From: Paolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it>
Date: Thu, 7 Dec 2006 01:14:07 +0000 (+0100)
Subject: [PATCH] x86-64: Make x86_64 udelay() round up instead of down.
X-Git-Tag: v2.6.20-rc1~145^2^2~8^2~85
X-Git-Url: https://err.no/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=b9a8d94a47f8a41766f6f7944adfb1d641349903;p=linux-2.6

[PATCH] x86-64: Make x86_64 udelay() round up instead of down.

Port two patches from i386 to x86_64 delay.c to make sure all rounding is done
upward instead of downward.

There is no sign in commit messages that the mismatch was done on purpose, and
"delay() guarantees sleeping at least for the specified time" is still a valid
rule IMHO.

The original x86 patches are both from pre-GIT era, i.e.:

"[PATCH] round up  in __udelay()" in commit
54c7e1f5cc6771ff644d7bc21a2b829308bd126f

"[PATCH] add 1 in __const_udelay()" in commit
42c77a9801b8877d8b90f65f75db758822a0bccc

(both commits are from converted BK repository to x86_64).

AK: fixed gcc warning

linux/arch/x86_64/lib/delay.c:43: warning: suggest parentheses around + or - inside shift
(did this actually work?)

Signed-off-by: Paolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it>
Signed-off-by: Andi Kleen <ak@suse.de>
---

diff --git a/arch/x86_64/lib/delay.c b/arch/x86_64/lib/delay.c
index 50be90975d..2dbebd3083 100644
--- a/arch/x86_64/lib/delay.c
+++ b/arch/x86_64/lib/delay.c
@@ -40,13 +40,13 @@ EXPORT_SYMBOL(__delay);
 
 inline void __const_udelay(unsigned long xloops)
 {
-	__delay((xloops * HZ * cpu_data[raw_smp_processor_id()].loops_per_jiffy) >> 32);
+	__delay(((xloops * HZ * cpu_data[raw_smp_processor_id()].loops_per_jiffy) >> 32) + 1);
 }
 EXPORT_SYMBOL(__const_udelay);
 
 void __udelay(unsigned long usecs)
 {
-	__const_udelay(usecs * 0x000010c6);  /* 2**32 / 1000000 */
+	__const_udelay(usecs * 0x000010c7);  /* 2**32 / 1000000 (rounded up) */
 }
 EXPORT_SYMBOL(__udelay);
 
diff --git a/include/asm-x86_64/delay.h b/include/asm-x86_64/delay.h
index 65f64acc53..40146f611c 100644
--- a/include/asm-x86_64/delay.h
+++ b/include/asm-x86_64/delay.h
@@ -16,7 +16,7 @@ extern void __const_udelay(unsigned long usecs);
 extern void __delay(unsigned long loops);
 
 #define udelay(n) (__builtin_constant_p(n) ? \
-	((n) > 20000 ? __bad_udelay() : __const_udelay((n) * 0x10c6ul)) : \
+	((n) > 20000 ? __bad_udelay() : __const_udelay((n) * 0x10c7ul)) : \
 	__udelay(n))
 
 #define ndelay(n) (__builtin_constant_p(n) ? \