RFC, GIC based smp_cross_call cleanup suggestion

[Grant Likely]

On Sat, Apr 2, 2011 at 3:10 AM, Colin Cross <ccross at google.com> wrote:
> On Sat, Apr 2, 2011 at 1:51 AM, Russell King - ARM Linux
> <linux at arm.linux.org.uk> wrote:
>> On Fri, Apr 01, 2011 at 04:55:02PM -0600, Grant Likely wrote:
>>> On Fri, Apr 1, 2011 at 4:26 PM, John Linn <John.Linn at xilinx.com> wrote:
>>> > I’m getting ready to submit a patch to add SMP to Xilinx code. I notice that
>>> > smp_cross_call for all GIC based platforms is duplicated across each
>>> > platform in smp.h.
>>> >
>>> >
>>> >
>>> > I thought I’d try to jump in to help with some cleanup, although I realize
>>> > it’s minimal, I have to start somewhere.
>>> >
>>> >
>>> >
>>> > What about moving the smp_cross_call for GIC based designs into gic.h?
>>>
>>> Go for it.  It's an obvious cleanup.
>>
>> That assumes that all SMP implementations will always have a GIC.  It
>> looks to me like this is conditional on shmobile, and so I don't think
>> its that trivial - maybe Paul or Magnus can first indicate why this is.
>
> OMAP4 may also require a custom smp_cross_call implementation if CPU
> idle is going to be supported in SMP - in CPU off idle modes, a GIC
> SGI will not wake the CPU, and a write directly to the CPU's power
> management controller or an external interrupt source would be
> required.

What John proposes appears to be a pretty sane default though.  It
would make sense to move it to common code, and require explicit
action on the part of the subarch to compile it out for a different
behaviour.  Requiring each subarch to define it explicitly doesn't
seem optimal.

g.

-- 
Grant Likely, B.Sc., P.Eng.
Secret Lab Technologies Ltd.