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authorRussell King <rmk+kernel@arm.linux.org.uk>2011-01-10 23:55:59 +0000
committerRussell King <rmk+kernel@arm.linux.org.uk>2011-01-10 23:55:59 +0000
commit56949d414acd30353fdba4b64876a0a7953a7b77 (patch)
tree7fb58dd19c6ab12480cb82f8b8a2b9141da1d905 /arch/arm/lib
parent9e9bc9736756f25d6c47b4eba0ebf25b20a6f153 (diff)
downloadlinux-linaro-stable-56949d414acd30353fdba4b64876a0a7953a7b77.tar.gz
ARM: udelay: prevent math rounding resulting in short udelays
We perform the microseconds to loops calculation using a number of multiplies and shift rights. Each shift right rounds down the resulting value, which can result in delays shorter than requested. Ensure that we always round up. Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Diffstat (limited to 'arch/arm/lib')
-rw-r--r--arch/arm/lib/delay.S4
1 files changed, 4 insertions, 0 deletions
diff --git a/arch/arm/lib/delay.S b/arch/arm/lib/delay.S
index 8d6a8762ab88..3c9a05c8d20b 100644
--- a/arch/arm/lib/delay.S
+++ b/arch/arm/lib/delay.S
@@ -25,11 +25,15 @@ ENTRY(__udelay)
ldr r2, .LC1
mul r0, r2, r0
ENTRY(__const_udelay) @ 0 <= r0 <= 0x7fffff06
+ mov r1, #-1
ldr r2, .LC0
ldr r2, [r2] @ max = 0x01ffffff
+ add r0, r0, r1, lsr #32-14
mov r0, r0, lsr #14 @ max = 0x0001ffff
+ add r2, r2, r1, lsr #32-10
mov r2, r2, lsr #10 @ max = 0x00007fff
mul r0, r2, r0 @ max = 2^32-1
+ add r0, r0, r1, lsr #32-6
movs r0, r0, lsr #6
moveq pc, lr