Re: [PATCH v4] thunderbolt: Assert downstream port reset on shutdown

[Mika Westerberg <mika.westerberg@linux.intel.com>]

Hi,

On Thu, Jun 11, 2026 at 11:11:57AM +0530, Basavaraj Natikar wrote:
> On shutdown the connection manager tears down the router tree without
> signalling connected devices. A Thunderbolt 3 device directly connected
> to a USB4 host never receives a disconnect indication and during shutdown
> this can cause polling the dead link for up to 60 seconds. On some
> platforms this behavior leads to a warm reset instead of a shutdown due
> to this timeout.
> 
> Fix this by asserting PORT_CS_19.DPR on each connected downstream port
> before tearing down the router tree. This drives SBTX low (USB4 spec
> section 6.9), causing the device to detect SBRX low and transition to
> Uninitialized Unplugged state immediately.
> 
> Always do this on system shutdown/reboot by forcing host_reset in the
> PCI ->shutdown callback. On plain driver unload only do it when the host
> router was actually reset on load (host_reset=1), since in that case the
> tunnels are not preserved across reload anyway; with host_reset=0 the
> tunnels are kept alive across unload/reload so the links are left intact.
> Restrict the reset to Thunderbolt 3 devices.
> 
> Reviewed-by: Mario Limonciello (AMD) <superm1@kernel.org>
> Co-developed-by: Sanath S <Sanath.S@amd.com>
> Signed-off-by: Sanath S <Sanath.S@amd.com>
> Signed-off-by: Basavaraj Natikar <Basavaraj.Natikar@amd.com>

Applied to thunderbolt.git/next, thanks!