USB: EHCI: fix bug in scheduling periodic split transfers
authorAlan Stern <stern@rowland.harvard.edu>
Wed, 30 Jan 2013 21:36:40 +0000 (16:36 -0500)
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Thu, 31 Jan 2013 09:14:48 +0000 (10:14 +0100)
commit3e619d04159be54b3daa0b7036b0ce9e067f4b5d
treeacc77a30daea819c03bcb9edabedf30a38a661d0
parentb09a61cc0bc2a7151f4ab652489e85253d5d0175
USB: EHCI: fix bug in scheduling periodic split transfers

This patch (as1654) fixes a very old bug in ehci-hcd, connected with
scheduling of periodic split transfers.  The calculations for
full/low-speed bus usage are all carried out after the correction for
bit-stuffing has been applied, but the values in the max_tt_usecs
array assume it hasn't been.  The array should allow for allocation of
up to 90% of the bus capacity, which is 900 us, not 780 us.

The symptom caused by this bug is that any isochronous transfer to a
full-speed device with a maxpacket size larger than about 980 bytes is
always rejected with a -ENOSPC error.

Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
drivers/usb/host/ehci-sched.c