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

[Barbalho, Rafael]

> -----Original Message-----
> From: Ville Syrjälä [mailto:ville.syrjala at linux.intel.com]
> Sent: Tuesday, July 29, 2014 2:13 PM
> To: Barbalho, Rafael
> Cc: intel-gfx at lists.freedesktop.org
> Subject: Re: [PATCH] drm/i915: Correctly read backlight PWM for pipe B on
> vlv/chv
> 
> On Tue, Jul 29, 2014 at 01:44:40PM +0100, rafael.barbalho at intel.com wrote:
> > From: Rafael Barbalho <rafael.barbalho at 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 at linux.intel.com>
> > Signed-off-by: Rafael Barbalho <rafael.barbalho at 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.
> 

Fair point, I didn't realise that intel_get_pipe_from_connector could return INVALID_PIPE. 

How about if I add:
+	enum pipe pipe = intel_get_pipe_from_connector(connector);
+
+	if (pipe == INVALID_PIPE)
+		pipe = PIPE_A;

It would return the driver to the current behaviour but still enable pipe B when that is present
at start up. 

> >  	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