[PATCH] ARM: v6: avoid read_cpuid_ext() on ARM1136r0 in cache_ops_need_broadcast()

[Paul Walmsley]

On Sun, 28 Jul 2013, Russell King - ARM Linux wrote:

> We don't want to make the asm() itself volatile, because that means the 
> asm() statement can't be optimised away.
> 
> Adding a memory clobber to that asm seems to place it more appropriately,
> but again, that's not particularly desirable.
> 
> Another solution would be to make both tlb_ops_need_broadcast and
> cache_ops_need_broadcast both be a flag test, but that introduces a
> memory load in all those paths no matter if we're running on SMP_ON_UP
> or not.

I considered adding a HWCAP_* bit under the theory that elf_hwcap may 
already be cache-resident.  But thought that the loss of the flag space 
and possible memory access vs. the additional mrc wasn't worth it.

Anyway, if either of you have a preference between these three, I'd be 
happy to update the patch.  Or feel free to take it over from here if 
either of you prefer.


- Paul