[PATCH] drm/msm/dp: support setting the DP subconnector type

[Stephen Boyd]

Quoting Dmitry Baryshkov (2023-09-03 15:24:32)
> diff --git a/drivers/gpu/drm/msm/dp/dp_panel.c b/drivers/gpu/drm/msm/dp/dp_panel.c
> index 97ba41593820..1cb54f26f5aa 100644
> --- a/drivers/gpu/drm/msm/dp/dp_panel.c
> +++ b/drivers/gpu/drm/msm/dp/dp_panel.c
> @@ -162,6 +162,11 @@ int dp_panel_read_sink_caps(struct dp_panel *dp_panel,
>                 }
>         }
>
> +       rc = drm_dp_read_downstream_info(panel->aux, dp_panel->dpcd,
> +                                        dp_panel->downstream_ports);
> +       if (rc)
> +               return rc;

I haven't been able to test it yet, but I think with an apple dongle
we'll never populate the 'downstream_ports' member if the HDMI cable is
not connected when this runs. That's because this function bails out
early before trying to read the downstream ports when there isn't a
sink. Perhaps we need to read it again when an hpd_irq comes in, or we
need to read it before bailing out from here?