Bluetooth: Properly disable remote wakeup for MT7922/MT7925 on Ryzen platform

It is reported that a remote wakeup could cause MT7922/MT7925's btusb
interface completely unresponsive. Resetting the xHCI root hub doesn't
help at all, and recovering from such a state needs a power cycle.

All reports seen to be relevant to Ryzen-based laptops. These NICs are
usually used as OEM components thanks to some sort of reference designs.
Their popularity on other platforms is unclear. While there is still a
chance that the quirk may exist on other platforms, be cautious and only
apply the quirk to direct children of Ryzen platforms's root hubs for
the time being. In most cases the root hub is on the SoC or PCH, which
needs the quirk. Unfortunately, this can't distinguish root hubs on PCIe
add-in cards. Such roughness should be acceptable, as PCIe USB
controller add-in cards are less commonly used nowadays. On the other
hand, applying the quirk doesn't hurt any functionalities either, as the
device can still be used as a wakeup source if desired. Theoretically,
we could retrieve the root hub's PCI vendor ID with some hierarchy
magic, but that's too intrusive...

Meanwhile, though device_set_wakeup_capable(false) is the correct fix
for other NICs with fake remote wakeup capabilities, doing so for
MT7922/MT7925 effectively prevents it from being used as wakeup
sources as per userspace requests. Hence, return -EBUSY on runtime
suspend to prevent the interface from being autosuspended while it's
still opened, which has the same effect as
device_set_wakeup_capable(false), since disabling remote wakeup simply
causes the USB core to gate runtime autosuspend as well due to
needs_remote_wakeup == 1. The interface can be safely autosuspended as
long as remote wakeup is disabled, i.e., after closing the HCI device.

Specifically, the interface may still take the advantage of remote
wakeup in order to wake up the system from sleep if userspace has
enabled it as a wakeup source.

Fixes: e31d761628ad ("Bluetooth: btmtk: Disable remote wakeup for MT7922/MT7925")
Tested-by: Rafael Passos <rafael@rcpassos.me>
Signed-off-by: Rong Zhang <i@rong.moe>
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>

0 files changed, 0 insertions, 0 deletions