Hi, On Sat, Apr 8, 2023 at 1:20 AM Nikita Travkin <nikita@xxxxxxx> wrote: > > This bridge doesn't actually implement HPD due to it being way too slow > but instead expects the panel driver to wait enough to assume HPD is > asserted. However some panels (such as the generic 'edp-panel') expect > the bridge to deal with the delay and pass maximum delay to the aux > instead. > > In order to support such panels, add a dummy implementation of wait > that would just sleep the maximum delay and assume no failure has > happened. > > Signed-off-by: Nikita Travkin <nikita@xxxxxxx> > --- > This was suggested in [1] to make sure DT users can be semantically > correct (not adding no-hpd when the line is actually there) while > still using a hard delay to be faster than waiting the long debounce > time. > > [1] - https://lore.kernel.org/all/CAD=FV=VR7sKsquE25eF7joc7gPApu-vqwduZzjE=wFCoXjMYnQ@xxxxxxxxxxxxxx/ > --- > drivers/gpu/drm/bridge/ti-sn65dsi86.c | 19 +++++++++++++++++++ > 1 file changed, 19 insertions(+) > > diff --git a/drivers/gpu/drm/bridge/ti-sn65dsi86.c b/drivers/gpu/drm/bridge/ti-sn65dsi86.c > index 7a748785c545..260cad1fd1da 100644 > --- a/drivers/gpu/drm/bridge/ti-sn65dsi86.c > +++ b/drivers/gpu/drm/bridge/ti-sn65dsi86.c > @@ -618,6 +618,24 @@ static ssize_t ti_sn_aux_transfer(struct drm_dp_aux *aux, > return len; > } > > +static int ti_sn_aux_wait_hpd_asserted(struct drm_dp_aux *aux, unsigned long wait_us) > +{ > + /* > + * The HPD in this chip is a bit useless (See comment in > + * ti_sn65dsi86_enable_comms) so if our driver is expected to wait > + * for HPD, we just assume it's asserted after the wait_us delay. > + * > + * In case we are asked to wait forever (wait_us=0) take conservative > + * 500ms delay. > + */ > + if (wait_us == 0) > + wait_us = 500000; > + > + usleep_range(wait_us, wait_us + 1000); > + > + return 0; > +} > + > static int ti_sn_aux_probe(struct auxiliary_device *adev, > const struct auxiliary_device_id *id) > { > @@ -627,6 +645,7 @@ static int ti_sn_aux_probe(struct auxiliary_device *adev, > pdata->aux.name = "ti-sn65dsi86-aux"; > pdata->aux.dev = &adev->dev; > pdata->aux.transfer = ti_sn_aux_transfer; > + pdata->aux.wait_hpd_asserted = ti_sn_aux_wait_hpd_asserted; This looks reasonable to me, but I think you only want this implementation if the "no-hpd" property _isn't_ present. In other words: if (!of_property_read_bool(np, "no-hpd")) pdata->aux.wait_hpd_asserted = ti_sn_aux_wait_hpd_asserted; Essentially: * If "no-hpd" is present in ti-sn65dsi86 then we'll assume that HPD is handled by the panel driver via a GPIO or a "no-hpd" there (which will cause the panel driver to wait the maximum duration). * If "no-hpd" isn't present in ti-sn65dsi86 then HPD is actually hooked up and thus the panel driver _won't_ handle it. Does that seem right? Presumably this should be explained by comments. -Doug
