[Intel-gfx] [PATCH 1/3] drm/i915/bxt: add support for setting backlight freq from vbt

[Jani Nikula]

On Tue, 01 Dec 2015, Imre Deak <imre.deak at intel.com> wrote:
> On ti, 2015-12-01 at 10:23 +0200, Jani Nikula wrote:
>> The only missing piece is the function to convert frequency to PWM
>> register value. The PWM is based on 19.2 MHz clock, except for BXT A
>> step, which is based on CDCLK, and which we ignore.
>> 
>> Signed-off-by: Jani Nikula <jani.nikula at intel.com>
>
> On patch 1 and 2:
> Reviewed-by: Imre Deak <imre.deak at intel.com>
>
> For patch 3 we need an another reviewer.
>
> I also tested all three patches and they fix the backlight on BXT,
> before it was practically unusable: there was either no backlight at
> all or the backlight was flashing rapidly depending on the current
> backlight level.

Pushed all three to drm-intel-next-queued, thanks for the reviews, and
patch 3.

BR,
Jani.



>
>> ---
>>  drivers/gpu/drm/i915/intel_panel.c | 9 +++++++++
>>  1 file changed, 9 insertions(+)
>> 
>> diff --git a/drivers/gpu/drm/i915/intel_panel.c
>> b/drivers/gpu/drm/i915/intel_panel.c
>> index a24df35e11e7..2d1696386b0d 100644
>> --- a/drivers/gpu/drm/i915/intel_panel.c
>> +++ b/drivers/gpu/drm/i915/intel_panel.c
>> @@ -1264,6 +1264,14 @@ static void
>> intel_backlight_device_unregister(struct intel_connector *connector)
>>  #endif /* CONFIG_BACKLIGHT_CLASS_DEVICE */
>>  
>>  /*
>> + * BXT: PWM clock frequency = 19.2 MHz.
>> + */
>> +static u32 bxt_hz_to_pwm(struct intel_connector *connector, u32
>> pwm_freq_hz)
>> +{
>> +	return KHz(19200) / pwm_freq_hz;
>> +}
>> +
>> +/*
>>   * SPT: This value represents the period of the PWM stream in clock
>> periods
>>   * multiplied by 16 (default increment) or 128 (alternate increment
>> selected in
>>   * SCHICKEN_1 bit 0). PWM clock is 24 MHz.
>> @@ -1750,6 +1758,7 @@ intel_panel_init_backlight_funcs(struct
>> intel_panel *panel)
>>  		panel->backlight.disable = bxt_disable_backlight;
>>  		panel->backlight.set = bxt_set_backlight;
>>  		panel->backlight.get = bxt_get_backlight;
>> +		panel->backlight.hz_to_pwm = bxt_hz_to_pwm;
>>  	} else if (HAS_PCH_LPT(dev) || HAS_PCH_SPT(dev)) {
>>  		panel->backlight.setup = lpt_setup_backlight;
>>  		panel->backlight.enable = lpt_enable_backlight;

-- 
Jani Nikula, Intel Open Source Technology Center