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

[Mario Limonciello]

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.