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>
diff --git a/arch/arm/lib/delay.S b/arch/arm/lib/delay.S
index 8d6a876..3c9a05c 100644
--- a/arch/arm/lib/delay.S
+++ b/arch/arm/lib/delay.S
@@ -25,11 +25,15 @@
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