Hi Doug,
> On Wed, Mar 30, 2022 at 9:04 AM Sankeerth Billakanti
> <quic_sbillaka@xxxxxxxxxxx> wrote:
> >
> > Some eDP sinks or platform boards will not support hpd.
> > This patch adds support for those cases.
>
> You could say more, like:
>
> If we're not using HPD then _both_ the panel node and the eDP controller
> node will have "no-hpd". This tells the eDP panel code to hardcode the
> maximum possible delay for a panel to power up and tells the eDP driver that
> it should continue to do transfers even if HPD isn't asserted.
>
Okay. I will add it
>
> > Signed-off-by: Sankeerth Billakanti <quic_sbillaka@xxxxxxxxxxx>
> > ---
> > drivers/gpu/drm/msm/dp/dp_catalog.c | 15 ++++++++++++---
> > 1 file changed, 12 insertions(+), 3 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/msm/dp/dp_catalog.c
> > b/drivers/gpu/drm/msm/dp/dp_catalog.c
> > index 1809ce2..8f1fc71 100644
> > --- a/drivers/gpu/drm/msm/dp/dp_catalog.c
> > +++ b/drivers/gpu/drm/msm/dp/dp_catalog.c
> > @@ -244,10 +244,17 @@ void dp_catalog_aux_update_cfg(struct
> dp_catalog
> > *dp_catalog)
> >
> > int dp_catalog_aux_wait_for_hpd_connect_state(struct dp_catalog
> > *dp_catalog) {
> > - u32 state;
> > + u32 state, hpd_en;
> > struct dp_catalog_private *catalog = container_of(dp_catalog,
> > struct dp_catalog_private,
> > dp_catalog);
> >
> > + hpd_en = dp_read_aux(catalog, REG_DP_DP_HPD_CTRL);
> > + hpd_en &= DP_DP_HPD_CTRL_HPD_EN;
> > +
> > + /* no-hpd case */
> > + if (!hpd_en)
> > + return 0;
> > +
> > /* poll for hpd connected status every 2ms and timeout after 500ms */
> > return readl_poll_timeout(catalog->io->dp_controller.aux.base +
> > REG_DP_DP_HPD_INT_STATUS, @@ -586,8
> > +593,10 @@ void dp_catalog_ctrl_hpd_config(struct dp_catalog
> *dp_catalog)
> > reftimer |= DP_DP_HPD_REFTIMER_ENABLE;
> > dp_write_aux(catalog, REG_DP_DP_HPD_REFTIMER, reftimer);
> >
> > - /* Enable HPD */
> > - dp_write_aux(catalog, REG_DP_DP_HPD_CTRL,
> DP_DP_HPD_CTRL_HPD_EN);
> > + /* Enable HPD if supported*/
> > + if (!of_property_read_bool(catalog->dev->of_node, "no-hpd"))
>
> I don't think this is a particularly lightweight operation. It's literally iterating
> through all of our device tree properties and doing string compares on them.
> ...but this function is called somewhat often, isn't it? It feels like the kind of
> thing that should happen at probe time and be stored in a boolean.
>
> ...and then you can use that same boolean in
> dp_catalog_aux_wait_for_hpd_connect_state() rather than reading the
> register value, right?
>
It is called twice for DP. Once while booting through a thread scheduled from kms_obj_init
and when resuming from PM suspend.
With aux_bus addition, this function will be called thrice for eDP. Once during bootup with
aux_bus, then from scheduled event from kms_obj_init and pm resume like DP.
I will check if we can use a no-hpd Boolean flag instead.
>
> -Doug
Thank you,
Sankeerth
