On Wed, Sep 15, 2021 at 1:47 AM Jani Nikula <jani.nikula@xxxxxxxxxxxxxxx> wrote: > > On Tue, 14 Sep 2021, Vasily Khoruzhick <anarsoul@xxxxxxxxx> wrote: > > On Tue, Sep 14, 2021 at 3:31 PM Jani Nikula <jani.nikula@xxxxxxxxxxxxxxx> wrote: > >> > >> On Tue, 14 Sep 2021, Lyude Paul <lyude@xxxxxxxxxx> wrote: > >> > On Tue, 2021-09-14 at 12:09 +0300, Jani Nikula wrote: > >> >> On Mon, 13 Sep 2021, Vasily Khoruzhick <anarsoul@xxxxxxxxx> wrote: > >> >> > Panel in my Dell XPS 7590, that uses Intel's HDR backlight interface to > >> >> > control brightness, apparently needs a delay before setting brightness > >> >> > after power on. Without this delay the panel does accept the setting > >> >> > and may come up with some arbitrary brightness (sometimes it's too dark, > >> >> > sometimes it's too bright, I wasn't able to find a system). > >> >> > > >> >> > I don't have access to the spec, so I'm not sure if it's expected > >> >> > behavior or a quirk for particular device. > >> >> > > >> >> > Delay was chosen by experiment: it works with 100ms, but fails with > >> >> > anything lower than 75ms. > >> >> > >> >> Looks like we don't respect the panel delays for DPCD backlight. The > >> >> values are used for setting up the panel power sequencer, and thus PWM > >> >> based backlight, but we should probably use the delays in DPCD backlight > >> >> code too. > >> > > >> > This makes sense to me, you're referring to the panel delays in the VBT > >> > correct? > >> > >> Yes. See pps_init_delays() and intel_pps_backlight_on(). The delays > >> aren't applied to DPCD backlight, I think it would make sense if they > >> were. > > > > I guess it explains why it usually stops working after suspend. > > Probably BIOS doesn't re-init the power sequencer on resume. > > The point is, the DPCD backlight isn't driven via the power sequencer, > while the PWM pin would be. > > Please file a bug at [1], and attach /sys/kernel/debug/dri/0/i915_vbt as > well as dmesg from boot with drm.debug=14 module parameter set. Done, see https://gitlab.freedesktop.org/drm/intel/-/issues/4170 > Thanks, > Jani. > > > [1] https://gitlab.freedesktop.org/drm/intel/issues/new > > > > > > >> BR, > >> Jani. > >> > >> > > >> >> > >> >> BR, > >> >> Jani. > >> >> > >> >> > >> >> > > >> >> > Signed-off-by: Vasily Khoruzhick <anarsoul@xxxxxxxxx> > >> >> > --- > >> >> > drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c | 4 ++++ > >> >> > 1 file changed, 4 insertions(+) > >> >> > > >> >> > 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 4f8337c7fd2e..c4f35e1b5870 100644 > >> >> > --- a/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c > >> >> > +++ b/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c > >> >> > @@ -210,6 +210,10 @@ intel_dp_aux_hdr_enable_backlight(const struct > >> >> > intel_crtc_state *crtc_state, > >> >> > > >> >> > ctrl = old_ctrl; > >> >> > if (panel->backlight.edp.intel.sdr_uses_aux) { > >> >> > + /* Wait 100ms to ensure that panel is ready otherwise it > >> >> > may not > >> >> > + * set chosen backlight level > >> >> > + */ > >> >> > + msleep(100); > >> >> > ctrl |= INTEL_EDP_HDR_TCON_BRIGHTNESS_AUX_ENABLE; > >> >> > intel_dp_aux_hdr_set_aux_backlight(conn_state, level); > >> >> > } else { > >> >> > >> > >> -- > >> Jani Nikula, Intel Open Source Graphics Center > > -- > Jani Nikula, Intel Open Source Graphics Center
