[PATCH] drm/msm/dp: move add fail safe mode to dp_connector_get_mode()

[Stephen Boyd]

Quoting Kuogee Hsieh (2022-04-22 16:45:23)
> Current DP driver implementation has adding safe mode done at
> dp_hpd_plug_handle() which is expected to be executed under event
> thread context.
>
> However there is possible circular locking happen (see blow stack trace)
> after edp driver call dp_hpd_plug_handle() from dp_bridge_enable() which
> is executed under drm_thread context.
>
> To break this circular locking, this patch have safe mode added at
> dp_connector_get_mode() which is executed under drm thread context.
> Therefore no lock acquired required for &dev->mode_config.mutex while
> adding fail safe mode since it has been hold by drm thread already.

Reported-by: Douglas Anderson <dianders at chromium.org>
Fixes: 8b2c181e3dcf ("drm/msm/dp: add fail safe mode outside of
event_mutex context")
Reviewed-by: Stephen Boyd <swboyd at chromium.org>