commit 9aa09d2f8f4bc440d6db1c3414d4009642875240
author Karsten Wiese <fzu@wemgehoertderstaat.de> Sun Feb 08 16:07:58 2009 -0800
committer Greg Kroah-Hartman <gregkh@suse.de> Fri Feb 27 14:40:50 2009 -0800
tree 11b8735a5ddb24fcb4b810b9af3959a8aae6a1ae
parent 9a6e184c804b33a2c2ea974efcd3c9798d30cb39

USB: EHCI: slow down ITD reuse

Currently ITDs are immediately recycled whenever their URB completes.
However, EHCI hardware can sometimes remember some ITD state.  This
means that when the ITD is reused before end-of-frame it may sometimes
cause the hardware to reference bogus state.

This patch defers reusing such ITDs by moving them into a new ehci member
cached_itd_list. ITDs resting in cached_itd_list are moved back into their
stream's free_list once scan_periodic() detects that the active frame has
elapsed.

This makes the snd_usb_us122l driver (in kernel since .28) work right
when it's hooked up through EHCI.

[ dbrownell@users.sourceforge.net: comment fixups ]

Signed-off-by: Karsten Wiese <fzu@wemgehoertderstaat.de>
Tested-by: Philippe Carriere <philippe-f.carriere@wanadoo.fr>
Tested-by: Federico Briata <federicobriata@gmail.com>
Cc: stable <stable@kernel.org>
Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>