Re: [PATCH v1 5/5] coresight: etm4x: save/restore state across CPU low power states

From: Mathieu Poirier <mathieu.poirier@linaro.org>
To: Andrew Murray <andrew.murray@arm.com>
Cc: Al Grant <Al.Grant@arm.com>,
	Suzuki K Poulose <suzuki.poulose@arm.com>,
	Alexander Shishkin <alexander.shishkin@linux.intel.com>,
	Sudeep Holla <Sudeep.Holla@arm.com>,
	linux-arm-kernel <linux-arm-kernel@lists.infradead.org>,
	Mike Leach <mike.leach@linaro.org>
Subject: Re: [PATCH v1 5/5] coresight: etm4x: save/restore state across CPU low power states
Date: Fri, 21 Jun 2019 09:30:39 -0600	[thread overview]
Message-ID: <CANLsYkygS1QzRr_ef783ZCTLn0QL1CV=EGoMhDtK=Nyn9BUy6g@mail.gmail.com> (raw)
In-Reply-To: <20190621092948.GJ20984@e119886-lin.cambridge.arm.com>

On Fri, 21 Jun 2019 at 03:29, Andrew Murray <andrew.murray@arm.com> wrote:
>
> On Thu, Jun 20, 2019 at 11:10:26AM -0600, Mathieu Poirier wrote:
> > On Thu, 20 Jun 2019 at 11:00, Suzuki K Poulose <suzuki.poulose@arm.com> wrote:
> > >
> > >
> > >
> > > On 20/06/2019 17:54, Andrew Murray wrote:
> > > > On Thu, Jun 20, 2019 at 10:47:38AM -0600, Mathieu Poirier wrote:
> > > >> On Thu, 20 Jun 2019 at 10:34, Sudeep Holla <sudeep.holla@arm.com> wrote:
> > > >>>
> > > >>> On Thu, Jun 20, 2019 at 10:14:04AM -0600, Mathieu Poirier wrote:
> > > >>>> On Thu, 20 Jun 2019 at 09:41, Sudeep Holla <sudeep.holla@arm.com> wrote:
> > >
> > > ...
> > >
> > > >> Then all we have to do is make the ACPI/DT property that indicate the
> > > >> method used to deal with tracer idling mandatory.  That way people are
> > > >> conscious of the choice they are making.  To be backward compatible
> > > >> with current systems we default to the TRCPDCR.PU method but print a
> > > >> warning message, just like we do for obsolete DT bindings.
> > > >
> > > > I'll respin the series based on this approach. I'll also flip the
> > > > 'disable_pm_save' module option to 'enable_pm_save' - thus allowing any
> > > > one to use software save/restore if they wish.
> > >
> > > If you are going to add a firmware property, please get a consensus on the
> > > name here, before respinning to avoid another churn :-). How about one of :
> > >
> > > "arm,coresight-etm-looses-state"
> > > "arm,coresight-etm-needs-save-restore"
> >
> > "arm,coresight-needs-save-restore"
> >
> > That way we can also use it for CTI.
>
> I have no objections with "arm,coresight-needs-save-restore", however in
> trying to come up with a name that describes the hardware rather than
> something software needs to do, I came up with:
>
>  "arm,coresight-broken-pu"
>  "arm,coresight-no-pu"
>  "arm,coresight-pu-ignored"
>
> Are any of these prefered?

None of the above because 1) the case we are dealing with as been
inaccurately labeled as "broken" and 2) anything referring to "pu" is
exclusively related to ETMs.

>
> Thanks,
>
> Andrew Murray
>
> >
> > >
> > > or something better long the line.
> > >
> > > Cheers
> > > Suzuki
> > >
> > > _______________________________________________
> > > linux-arm-kernel mailing list
> > > linux-arm-kernel@lists.infradead.org
> > > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

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