Re: [Intel-gfx] [PATCH 3/3] drm/i915: Pick the backlight controller based on VBT on ICP+

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

On Wed, Feb 08, 2023 at 10:23:55AM -0500, Rodrigo Vivi wrote:
> On Tue, Feb 07, 2023 at 08:43:37AM +0200, Ville Syrjala wrote:
> > From: Ville Syrjälä <ville.syrjala@linux.intel.com>
> > 
> > Use the second backlight controller on ICP+ if the VBT asks
> > us to do so.
> > 
> > On pre-MTP we also check the chicken bit to make sure the
> > pins have been correctly muxed by the firmware.
> > 
> 
> It looks like CC: stable was added while merging this patch.
> But it doesn't go clean. build fails due to s/dev_priv/i915
> and also due to the lack of ICP_SECOND_PPS_IO_SELECT that
> was added by another patch.
> 
> So we need a backported version of this patch to be included
> in the stable trees... how far we will go in the stable tree?
> 
> At this point of -rc7 I even wonder it will be better to stay
> for 6.2 to get released and then send the backported version
> to the stable ml directly...

Yeah, let's attempt the backport after 6.2 is out.

> 
> > Closes: https://gitlab.freedesktop.org/drm/intel/-/issues/8016
> > Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
> > ---
> >  .../gpu/drm/i915/display/intel_backlight.c    | 34 +++++++++++++++++--
> >  1 file changed, 31 insertions(+), 3 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/i915/display/intel_backlight.c b/drivers/gpu/drm/i915/display/intel_backlight.c
> > index 5b7da72c95b8..a4e4b7f79e4d 100644
> > --- a/drivers/gpu/drm/i915/display/intel_backlight.c
> > +++ b/drivers/gpu/drm/i915/display/intel_backlight.c
> > @@ -1431,6 +1431,30 @@ bxt_setup_backlight(struct intel_connector *connector, enum pipe unused)
> >  	return 0;
> >  }
> >  
> > +static int cnp_num_backlight_controllers(struct drm_i915_private *i915)
> > +{
> > +	if (INTEL_PCH_TYPE(i915) >= PCH_DG1)
> > +		return 1;
> > +
> > +	if (INTEL_PCH_TYPE(i915) >= PCH_ICP)
> > +		return 2;
> > +
> > +	return 1;
> > +}
> > +
> > +static bool cnp_backlight_controller_is_valid(struct drm_i915_private *i915, int controller)
> > +{
> > +	if (controller < 0 || controller >= cnp_num_backlight_controllers(i915))
> > +		return false;
> > +
> > +	if (controller == 1 &&
> > +	    INTEL_PCH_TYPE(i915) >= PCH_ICP &&
> > +	    INTEL_PCH_TYPE(i915) < PCH_MTP)
> > +		return intel_de_read(i915, SOUTH_CHICKEN1) & ICP_SECOND_PPS_IO_SELECT;
> > +
> > +	return true;
> > +}
> > +
> >  static int
> >  cnp_setup_backlight(struct intel_connector *connector, enum pipe unused)
> >  {
> > @@ -1440,10 +1464,14 @@ cnp_setup_backlight(struct intel_connector *connector, enum pipe unused)
> >  
> >  	/*
> >  	 * CNP has the BXT implementation of backlight, but with only one
> > -	 * controller. TODO: ICP has multiple controllers but we only use
> > -	 * controller 0 for now.
> > +	 * controller. ICP+ can have two controllers, depending on pin muxing.
> >  	 */
> > -	panel->backlight.controller = 0;
> > +	panel->backlight.controller = connector->panel.vbt.backlight.controller;
> > +	if (!cnp_backlight_controller_is_valid(i915, panel->backlight.controller)) {
> > +		drm_dbg_kms(&i915->drm, "Invalid backlight controller %d, assuming 0\n",
> > +			    panel->backlight.controller);
> > +		panel->backlight.controller = 0;
> > +	}
> >  
> >  	pwm_ctl = intel_de_read(i915,
> >  				BXT_BLC_PWM_CTL(panel->backlight.controller));
> > -- 
> > 2.39.1
> > 

-- 
Ville Syrjälä
Intel