c938e65768
commit 0b60557230adfdeb8164e0b342ac9cd469a75759 upstream.
When MSI is used by the ehci-hcd driver, it can cause lost interrupts which
results in EHCI only continuing to work due to a polling fallback. But the
reliance of polling drastically reduces performance of any I/O through EHCI.
Interrupts are lost as the EHCI interrupt handler does not safely handle
edge-triggered interrupts. It fails to ensure all interrupt status bits are
cleared, which works with level-triggered interrupts but not the
edge-triggered interrupts typical from using MSI.
To fix this problem, check if the driver may have raced with the hardware
setting additional interrupt status bits and clear status until it is in a
stable state.
Fixes: 306c54d0edb6 ("usb: hcd: Try MSI interrupts on PCI devices")
Tested-by: Laurence Oberman <loberman@redhat.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Acked-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: David Jeffery <djeffery@redhat.com>
Link: https://lore.kernel.org/r/20210715213744.GA44506@redhat
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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.