[PATCH] ARM: smp: Allow real broadcast device selection instead of always dummy

Thomas Gleixner tglx at linutronix.de
Wed Mar 13 10:19:07 EDT 2013

On Wed, 13 Mar 2013, Santosh Shilimkar wrote:
> On Wednesday 13 March 2013 02:36 PM, Santosh Shilimkar wrote:
> > With recent arm broadcast time clean-up from Mark Rutland, the dummy
> > broadcast device is always registered with timer subsystem. And since
> > the rating of the dummy clock event is very high, it is preferred
> > over a real broad-cast clock event.
> > 
> > This is a change in behavior from past and not an intended
> > one. So reduce the rating of the dummy clockevent so that
> > real broadcast device is selected when available.
> > 
> > Without this all the C states with C3STOP won't work since
> > the broad cast notifier will take an abort.
> > 
> > Cc: Mark Rutland <mark.rutland at arm.com>
> > Cc: Russell King <linux at arm.linux.org.uk>
> > 
> > Signed-off-by: Santosh Shilimkar <santosh.shilimkar at ti.com>
> > ---
> > Its a regression so hopefully can get into the 3.9-rcx. Noticed
> > this one on A15 platform. A9 platform the issue may not be seen
> > since the local timer check avoids dummy timer registration.
> > 
> Some one pointed me to a fix made by Mark which was discussed
> under '[BUG] ARM Architected timers appear broken in 3.9-rc1' subject.
> That patch seems to be more of work around since the root of the
> problem is incorrect dummy timer rating. Either way, both patches
> fix the issue.

Well, using a dummy timer as the broadcast event device is a bug, no
matter what the rating is. The fix is in Linus tree already.

Though making the rating of the dummy lower is definitely a good
thing, so a real hardware device which is detected later can replace
the dummy device. So yes, the rating should be low for the dummy



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