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USB: EHCI: use hrtimer for interrupt QH unlink

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This patch (as1577) adds hrtimer support for unlinking interrupt QHs
in ehci-hcd.  The current code relies on a fixed delay of either 2 or
55 us, which is not always adequate and in any case is totally bogus.
Thanks to internal caching, the EHCI hardware may continue to access
an interrupt QH for more than a millisecond after it has been unlinked.

In fact, the EHCI spec doesn't say how long to wait before using an
unlinked interrupt QH.  The patch sets the delay to 9 microframes
minimum, which ought to be adequate.

Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Alan Stern 2012-07-11 11:22:26 -04:00 • committed by Greg Kroah-Hartman
commit df2022553d
5 changed files with 94 additions and 28 deletions
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