Re: RFC, GIC based smp_cross_call cleanup suggestion

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+ Thomas G,

On 4/2/2011 2:40 PM, Colin Cross wrote:
On Sat, Apr 2, 2011 at 1:51 AM, Russell King - ARM Linux
<linux@xxxxxxxxxxxxxxxx>  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@xxxxxxxxxx>  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.

This can be done without making smp_cross_call() platform
specific.
While working on broad-cast notifiers for ARM with Thomas G, this
point was discussed.

Where the TWD can't wakeup its own local CPU from C3 mode, how do we
provide a platform specific method to perform this wakeup ?

Thomas Quoted....
"It would not complicate the OMAP code that much. All it needs is
extending the clock event device callbacks by an broadcast_affinity()
function which would be called from the broadcast code when the
broadcast device is armed. The argument would be a cpumask which would
tell you which core(s) to wake up when the broadcast timer fires next.

So OMAP would fill in that hook and implement the wakeup redirector
setup, which I guess would be a couple of lines."

From above it's should be trivial once the broad-cast notifiers
are extended to have "broadcast_affinity()" supported

Regards
Santosh



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