xhci: Fix errors in the running total calculations in the TRB math
commit5807795bd4dececdf553719cc02869e633395787
authorPaul Zimmerman <Paul.Zimmerman@synopsys.com>
Sat, 12 Feb 2011 22:07:20 +0000 (12 14:07 -0800)
committerSarah Sharp <sarah.a.sharp@linux.intel.com>
Sun, 20 Feb 2011 15:01:27 +0000 (20 07:01 -0800)
treed200e995de9dffbc6e6e44a8da4fcdc5f37a94aa
parenta2490187011cc2263117626615a581927d19f1d3
xhci: Fix errors in the running total calculations in the TRB math

Calculations like

running_total = TRB_MAX_BUFF_SIZE -
(sg_dma_address(sg) & (TRB_MAX_BUFF_SIZE - 1));
if (running_total != 0)
num_trbs++;

are incorrect, because running_total can never be zero, so the if()
expression will never be true. I think the intention was that
running_total be in the range of 0 to TRB_MAX_BUFF_SIZE-1, not 1
to TRB_MAX_BUFF_SIZE. So adding a

running_total &= TRB_MAX_BUFF_SIZE - 1;

fixes the problem.

This patch should be queued for stable kernels back to 2.6.31.

Signed-off-by: Paul Zimmerman <paulz@synopsys.com>
Signed-off-by: Sarah Sharp <sarah.a.sharp@linux.intel.com>
Cc: stable@kernel.org
drivers/usb/host/xhci-ring.c