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@xxxxxxxxx>
On patch 1 and 2:
Reviewed-by: Imre Deak <imre.deak@xxxxxxxxx>
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.
> ---
> 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;
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