Re: [Intel-gfx] [PATCH] drm/i915/bios: set default backlight controller index

[Jani Nikula <jani.nikula@intel.com>]

On Tue, 07 Feb 2023, Ville Syrjälä <ville.syrjala@linux.intel.com> wrote:
> On Tue, Feb 07, 2023 at 01:16:26PM +0200, Jani Nikula wrote:
>> With backlight controller set to -1 in intel_panel_init_alloc() to
>> distinguish uninitialized values, and controller later being set only if
>> it's present in VBT, we can end up with -1 for the controller:
>> 
>>     [drm:intel_bios_init_panel [i915]] VBT backlight PWM modulation
>>     frequency 200 Hz, active high, min brightness 0, level 255,
>>     controller 4294967295
>> 
>> There's no harm if it happens on platforms that ignore controller due to
>> only one backlight controller being present, like on VLV above, but play
>> it safe.
>> 
>> Fixes: bf38bba3e7d6 ("drm/i915: Try to use the correct power sequencer intiially on bxt/glk")
>> Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
>> Signed-off-by: Jani Nikula <jani.nikula@intel.com>
>> ---
>>  drivers/gpu/drm/i915/display/intel_bios.c | 1 +
>>  1 file changed, 1 insertion(+)
>> 
>> diff --git a/drivers/gpu/drm/i915/display/intel_bios.c b/drivers/gpu/drm/i915/display/intel_bios.c
>> index e6ca51232dcf..ad833069f59c 100644
>> --- a/drivers/gpu/drm/i915/display/intel_bios.c
>> +++ b/drivers/gpu/drm/i915/display/intel_bios.c
>> @@ -1033,6 +1033,7 @@ parse_lfp_backlight(struct drm_i915_private *i915,
>>  	}
>>  
>>  	panel->vbt.backlight.type = INTEL_BACKLIGHT_DISPLAY_DDI;
>> +	panel->vbt.backlight.controller = 0;
>>  	if (i915->display.vbt.version >= 191) {
>>  		size_t exp_size;
>
> Ah right, older VBT didnt have this so we leave it untouched.
> Zeroing in that case seems like the right thing to do.
>
> Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>

Thanks, pushed to din.

BR,
Jani.

-- 
Jani Nikula, Intel Open Source Graphics Center