This is a note to let you know that I've just added the patch titled
drivers/scsi/atp870u.c: fix bad use of udelay
to the 3.6-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
drivers-scsi-atp870u.c-fix-bad-use-of-udelay.patch
and it can be found in the queue-3.6 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <[email protected]> know about it.
>From 0f6d93aa9d96cc9022b51bd10d462b03296be146 Mon Sep 17 00:00:00 2001
From: Martin Michlmayr <[email protected]>
Date: Thu, 4 Oct 2012 17:11:25 -0700
Subject: drivers/scsi/atp870u.c: fix bad use of udelay
From: Martin Michlmayr <[email protected]>
commit 0f6d93aa9d96cc9022b51bd10d462b03296be146 upstream.
The ACARD driver calls udelay() with a value > 2000, which leads to to
the following compilation error on ARM:
ERROR: "__bad_udelay" [drivers/scsi/atp870u.ko] undefined!
make[1]: *** [__modpost] Error 1
This is because udelay is defined on ARM, roughly speaking, as
#define udelay(n) ((n) > 2000 ? __bad_udelay() : \
__const_udelay((n) * ((2199023U*HZ)>>11)))
The argument to __const_udelay is the number of jiffies to wait divided
by 4, but this does not work unless the multiplication does not
overflow, and that is what the build error is designed to prevent. The
intended behavior can be achieved by using mdelay to call udelay
multiple times in a loop.
[[email protected]: adding context]
Signed-off-by: Martin Michlmayr <[email protected]>
Signed-off-by: Jonathan Nieder <[email protected]>
Cc: James Bottomley <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
---
drivers/scsi/atp870u.c | 11 ++++++++++-
1 file changed, 10 insertions(+), 1 deletion(-)
--- a/drivers/scsi/atp870u.c
+++ b/drivers/scsi/atp870u.c
@@ -1173,7 +1173,16 @@ wait_io1:
outw(val, tmport);
outb(2, 0x80);
TCM_SYNC:
- udelay(0x800);
+ /*
+ * The funny division into multiple delays is to accomodate
+ * arches like ARM where udelay() multiplies its argument by
+ * a large number to initialize a loop counter. To avoid
+ * overflow, the maximum supported udelay is 2000 microseconds.
+ *
+ * XXX it would be more polite to find a way to use msleep()
+ */
+ mdelay(2);
+ udelay(48);
if ((inb(tmport) & 0x80) == 0x00) { /* bsy ? */
outw(0, tmport--);
outb(0, tmport);
Patches currently in stable-queue which might be from [email protected] are
queue-3.6/drivers-scsi-atp870u.c-fix-bad-use-of-udelay.patch
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