usb: ehci: Prevent missed ehci interrupts with edge-triggered MSI
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: 306c54d0 ("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>
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