On Fri, 17 Jan 2020, Lyude Paul <lyude@xxxxxxxxxx> wrote: > Despite the fact that the VBT appears to have a field for specifying > that a system is equipped with a panel that supports standard VESA > backlight controls over the DP AUX channel, so far every system we've > spotted DPCD backlight control support on doesn't actually set this > field correctly and all have it set to INTEL_BACKLIGHT_DISPLAY_DDI. > > While we don't know the exact reason for this VBT misuse, talking with > some vendors indicated that there's a good number of laptop panels out > there that supposedly support both PWM backlight controls and DPCD > backlight controls as a workaround until Intel supports DPCD backlight > controls across platforms universally. This being said, the X1 Extreme > 2nd Gen that I have here (note that Lenovo is not the hardware vendor > that informed us of this) PWM backlight controls are advertised, but > only DPCD controls actually function. I'm going to make an educated > guess here and say that on systems like this one, it's likely that PWM > backlight controls might have been intended to work but were never > really tested by QA. > > Since we really need backlights to work without any extra module > parameters, let's take the risk here and rely on the standard DPCD caps > to tell us whether AUX backlight controls are supported or not. We still > check the VBT, just so we can print a debugging message on systems that > advertise DPCD backlight support on the panel but not in the VBT. > > Changes since v3: > * Print a debugging message if we enable DPCD backlight control on a > device which doesn't report DPCD backlight controls in it's VBT, > instead of warning on custom panel backlight interfaces. > > Signed-off-by: Lyude Paul <lyude@xxxxxxxxxx> > Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=112376 > Cc: Jani Nikula <jani.nikula@xxxxxxxxx> > Cc: Perry Yuan <pyuan@xxxxxxxxxx> > Cc: AceLan Kao <acelan.kao@xxxxxxxxxxxxx> Thanks for the patch, pushed to dinq, fingers crossed! ;) BR, Jani. > --- > drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c | 9 +++++---- > 1 file changed, 5 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 77a759361c5c..0f8edc775375 100644 > --- a/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c > +++ b/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c > @@ -328,15 +328,16 @@ intel_dp_aux_display_control_capable(struct intel_connector *connector) > int intel_dp_aux_init_backlight_funcs(struct intel_connector *intel_connector) > { > struct intel_panel *panel = &intel_connector->panel; > - struct drm_i915_private *dev_priv = to_i915(intel_connector->base.dev); > + enum intel_backlight_type type = > + to_i915(intel_connector->base.dev)->vbt.backlight.type; > > if (i915_modparams.enable_dpcd_backlight == 0 || > (i915_modparams.enable_dpcd_backlight == -1 && > - dev_priv->vbt.backlight.type != INTEL_BACKLIGHT_VESA_EDP_AUX_INTERFACE)) > + !intel_dp_aux_display_control_capable(intel_connector))) > return -ENODEV; > > - if (!intel_dp_aux_display_control_capable(intel_connector)) > - return -ENODEV; > + if (type != INTEL_BACKLIGHT_VESA_EDP_AUX_INTERFACE) > + DRM_DEBUG_DRIVER("Ignoring VBT backlight type\n"); > > panel->backlight.setup = intel_dp_aux_setup_backlight; > panel->backlight.enable = intel_dp_aux_enable_backlight; -- Jani Nikula, Intel Open Source Graphics Center _______________________________________________ Intel-gfx mailing list Intel-gfx@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/intel-gfx
