[PATCH v2] ARM: Define wfi() macro for v6 processors

[Dave Martin]

On Tue, Feb 8, 2011 at 3:42 PM, Arnd Bergmann <arnd at arndb.de> wrote:
> On Tuesday 08 February 2011, Dave Martin wrote:
>> Why not have macros for these cases?  (Which kinda brings the
>> discussion full-circle...)
>>
>> My immediate concern is that too often, the Thumb-2 case will be
>> handled incorrectly or not at all ... and the kernel will silently
>> build without flagging any error.  Macros would allow the fragile
>> definitions to go in one place.
>
> A macro to handle the thumb2 case and weird toolchains sounds good,
> but if we want to build code for multiple CPUs, we need multiple
> macros, not one macro that works on a specific CPU.
>
> We could put all those macros unconditionally into a arch
> specific header, e.g.
>
> arch/arm/include/asm/system-v7.h:
> #define wfi() __asm__ __volatile__ ("wfi" : : : "memory")
>
>
> arch/arm/include/asm/system-v6k.h:
> #define wfi() __asm__ __volatile__ ("mcr p15, 0, %0, c7, c0, 4" \
>                : : "r" (0) : "memory")
>
> And then have each C file using them be CPU specific and include
> only one (you get an gcc warning if you try to include both).
> This should work fine, but it's different again from how we handle
> other things like spinlocks or cache management across multiple
> CPUs.

Such a solution could work...

I have a (possibly silly) question ... are the definitions in
arm/system.h intended to be fully generic, or not?  Some features
suggest an attempt at genericness, but not everything there is
generic.  Maybe I have misconstrued the purpose of this header.

Cheers
---Dave