xhci: Limit time spent with xHC interrupts disabled during bus resume

Current xhci bus resume implementation prevents xHC host from generating
interrupts during high-speed USB 2 and super-speed USB 3 bus resume.

Only reason to disable interrupts during bus resume would be to prevent
the interrupt handler from interfering with the resume process of USB 2
ports.

Host initiated resume of USB 2 ports is done in two stages.

The xhci driver first transitions the port from 'U3' to 'Resume' state,
then wait in Resume for 20ms, and finally moves port to U0 state.
xhci driver can't prevent interrupts by keeping the xhci spinlock
due to this 20ms sleep.

Limit interrupt disabling to the USB 2 port resume case only.
resuming USB 2 ports in bus resume is only done in special cases where
USB 2 ports had to be forced to suspend during bus suspend.

The current way of preventing interrupts by clearing the 'Interrupt
Enable' (INTE) bit in USBCMD register won't prevent the Interrupter
registers 'Interrupt Pending' (IP), 'Event Handler Busy' (EHB) and
USBSTS register Event Interrupt (EINT) bits from being set.

New interrupts can't be issued before those bits are properly clered.

Disable interrupts by clearing the interrupter register 'Interrupt
Enable' (IE) bit instead. This way IP, EHB and INTE won't be set
before IE is enabled again and a new interrupt is triggered.

Reported-by: Devyn Liu <liudingyuan@huawei.com>
Closes: https://lore.kernel.org/linux-usb/b1a9e2d51b4d4ff7a304f77c5be8164e@huawei.com/
Cc: stable@vger.kernel.org
Tested-by: Devyn Liu <liudingyuan@huawei.com>
Signed-off-by: Mathias Nyman <mathias.nyman@linux.intel.com>
Link: https://lore.kernel.org/r/20250410151828.2868740-6-mathias.nyman@linux.intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

0 files changed, 0 insertions, 0 deletions