On Fri, 2020-01-17 at 13:36 +0200, Jani Nikula wrote: > On Thu, 16 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, but only to make sure that we don't enable DPCD backlight > > controls on a panel that uses something other then the standard VESA > > interfaces over AUX. Since panels using such non-standard interfaces > > should probably have support added to i915, we'll print a warning when > > seeing this in the VBT. We can remove this warning later if we end up > > adding support for any custom 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> > > --- > > .../drm/i915/display/intel_dp_aux_backlight.c | 16 ++++++++++------ > > 1 file changed, 10 insertions(+), 6 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..3002b600635f 100644 > > --- a/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c > > +++ b/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c > > @@ -330,13 +330,17 @@ 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); > > > > - if (i915_modparams.enable_dpcd_backlight == 0 || > > - (i915_modparams.enable_dpcd_backlight == -1 && > > - dev_priv->vbt.backlight.type != > > INTEL_BACKLIGHT_VESA_EDP_AUX_INTERFACE)) > > - return -ENODEV; > > - > > - if (!intel_dp_aux_display_control_capable(intel_connector)) > > + if (i915_modparams.enable_dpcd_backlight == 0) > > return -ENODEV; > > + if (i915_modparams.enable_dpcd_backlight == -1) { > > + if (dev_priv->vbt.backlight.type > > + == INTEL_BACKLIGHT_PANEL_DRIVER_INTERFACE) { > > + DRM_WARN("VBT says panel uses custom panel driver > > interface, not using DPCD backlight controls\n"); > > + return -ENODEV; > > + } > > + if (!intel_dp_aux_display_control_capable(intel_connector)) > > + return -ENODEV; > > Functionally, I'm fine with trying this. But perhaps we should check aux > and early return first, and then check what vbt says, to reduce the > dmesg noise. > > I'll probably want to see a debug message if we're enabling aux > backlight even if dev_priv->vbt.backlight.type != > INTEL_BACKLIGHT_VESA_EDP_AUX_INTERFACE. It's the kind of debug trace > you'll really want to get first. Good point, I'll send a respin of this patch with those changes > > BR, > Jani. > > > > > + } > > > > panel->backlight.setup = intel_dp_aux_setup_backlight; > > panel->backlight.enable = intel_dp_aux_enable_backlight; -- Cheers, Lyude Paul _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/dri-devel
