Hi Lyude,
> On Oct 8, 2020, at 05:53, Lyude Paul <lyude@xxxxxxxxxx> 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@xxxxxxxxxxxxx>
>> ---
>> 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
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