thunderbolt: Assert downstream port reset on shutdown

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>
Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>

0 files changed, 0 insertions, 0 deletions