Re: [Patch v2 2/2] thunderbolt: Teardown tunnels and reset downstream ports created by boot firmware

[Mario Limonciello]

On 12/12/2023 13:24, Mario Limonciello wrote:
> On 12/12/2023 13:16, Sanath S wrote:
> > Boot firmware might have created tunnels of its own. Since we cannot
> > be sure they are usable for us. Tear them down and reset the ports
> > to handle it as a new hotplug for USB3 routers.
> s/3/4/
>
> > Suggested-by: Mario Limonciello <mario.limonciello@xxxxxxx>
> > Signed-off-by: Sanath S <Sanath.S@xxxxxxx>
> > ---
> >   drivers/thunderbolt/tb.c | 11 +++++++++++
> >   1 file changed, 11 insertions(+)
> >
> > diff --git a/drivers/thunderbolt/tb.c b/drivers/thunderbolt/tb.c
> > index fd49f86e0353..febd0b6972e3 100644
> > --- a/drivers/thunderbolt/tb.c
> > +++ b/drivers/thunderbolt/tb.c
> > @@ -2598,6 +2598,17 @@ static int tb_start(struct tb *tb)
> >       tb_switch_tmu_enable(tb->root_switch);
> >       /* Full scan to discover devices added before the driver was 
> > loaded. */
> >       tb_scan_switch(tb->root_switch);
> > +    /*
> > +     * Boot firmware might have created tunnels of its own. Since we 
> > cannot
> > +     * be sure they are usable for us, Tear them down and reset the 
> > ports
> > +     * to handle it as new hotplug for USB4 routers.
> > +     */
> > +    if (tb_switch_is_usb4(tb->root_switch)) {
> > +        tb_switch_discover_tunnels(tb->root_switch,
> > +                       &tcm->tunnel_list, false);
> > +        tcm->hotplug_active = true;
> > +        return tb_switch_reset_ports(tb->root_switch);
> > +    }
> >       /* Find out tunnels created by the boot firmware */
> >       tb_discover_tunnels(tb);
> >       /* Add DP resources from the DP tunnels created by the boot 
> > firmware */
>
> Doesn't this cause the following to not run and thus break hotplug?
>
> tcm->hotplug_active = true;
>
>
> I think it would be better to do this like this flow:
>
>      if (tb_switch_is_usb4(tb->root_switch)) {
>          tb_switch_discover_tunnels(tb->root_switch,
>                         &tcm->tunnel_list, false);
>          tcm->hotplug_active = true;
>          ret = tb_switch_reset_ports(tb->root_switch);
>          if (ret)
>              return ret;
>      } else {
>          /* keep existing tunnel flow */
>      }
>
>      tcm->hotplug_active = true;
>
>      return 0;
>
> That makes it crystal clear that hotplug isn't enabled until it's done 
> being setup, which means either getting the existing tunnels or doing 
> the reset.

My apologies I completely missed replacement call even though I pasted it.

Besides the s/3/4 this looks fine to me.

Reviewed-by: Mario Limonciello <mario.limonciello@xxxxxxx>