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

[Jani Nikula <jani.nikula@linux.intel.com>]

On Wed, 08 Feb 2023, Ville Syrjälä <ville.syrjala@linux.intel.com> wrote:
> 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.

Agreed.

In any case, Cc: stable doesn't mean the commit actually backports
cleanly, but that it should be backported. Otherwise it'll just be
forgotten.


BR,
Jani.

>
>> 
>> > 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
>> > 

-- 
Jani Nikula, Intel Open Source Graphics Center