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ARM: udelay: prevent math rounding resulting in short udelays

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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>
This commit is contained in:
Russell King 2011-01-10 23:55:59 +00:00
parent 9e9bc97367
commit 56949d414a
1 changed files with 4 additions and 0 deletions
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4
arch/arm/lib/delay.S
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@ -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