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SubjectRe: [Patch v2 2/2] thunderbolt: Teardown tunnels and reset downstream ports created by boot firmware
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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@amd.com>
> Signed-off-by: Sanath S <Sanath.S@amd.com>
> ---
> 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.

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