On Tue, 16 Jun 2026, Arun R Murthy <[email protected]> wrote: > On backlight disable for AUX based panels set the brightness to 0 before > disabling the backlight. PWM based backlight also does set the > brightness to 0 before disable.
Both the commit message and the code comments have a lot of the *what* but are very thin on the *why*. Even if there's *zero* explanation of the *what*, it can be deduced from the code changes. But nothing can replace the *why*. Answering the *why* is the single most important thing a commit message *must* do. BR, Jani. > > Signed-off-by: Arun R Murthy <[email protected]> > --- > .../gpu/drm/i915/display/intel_dp_aux_backlight.c | 15 +++++++++++++-- > 1 file changed, 13 insertions(+), 2 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 a8d56ebf06a2..e4ce39c1eebb 100644 > --- a/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c > +++ b/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c > @@ -355,9 +355,14 @@ intel_dp_aux_hdr_disable_backlight(const struct > drm_connector_state *conn_state, > struct intel_connector *connector = > to_intel_connector(conn_state->connector); > struct intel_panel *panel = &connector->panel; > > - /* Nothing to do for AUX based backlight controls */ > - if (panel->backlight.edp.intel_cap.sdr_uses_aux) > + /* > + * Drive the DPCD brightness to 0 before tearing down the link / power > + * sequencer so the panel can blank emission gracefully. > + */ > + if (panel->backlight.edp.intel_cap.sdr_uses_aux) { > + intel_dp_aux_hdr_set_aux_backlight(conn_state, 0); > return; > + } > > /* Note we want the actual pwm_level to be 0, regardless of pwm_min */ > panel->backlight.pwm_funcs->disable(conn_state, > intel_backlight_invert_pwm_level(connector, 0)); > @@ -519,6 +524,12 @@ static void intel_dp_aux_vesa_disable_backlight(const > struct drm_connector_state > struct intel_panel *panel = &connector->panel; > struct intel_dp *intel_dp = enc_to_intel_dp(connector->encoder); > > + /* > + * Drive the DPCD brightness register to 0 before clearing BL_ENABLE or > + * dropping the panel power. > + */ > + drm_edp_backlight_set_level(&intel_dp->aux, > &panel->backlight.edp.vesa.info, 0); > + > drm_edp_backlight_disable(&intel_dp->aux, > &panel->backlight.edp.vesa.info); > > if (!(panel->backlight.edp.vesa.info.aux_enable || -- Jani Nikula, Intel
