[Intel-gfx] [PATCH 3/4] drm/i915/dp: make backlight bl_power control power sequencer backlight

[Clint Taylor]

On 08/12/2014 07:11 AM, Jani Nikula wrote:
> This lets the userspace switch off the backlight using the backlight
> class sysfs bl_power file. The switch is done using the power sequencer;
> the backlight PWM, and everything else, remains enabled. The display
> backlight won't draw power, but for maximum power savings the encoder
> needs to be switched off.
>
> Signed-off-by: Jani Nikula <jani.nikula at intel.com>
> ---
>   drivers/gpu/drm/i915/intel_dp.c | 22 ++++++++++++++++++++++
>   1 file changed, 22 insertions(+)
>
> diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
> index d8baf60ff3fd..f6e3e9a906b0 100644
> --- a/drivers/gpu/drm/i915/intel_dp.c
> +++ b/drivers/gpu/drm/i915/intel_dp.c
> @@ -1453,6 +1453,27 @@ void intel_edp_backlight_off(struct intel_dp *intel_dp)
>   	intel_panel_disable_backlight(intel_dp->attached_connector);
>   }
>
> +/*
> + * Hook for controlling the panel power control backlight through the bl_power
> + * sysfs attribute. Take care to handle multiple calls.
> + */
> +static void intel_edp_backlight_power(struct intel_connector *connector,
> +				      bool enable)
> +{
> +	struct intel_dp *intel_dp = intel_attached_dp(&connector->base);
> +	bool is_enabled = ironlake_get_pp_control(intel_dp) & EDP_BLC_ENABLE;
> +
> +	if (is_enabled == enable)
> +		return;
> +
> +	DRM_DEBUG_KMS("\n");
> +
> +	if (enable)
> +		_intel_edp_backlight_on(intel_dp);
> +	else
> +		_intel_edp_backlight_off(intel_dp);

Is there a good reason why we leave the PWM enabled? There is a small 
power requirement to leave the PWM enabled.

> +}
> +
>   static void ironlake_edp_pll_on(struct intel_dp *intel_dp)
>   {
>   	struct intel_digital_port *intel_dig_port = dp_to_dig_port(intel_dp);
> @@ -4579,6 +4600,7 @@ static bool intel_edp_init_connector(struct intel_dp *intel_dp,
>   	}
>
>   	intel_panel_init(&intel_connector->panel, fixed_mode, downclock_mode);
> +	intel_connector->panel.backlight_power = intel_edp_backlight_power;
>   	intel_panel_setup_backlight(connector);
>
>   	return true;
>