* Call below after setting BLC_PWM_CPU_CTL2 and BLC_PWM_PCH_CTL1.
+         * BLC_PWM_CPU_CTL may be cleared to zero automatically when these
+         * registers are set.
+         */
+        dev_priv->backlight_enabled = true;
+        intel_panel_actually_set_backlight(dev, dev_priv->backlight_level);
 }
 
 static void intel_panel_init_backlight(struct drm_device *dev)
@@ -419,7 +433,11 @@ int intel_panel_setup_backlight(struct drm_device *dev)
 
         memset(&props, 0, sizeof(props));
         props.type = BACKLIGHT_RAW;
-        props.max_brightness = intel_panel_get_max_backlight(dev);
+        props.max_brightness = _intel_panel_get_max_backlight(dev);
+        if (props.max_brightness == 0) {
+                DRM_ERROR("Failed to get maximum backlight value\n");
+                return -ENODEV;
+        }
         dev_priv->backlight =
                 backlight_device_register("intel_backlight",
                                           &connector->kdev, dev,