On Thu, Oct 8, 2020 at 1:07 PM Lyude Paul <lyude@redhat.com> wrote:

oh hold on, I misspoke. Here's the patch I was thinking of:

https://patchwork.freedesktop.org/series/82041/

On Thu, 2020-10-08 at 10:32 +0800, Kai-Heng Feng wrote:
> Hi Lyude,
>
> > On Oct 8, 2020, at 05:53, Lyude Paul <lyude@redhat.com> wrote:
> >
> > Hi! I thought this patch rang a bell, we actually already had some
> > discussion
> > about this since there's a couple of other systems this was causing issues
> > for.
> > Unfortunately it never seems like that patch got sent out. Satadru?
> >
> > (if I don't hear back from them soon, I'll just send out a patch for this
> > myself)
> >
> > JFYI - the proper fix here is to just drop the
> > DP_EDP_BACKLIGHT_BRIGHTNESS_PWM_PIN_CAP check from the code entirely. As
> > long as
> > the backlight supports AUX_SET_CAP, that should be enough for us to control
> > it.
>
> Does the proper fix include dropping DP_QUIRK_FORCE_DPCD_BACKLIGHT entirely?
>
> Kai-Heng
>
> >
> > On Wed, 2020-10-07 at 14:58 +0800, Kai-Heng Feng wrote:
> > > HP DreamColor panel needs to be controlled via AUX interface. However,
> > > it has both DP_EDP_BACKLIGHT_BRIGHTNESS_AUX_SET_CAP and
> > > DP_EDP_BACKLIGHT_BRIGHTNESS_PWM_PIN_CAP set, so it fails to pass
> > > intel_dp_aux_display_control_capable() test.
> > >
> > > Skip the test if the panel has force DPCD quirk.
> > >
> > > Signed-off-by: Kai-Heng Feng <kai.heng.feng@canonical.com>
> > > ---
> > > drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c | 10 ++++++----
> > > 1 file changed, 6 insertions(+), 4 deletions(-)
> > >
> > > diff --git a/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c
> > > b/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c
> > > index acbd7eb66cbe..acf2e1c65290 100644
> > > --- a/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c
> > > +++ b/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c
> > > @@ -347,9 +347,13 @@ int intel_dp_aux_init_backlight_funcs(struct
> > > intel_connector *intel_connector)
> > > struct intel_panel *panel = &intel_connector->panel;
> > > struct intel_dp *intel_dp = enc_to_intel_dp(intel_connector->encoder);
> > > struct drm_i915_private *i915 = dp_to_i915(intel_dp);
> > > + bool force_dpcd;
> > > +
> > > + force_dpcd = drm_dp_has_quirk(&intel_dp->desc, intel_dp->edid_quirks,
> > > + DP_QUIRK_FORCE_DPCD_BACKLIGHT);
> > >
> > > if (i915->params.enable_dpcd_backlight == 0 ||
> > > - !intel_dp_aux_display_control_capable(intel_connector))
> > > + (!force_dpcd &&
> > > !intel_dp_aux_display_control_capable(intel_connector)))
> > > return -ENODEV;
> > >
> > > /*
> > > @@ -358,9 +362,7 @@ int intel_dp_aux_init_backlight_funcs(struct
> > > intel_connector *intel_connector)
> > > */
> > > if (i915->vbt.backlight.type !=
> > > INTEL_BACKLIGHT_VESA_EDP_AUX_INTERFACE &&
> > > - i915->params.enable_dpcd_backlight != 1 &&
> > > - !drm_dp_has_quirk(&intel_dp->desc, intel_dp->edid_quirks,
> > > - DP_QUIRK_FORCE_DPCD_BACKLIGHT)) {
> > > + i915->params.enable_dpcd_backlight != 1 && !force_dpcd) {
> > > drm_info(&i915->drm,
> > > "Panel advertises DPCD backlight support, but "
> > > "VBT disagrees. If your backlight controls "
> > --
> > Sincerely,
> > Lyude Paul (she/her)
> > Software Engineer at Red Hat
--
Sincerely,
Lyude Paul (she/her)
Software Engineer at Red Hat