Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754599Ab2JNOmn (ORCPT ); Sun, 14 Oct 2012 10:42:43 -0400 Received: from shadbolt.e.decadent.org.uk ([88.96.1.126]:46353 "EHLO shadbolt.e.decadent.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754586Ab2JNOmk (ORCPT ); Sun, 14 Oct 2012 10:42:40 -0400 Message-Id: <20121014143547.834371336@decadent.org.uk> User-Agent: quilt/0.60-1 Date: Sun, 14 Oct 2012 15:37:17 +0100 From: Ben Hutchings To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: akpm@linux-foundation.org, alan@lxorguk.ukuu.org.uk, Martin Michlmayr , Jonathan Nieder , James Bottomley , Linus Torvalds Subject: [ 104/147] drivers/scsi/atp870u.c: fix bad use of udelay In-Reply-To: <20121014143533.742627615@decadent.org.uk> X-SA-Exim-Connect-IP: 77.75.106.1 X-SA-Exim-Mail-From: ben@decadent.org.uk X-SA-Exim-Scanned: No (on shadbolt.decadent.org.uk); SAEximRunCond expanded to false Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2277 Lines: 65 3.2-stable review patch. If anyone has any objections, please let me know. ------------------ From: Martin Michlmayr 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. [jrnieder@gmail.com: adding context] Signed-off-by: Martin Michlmayr Signed-off-by: Jonathan Nieder Cc: James Bottomley Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Ben Hutchings --- drivers/scsi/atp870u.c | 11 ++++++++++- 1 file changed, 10 insertions(+), 1 deletion(-) diff --git a/drivers/scsi/atp870u.c b/drivers/scsi/atp870u.c index 68ce085..a540162 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); -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/