linux-kernel - Re: [PATCH v5 1/5] powerpc/85xx: implement hardware timebase sync

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Message-ID: <20120607040701.GA15965@localhost.localdomain>
Date:	Thu, 7 Jun 2012 12:07:01 +0800
From:	Zhao Chenhui <chenhui.zhao@...escale.com>
To:	Scott Wood <scottwood@...escale.com>
CC:	<linuxppc-dev@...ts.ozlabs.org>, <linux-kernel@...r.kernel.org>,
	<galak@...nel.crashing.org>, <leoli@...escale.com>,
	Matthew McClintock <msm@...escale.com>
Subject: Re: [PATCH v5 1/5] powerpc/85xx: implement hardware timebase sync

On Wed, Jun 06, 2012 at 01:26:16PM -0500, Scott Wood wrote:
> On 06/06/2012 04:31 AM, Zhao Chenhui wrote:
> > On Tue, Jun 05, 2012 at 11:07:41AM -0500, Scott Wood wrote:
> >> On 06/05/2012 04:08 AM, Zhao Chenhui wrote:
> >>> On Fri, Jun 01, 2012 at 10:40:00AM -0500, Scott Wood wrote:
> >>>> I know you say this is for dual-core chips only, but it would be nice if
> >>>> you'd write this in a way that doesn't assume that (even if the
> >>>> corenet-specific timebase freezing comes later).
> >>>
> >>> At this point, I have not thought about how to implement the cornet-specific timebase freezing.
> >>
> >> I wasn't asking you to.  I was asking you to not have logic that breaks
> >> with more than 2 CPUs.
> > 
> > These routines only called in the dual-core case. 
> 
> Come on, you know we have chips with more than two cores.  Why design
> such a limitation into it, just because you're not personally interested
> in supporting anything but e500v2?
> 
> Is it so hard to make it work for an arbitrary number of cores?
> 
> >>> If do not set them, it may make KEXEC fail on other platforms.
> >>
> >> What platforms?
> > 
> > Such as P4080, P3041, etc.
> 
> So we need to wait for corenet timebase sync before we stop causing
> problems in virtualization, simulators, etc. if a kernel has kexec or
> cpu hotplug enabled (whether used or not)?
> 
> Can you at least make sure we're actually in a kexec/hotplug scenario at
> runtime?
> 
> Or just implement corenet timebase sync -- it's not that different.
> 
> -Scott

We also work on the corenet timebase sync. Our plan is first the dual-core case,
then the case of more than 2 cores. We will submit the corenet timebase sync patch soon.

-Chenhui

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