drm/i915: avoid brightness overflow when doing scale

[linux-imx.git] / drivers / gpu / drm / i915 / intel_panel.c

diff --git a/drivers/gpu/drm/i915/intel_panel.c b/drivers/gpu/drm/i915/intel_panel.c
index 45010bb5d1321071b3ba1238200f658b4bb02e6b..5063eadac3ef5fc1a2966ccb081ae4bc2aaf8ad1 100644 (file)
--- 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)
@@ -583,7 +586,8 @@ void intel_panel_enable_backlight(struct drm_device *dev,
                POSTING_READ(reg);
                I915_WRITE(reg, tmp | BLM_PWM_ENABLE);
 
-               if (HAS_PCH_SPLIT(dev)) {
+               if (HAS_PCH_SPLIT(dev) &&
+                   !(dev_priv->quirks & QUIRK_NO_PCH_PWM_ENABLE)) {
                        tmp = I915_READ(BLC_PWM_PCH_CTL1);
                        tmp |= BLM_PCH_PWM_ENABLE;
                        tmp &= ~BLM_PCH_OVERRIDE_ENABLE;