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Mathias Nyman baa3ebbad8 xhci: Limit time spent with xHC interrupts disabled during bus resume [ Upstream commit `bea5892d0e` ] 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> Signed-off-by: Sasha Levin <sashal@kernel.org>		History 2025-05-09 09:44:06 +02:00
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README

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.