[Intel-gfx] [PATCH] drm/i915: fix backlight invert for non-zero minimum brightness

[Daniel Vetter]

On Wed, May 31, 2017 at 11:33:55AM +0300, Jani Nikula wrote:
> When we started following the backlight minimum brightness in
> 6dda730e55f4 ("drm/i915: respect the VBT minimum backlight brightness")
> we overlooked the brightness invert quirk. Even if we invert the
> brightness, we need to take the min limit into account. We probably
> missed this because the invert has only been required on gen4 for proper
> operation.
> 
> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=101127
> Fixes: 6dda730e55f4 ("drm/i915: respect the VBT minimum backlight brightness")
> Cc: Daniel Vetter <daniel.vetter at ffwll.ch>
> Cc: <stable at vger.kernel.org> # v3.17+

Not sure the cc: stable is justified, but makes sense otherwise

Reviewed-by: Daniel Vetter <daniel.vetter at ffwll.ch>

> Signed-off-by: Jani Nikula <jani.nikula at intel.com>
> ---
>  drivers/gpu/drm/i915/intel_panel.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/i915/intel_panel.c b/drivers/gpu/drm/i915/intel_panel.c
> index cb50c527401f..bcde9f34527a 100644
> --- a/drivers/gpu/drm/i915/intel_panel.c
> +++ b/drivers/gpu/drm/i915/intel_panel.c
> @@ -469,7 +469,7 @@ static u32 intel_panel_compute_brightness(struct intel_connector *connector,
>  
>  	if (i915.invert_brightness > 0 ||
>  	    dev_priv->quirks & QUIRK_INVERT_BRIGHTNESS) {
> -		return panel->backlight.max - val;
> +		return panel->backlight.max - val + panel->backlight.min;
>  	}
>  
>  	return val;
> -- 
> 2.11.0
> 

-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch