[PATCH v3 16/17] platform/chrome: cros_ec_typec: Support DP muxing

[Stephen Boyd]

Quoting Tzung-Bi Shih (2024-08-22 07:37:05)
> On Mon, Aug 19, 2024 at 03:38:30PM -0700, Stephen Boyd wrote:
> > @@ -671,6 +674,20 @@ static int cros_typec_configure_mux(struct cros_typec_data *typec, int port_num,
> >       if (port->mux_flags == resp.flags && port->role == pd_ctrl->role)
> >               return 0;
> >
> > +     dp_enabled = resp.flags & USB_PD_MUX_DP_ENABLED;
> > +     hpd_asserted = resp.flags & USB_PD_MUX_HPD_LVL;
> > +     /*
> > +      * Assume the first port to have HPD asserted is the one muxed to DP
> > +      * (i.e. active_port). When there's only one port this delays setting
> > +      * the active_port until HPD is asserted, but before that the
> > +      * drm_connector looks disconnected so active_port doesn't need to be
> > +      * set.
> > +      */
> > +     if (dp_bridge && hpd_asserted && !dp_bridge->active_port)
> > +             dp_bridge->active_port = port;
> > +
> > +     is_active_port = !dp_bridge || dp_bridge->active_port == port;
>
> Why `!dp_bridge`?  When will `dp_bridge` be NULL?

I'll add a comment.

'dp_bridge' is NULL when this driver is running on non-DT platforms,
i.e. ACPI, or there isn't a graph/ports node for this device. The latter
could happen if there's some AP controlled piece of hardware that is a
typec switch, connected directly to a usb-c-connector. This is the case
on Kukui where we send the DP lanes directly to the usb-c-connector.