[PATCH 1/2] tick: broadcast: Deny per-cpu clockevents from being broadcast sources

[Sören Brinkmann]

On Thu, Aug 22, 2013 at 10:06:40AM -0700, Stephen Boyd wrote:
> On most ARM systems the per-cpu clockevents are truly per-cpu in
> the sense that they can't be controlled on any other CPU besides
> the CPU that they interrupt. If one of these clockevents were to
> become a broadcast source we will run into a lot of trouble
> because the broadcast source is enabled on the first CPU to go
> into deep idle (if that CPU suffers from FEAT_C3_STOP) and that
> could be a different CPU than what the clockevent is interrupting
> (or even worse the CPU that the clockevent interrupts could be
> offline).
> 
> Theoretically it's possible to support per-cpu clockevents as the
> broadcast source but so far we haven't needed this and supporting
> it is rather complicated. Let's just deny the possibility for now
> until this becomes a reality (let's hope it never does!).
> 
> Reported-by: Sören Brinkmann <soren.brinkmann at xilinx.com>
> Signed-off-by: Stephen Boyd <sboyd at codeaurora.org>
Tested-by: Sören Brinkmann <soren.brinkmann at xilinx.com>

This fixes the issue I reported when enabling the global timer on Zynq.
The global timer is prevented from becoming the broadcast device and my
system boots.

	Thanks,
	Sören