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>
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@ -25,11 +25,15 @@ ENTRY(__udelay)
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ldr r2, .LC1
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ldr r2, .LC1
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mul r0, r2, r0
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mul r0, r2, r0
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ENTRY(__const_udelay) @ 0 <= r0 <= 0x7fffff06
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ENTRY(__const_udelay) @ 0 <= r0 <= 0x7fffff06
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mov r1, #-1
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ldr r2, .LC0
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ldr r2, .LC0
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ldr r2, [r2] @ max = 0x01ffffff
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ldr r2, [r2] @ max = 0x01ffffff
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add r0, r0, r1, lsr #32-14
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mov r0, r0, lsr #14 @ max = 0x0001ffff
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mov r0, r0, lsr #14 @ max = 0x0001ffff
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add r2, r2, r1, lsr #32-10
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mov r2, r2, lsr #10 @ max = 0x00007fff
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mov r2, r2, lsr #10 @ max = 0x00007fff
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mul r0, r2, r0 @ max = 2^32-1
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mul r0, r2, r0 @ max = 2^32-1
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add r0, r0, r1, lsr #32-6
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movs r0, r0, lsr #6
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movs r0, r0, lsr #6
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moveq pc, lr
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moveq pc, lr
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