From 0f6d93aa9d96cc9022b51bd10d462b03296be146 Mon Sep 17 00:00:00 2001 From: Martin Michlmayr Date: Thu, 4 Oct 2012 17:11:25 -0700 Subject: [PATCH] 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. [jrnieder@gmail.com: adding context] Signed-off-by: Martin Michlmayr Signed-off-by: Jonathan Nieder Cc: James Bottomley Cc: Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- 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 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); -- 2.20.1