Re: [PATCH v4 2/5] arm: add new asm macro update_sctlr

From: Will Deacon
Date: Wed Jan 22 2014 - 06:21:41 EST


On Sat, Jan 11, 2014 at 01:05:21PM +0000, Leif Lindholm wrote:
> A new macro for setting/clearing bits in the SCTLR.
>
> Signed-off-by: Leif Lindholm <leif.lindholm@xxxxxxxxxx>
> Suggested-by: Will Deacon <will.deacon@xxxxxxx>
> ---
> arch/arm/include/asm/assembler.h | 13 +++++++++++++
> 1 file changed, 13 insertions(+)
>
> diff --git a/arch/arm/include/asm/assembler.h b/arch/arm/include/asm/assembler.h
> index 5c22851..aba6458 100644
> --- a/arch/arm/include/asm/assembler.h
> +++ b/arch/arm/include/asm/assembler.h
> @@ -383,4 +383,17 @@ THUMB( orr \reg , \reg , #PSR_T_BIT )
> #endif
> .endm
>
> +#ifdef CONFIG_CPU_CP15
> +/* Macro for setting/clearing bits in sctlr */
> + .macro update_sctlr, set:req, clear:req, tmp:req, tmp2:req
> + mrc p15, 0, \tmp, c1, c0, 0
> + ldr \tmp2, =\set
> + orr \tmp, \tmp, \tmp2
> + ldr \tmp2, =\clear
> + mvn \tmp2, \tmp2
> + and \tmp, \tmp, \tmp2
> + mcr p15, 0, \tmp, c1, c0, 0

I think this would be cleaner if you force the caller to put set and clear
into registers beforehand, rather than have to do the literal load every
time. Also, I don't think set and clear should be required (and then you can
lose tmp2 as well).

Will
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