USB: EHCI: fix divide-by-zero bug

This patch (as1164) fixes a bug in the EHCI scheduler.  The interval
value it uses is already in linear format, not logarithmically coded.
The existing code can sometimes crash the system by trying to divide
by zero.

Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Cc: David Brownell <david-b@pacbell.net>
Cc: Stable <stable@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

1 files changed, 2 insertions, 2 deletions

diff --git a/drivers/usb/host/ehci-sched.c b/drivers/usb/host/ehci-sched.c
index 4a0c5a78b2ed..a081ee65bde6 100644
--- a/drivers/usb/host/ehci-sched.c
+++ b/drivers/usb/host/ehci-sched.c
@@ -918,7 +918,7 @@ iso_stream_init (
                  */
                 stream->usecs = HS_USECS_ISO (maxp);
                 bandwidth = stream->usecs * 8;
-                bandwidth /= 1 << (interval - 1);
+                bandwidth /= interval;
 
         } else {
                 u32             addr;
@@ -951,7 +951,7 @@ iso_stream_init (
                 } else
                         stream->raw_mask = smask_out [hs_transfers - 1];
                 bandwidth = stream->usecs + stream->c_usecs;
-                bandwidth /= 1 << (interval + 2);
+                bandwidth /= interval << 3;
 
                 /* stream->splits gets created from raw_mask later */
                 stream->address = cpu_to_hc32(ehci, addr);