Re: [PATCH] drm/i915: Correctly read backlight PWM for pipe B on vlv/chv

["Ville Syrjälä" <ville.syrjala@linux.intel.com>]

On Tue, Jul 29, 2014 at 01:44:40PM +0100, rafael.barbalho@intel.com wrote:
> From: Rafael Barbalho <rafael.barbalho@intel.com>
> 
> Make the vlv/chv backlight setup more generic by actually looking at which
> pipe the panel is attached to and read the backlight PWM registers that were
> setup by the bios from that pipe.
> 
> Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
> Signed-off-by: Rafael Barbalho <rafael.barbalho@intel.com>
> ---
>  drivers/gpu/drm/i915/intel_panel.c | 24 ++++++++++--------------
>  1 file changed, 10 insertions(+), 14 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/intel_panel.c b/drivers/gpu/drm/i915/intel_panel.c
> index 59b028f..be75d76 100644
> --- a/drivers/gpu/drm/i915/intel_panel.c
> +++ b/drivers/gpu/drm/i915/intel_panel.c
> @@ -1200,32 +1200,28 @@ static int vlv_setup_backlight(struct intel_connector *connector)
>  	struct drm_device *dev = connector->base.dev;
>  	struct drm_i915_private *dev_priv = dev->dev_private;
>  	struct intel_panel *panel = &connector->panel;
> -	enum pipe pipe;
> +	enum pipe pipe = intel_get_pipe_from_connector(connector);

This won't work unless the connector is already enabled.

The power sequencer has a similar problem where we have to somehow deduce
the correct pipe. vlv_power_sequencer_pipe() tries to guess the correct pipe
there.

We could start with intel_get_pipe_from_connector() and if that fails we'd
do something like vlv_power_sequencer_pipe(). Hmm, except the backlight
registers don't have the port information, so I guess we'd need to pick the
pipe simply based on the DP port control register.

>  	u32 ctl, ctl2, val;
>  
> -	for_each_pipe(pipe) {
> -		u32 cur_val = I915_READ(VLV_BLC_PWM_CTL(pipe));
> +	ctl2 = I915_READ(VLV_BLC_PWM_CTL2(pipe));
> +	panel->backlight.active_low_pwm = ctl2 & BLM_POLARITY_I965;
>  
> -		/* Skip if the modulation freq is already set */
> -		if (cur_val & ~BACKLIGHT_DUTY_CYCLE_MASK)
> -			continue;
> +	ctl = I915_READ(VLV_BLC_PWM_CTL(pipe));
>  
> -		cur_val &= BACKLIGHT_DUTY_CYCLE_MASK;
> -		I915_WRITE(VLV_BLC_PWM_CTL(pipe), (0xf42 << 16) |
> -			   cur_val);
> +	/* Skip if the modulation freq is already set */
> +	if ((ctl & ~BACKLIGHT_DUTY_CYCLE_MASK) == 0) {
> +		ctl &= BACKLIGHT_DUTY_CYCLE_MASK;
> +		ctl |= (0xf42 << 16);
> +		I915_WRITE(VLV_BLC_PWM_CTL(pipe), ctl);
>  	}
>  
> -	ctl2 = I915_READ(VLV_BLC_PWM_CTL2(PIPE_A));
> -	panel->backlight.active_low_pwm = ctl2 & BLM_POLARITY_I965;
> -
> -	ctl = I915_READ(VLV_BLC_PWM_CTL(PIPE_A));
>  	panel->backlight.max = ctl >> 16;
>  	if (!panel->backlight.max)
>  		return -ENODEV;
>  
>  	panel->backlight.min = get_backlight_min_vbt(connector);
>  
> -	val = _vlv_get_backlight(dev, PIPE_A);
> +	val = _vlv_get_backlight(dev, pipe);
>  	panel->backlight.level = intel_panel_compute_brightness(connector, val);
>  
>  	panel->backlight.enabled = (ctl2 & BLM_PWM_ENABLE) &&
> -- 
> 2.0.3

-- 
Ville Syrjälä
Intel OTC