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.
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.f...@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
