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

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

[Jani Nikula]

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@ffwll.ch>
Cc: <stable@vger.kernel.org> # v3.17+
Signed-off-by: Jani Nikula <jani.nikula@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

Re: [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@ffwll.ch>
> Cc: <stable@vger.kernel.org> # v3.17+

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

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

> Signed-off-by: Jani Nikula <jani.nikula@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

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

[Jani Nikula]

On Wed, 31 May 2017, Daniel Vetter <daniel@ffwll.ch> wrote:
> 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@ffwll.ch>
>> Cc: <stable@vger.kernel.org> # v3.17+
>
> Not sure the cc: stable is justified, but makes sense otherwise
>
> Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>

Had forgotten about this, pushed now, without cc: stable.

Thanks for the review.

BR,
Jani.


>
>> Signed-off-by: Jani Nikula <jani.nikula@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
>> 

-- 
Jani Nikula, Intel Open Source Technology Center