USB: EHCI: fix divide-by-zero bug

commit 372dd6e8ed924e876f3beb598721e813ad7fa323 upstream.

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/drivers/usb/host/ehci-sched.c b/drivers/usb/host/ehci-sched.c
index 4a0c5a7..a081ee6 100644 (file)
--- 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);