From: Martin Michlmayr <tbm@cyrius.com>
Date: Fri, 28 Sep 2012 00:18:58 +0000 (+1000)
Subject: drivers/scsi/atp870u.c: fix bad use of udelay
X-Git-Tag: next-20120928~1^2~382
X-Git-Url: https://git.karo-electronics.de/?a=commitdiff_plain;h=a42ded2cb54f3cbd26ab16b7f9f40c70e5780a7e;p=karo-tx-linux.git

drivers/scsi/atp870u.c: fix bad use of udelay

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.

[jn: adding context]
Signed-off-by: Martin Michlmayr <tbm@cyrius.com>
Signed-off-by: Jonathan Nieder <jrnieder@gmail.com>
Cc: James Bottomley <James.Bottomley@HansenPartnership.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

diff --git a/drivers/scsi/atp870u.c b/drivers/scsi/atp870u.c
index 68ce08552f69..a540162ac59c 100644
--- 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);