1 files changed, 16 insertions, 2 deletions

diff --git a/drivers/gpu/drm/i915/intel_panel.c b/drivers/gpu/drm/i915/intel_panel.c
index 67e2c1f1c9a8..5950888ae1d0 100644
--- a/drivers/gpu/drm/i915/intel_panel.c
+++ b/drivers/gpu/drm/i915/intel_panel.c
@@ -497,8 +497,11 @@ void intel_panel_set_backlight(struct drm_device *dev, u32 level, u32 max)
                 goto out;
         }
 
-        /* scale to hardware */
-        level = level * freq / max;
+        /* scale to hardware, but be careful to not overflow */
+        if (freq < max)
+                level = level * freq / max;
+        else
+                level = freq / max * level;
 
         dev_priv->backlight.level = level;
         if (dev_priv->backlight.device)
@@ -515,6 +518,17 @@ void intel_panel_disable_backlight(struct drm_device *dev)
         struct drm_i915_private *dev_priv = dev->dev_private;
         unsigned long flags;
 
+        /*
+         * Do not disable backlight on the vgaswitcheroo path. When switching
+         * away from i915, the other client may depend on i915 to handle the
+         * backlight. This will leave the backlight on unnecessarily when
+         * another client is not activated.
+         */
+        if (dev->switch_power_state == DRM_SWITCH_POWER_CHANGING) {
+                DRM_DEBUG_DRIVER("Skipping backlight disable on vga switch\n");
+                return;
+        }
+
         spin_lock_irqsave(&dev_priv->backlight.lock, flags);
 
         dev_priv->backlight.enabled = false;