diff options
Diffstat (limited to 'drivers/gpu/drm/i915/intel_panel.c')
| -rw-r--r-- | drivers/gpu/drm/i915/intel_panel.c | 22 |
1 files changed, 17 insertions, 5 deletions
diff --git a/drivers/gpu/drm/i915/intel_panel.c b/drivers/gpu/drm/i915/intel_panel.c index 18784470a760..41b3be217493 100644 --- a/drivers/gpu/drm/i915/intel_panel.c +++ b/drivers/gpu/drm/i915/intel_panel.c @@ -419,9 +419,8 @@ static uint32_t scale(uint32_t source_val, source_val = clamp(source_val, source_min, source_max); /* avoid overflows */ - target_val = (uint64_t)(source_val - source_min) * - (target_max - target_min); - do_div(target_val, source_max - source_min); + target_val = DIV_ROUND_CLOSEST_ULL((uint64_t)(source_val - source_min) * + (target_max - target_min), source_max - source_min); target_val += target_min; return target_val; @@ -1099,12 +1098,25 @@ static u32 get_backlight_min_vbt(struct intel_connector *connector) struct drm_device *dev = connector->base.dev; struct drm_i915_private *dev_priv = dev->dev_private; struct intel_panel *panel = &connector->panel; + int min; WARN_ON(panel->backlight.max == 0); + /* + * XXX: If the vbt value is 255, it makes min equal to max, which leads + * to problems. There are such machines out there. Either our + * interpretation is wrong or the vbt has bogus data. Or both. Safeguard + * against this by letting the minimum be at most (arbitrarily chosen) + * 25% of the max. + */ + min = clamp_t(int, dev_priv->vbt.backlight.min_brightness, 0, 64); + if (min != dev_priv->vbt.backlight.min_brightness) { + DRM_DEBUG_KMS("clamping VBT min backlight %d/255 to %d/255\n", + dev_priv->vbt.backlight.min_brightness, min); + } + /* vbt value is a coefficient in range [0..255] */ - return scale(dev_priv->vbt.backlight.min_brightness, 0, 255, - 0, panel->backlight.max); + return scale(min, 0, 255, 0, panel->backlight.max); } static int bdw_setup_backlight(struct intel_connector *connector) |