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>

1 files changed, 4 insertions, 0 deletions

diff --git a/arch/arm/lib/delay.S b/arch/arm/lib/delay.S
index 8d6a8762ab8..3c9a05c8d20 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