Re: [PATCH v11 1/4] drm/msm/dp: do not initialize phy until plugin interrupt received

[Kuogee Hsieh]

On 1/13/2022 1:52 PM, Stephen Boyd wrote:
> Quoting Kuogee Hsieh (2022-01-13 12:44:16)
> > On 1/13/2022 11:47 AM, Stephen Boyd wrote:
> > > Quoting Kuogee Hsieh (2022-01-13 09:51:42)
> > > > On 1/12/2022 8:13 PM, Stephen Boyd wrote:
> > > > > > > > -       if (dp->usbpd->orientation == ORIENTATION_CC2)
> > > > > > > > -               flip = true;
> > > > > > > > +       dp_power_init(dp->power, false);
> > > > > > > > +       dp_ctrl_reset_irq_ctrl(dp->ctrl, true);
> > > > > > > > +
> > > > > > > > +       /*
> > > > > > > > +        * eDP is the embedded primary display and has its own phy
> > > > > > > > +        * initialize phy immediately
> > > > > > > Question still stands why we can't wait for hpd high from the eDP panel.
> > > > > > > Also, I think "has its own phy" means that it's not part of a combo
> > > > > > > USB+DP phy? Can you please clarify?
> > Correct, eDP has its dedicated phy which is not part of combo phy.
> Why does that mean we can't wait for hpd high from the eDP panel?

Sorry, missed this one.

Yes, it can wait for hpd high.

Since it always presented, I just think it is better to show display 
sooner not later until hdp high.

you like it to wait until hpd high?

> > > > > > > > +        */
> > > > > > > > +       if (dp->dp_display.connector_type == DRM_MODE_CONNECTOR_eDP)
> > > > > > > > +               dp_display_host_phy_init(dp);
> > > > > > > >
> > > > > > > > -       dp_power_init(dp->power, flip);
> > > > > > > > -       dp_ctrl_host_init(dp->ctrl, flip, reset);
> > > > > > > >             dp_aux_init(dp->aux);
> > > > > > > >             dp->core_initialized = true;
> > > > > > > >      }
> > > > > > > > @@ -1306,20 +1330,23 @@ static int dp_pm_resume(struct device *dev)
> > > > > > > >             dp->hpd_state = ST_DISCONNECTED;
> > > > > > > >
> > > > > > > >             /* turn on dp ctrl/phy */
> > > > > > > > -       dp_display_host_init(dp, true);
> > > > > > > > +       dp_display_host_init(dp);
> > > > > > > >
> > > > > > > >             dp_catalog_ctrl_hpd_config(dp->catalog);
> > > > > > > >
> > > > > > > > -       /*
> > > > > > > > -        * set sink to normal operation mode -- D0
> > > > > > > > -        * before dpcd read
> > > > > > > > -        */
> > > > > > > > -       dp_link_psm_config(dp->link, &dp->panel->link_info, false);
> > > > > > > >
> > > > > > > >             if (dp_catalog_link_is_connected(dp->catalog)) {
> > > > > > > > +               /*
> > > > > > > > +                * set sink to normal operation mode -- D0
> > > > > > > > +                * before dpcd read
> > > > > > > > +                */
> > > > > > > > +               dp_display_host_phy_init(dp);
> > > > > > > > +               dp_link_psm_config(dp->link, &dp->panel->link_info, false);
> > > > > > > >                     sink_count = drm_dp_read_sink_count(dp->aux);
> > > > > > > >                     if (sink_count < 0)
> > > > > > > >                             sink_count = 0;
> > > > > > > > +
> > > > > > > > +               dp_display_host_phy_exit(dp);
> > > > > > > Why is the phy exited on resume when the link is still connected? Is
> > > > > > > this supposed to be done only when the sink_count is 0? And how does
> > > > > > > this interact with eDP where the phy is initialized by the call to
> > > > > > > dp_display_host_init() earlier in this function.
> > At beginning of dp_pm_resume bot core_initialized and phy_initialized
> > should be off.
> >
> > However at the case of dongle still connected to DUT, we have to read
> > dongle dpcd to decided any hdmi connect to dongle (sink_count != 0). in
> > this case, we have to turn on phy to perform dpcd read and  turn off phy
> > after read so the following plugged-in interrupt can be handled correctly.
> That looks like a lot of wasted work. Why can't we turn on the core,
> turn on the phy, check if it's connected, and then turn off the phy if
> it isn't? At the least, please put a comment above this phy_exit() call
> indicating that we'll turn the phy back on while processing a plugged in
> interrupt.