[PATCH 07/13] arm64: Add new routine local_disable

[Mark Rutland]

Hi Geoff,

On Tue, Sep 09, 2014 at 11:49:04PM +0100, Geoff Levand wrote:
> Add the new arm64 routine local_disable() to allow the masking of several DAIF
> flags in one operation.  Currently, we only have routines to mask individual
> flags, and to mask several flags multiple calls to daifset are required.
>
> Signed-off-by: Geoff Levand <geoff at infradead.org>
> ---
>  arch/arm64/include/asm/irqflags.h | 13 +++++++++++++
>  1 file changed, 13 insertions(+)
> 
> diff --git a/arch/arm64/include/asm/irqflags.h b/arch/arm64/include/asm/irqflags.h
> index 11cc941..28521d4 100644
> --- a/arch/arm64/include/asm/irqflags.h
> +++ b/arch/arm64/include/asm/irqflags.h
> @@ -113,5 +113,18 @@ static inline int arch_irqs_disabled_flags(unsigned long flags)
>  #define local_dbg_enable()	asm("msr	daifclr, #8" : : : "memory")
>  #define local_dbg_disable()	asm("msr	daifset, #8" : : : "memory")
>  
> +enum daif_flag {

Is there any reason for this to be an enum rather than a set of
#defines?

It would be nice to be able to use these in asm.

> +	DAIF_FIQ   = (1UL << 6),
> +	DAIF_IRQ   = (1UL << 7),
> +	DAIF_ASYNC = (1UL << 8),
> +	DAIF_DBG   = (1UL << 9),
> +	DAIF_ALL   = (0xffUL << 6),

Not 0xf?

It would be nicer to OR the other flags.

> +};
> +
> +static inline void local_disable(unsigned long daif_flags)
> +{
> +	arch_local_irq_restore(daif_flags | arch_local_save_flags());

If we knew the value was a constant (which we could check with
__builting_constant_p) we could use daifset here, rather than having a
RMW sequence.

With that, the other local_*_{enable,disable} calls could be rewritten
in terms of this, without affecting the generated code. That would
require some shifting to account for the difference between pstate and
daif{clr,set} layout, but for constants that shouldn't be a problem.

Thanks,
Mark.