linux-kernel - Re: [PATCH] thermal: core: Add a back up thermal shutdown mechanism

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Message-ID: <20170412040542.GA11305@localhost.localdomain>
Date:   Tue, 11 Apr 2017 21:05:46 -0700
From:   Eduardo Valentin <edubezval@...il.com>
To:     Keerthy <j-keerthy@...com>
Cc:     Zhang Rui <rui.zhang@...el.com>, linux-pm@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-omap@...r.kernel.org,
        nm@...com, t-kristo@...com
Subject: Re: [PATCH] thermal: core: Add a back up thermal shutdown mechanism

Keerthy,

On Wed, Apr 12, 2017 at 09:09:36AM +0530, Keerthy wrote:
> 
> 
> On Wednesday 12 April 2017 08:50 AM, Zhang Rui wrote:
> > On Wed, 2017-04-12 at 08:19 +0530, Keerthy wrote:
> >>
> >> On Tuesday 11 April 2017 10:59 PM, Eduardo Valentin wrote:
> >>>
> >>> Hey,
> >>>
> >>> On Fri, Mar 31, 2017 at 12:00:20PM +0530, Keerthy wrote:
> >>>>
> >>>> off).

<cut>

> >>> OK... This seams to me, still a corner case supposed to be fixed at
> >>> orderly_power_off, not at thermal. But..
> >>>

^^^ Then again, this must be fixed not at thermal core. And re-reading
the history of this thread, this seams to be really something broken at
OMAP/DRA7, as mentioned in previous messages. That is probably why you
are pushing for pm_power_off(), which seams to be the one that works for
you, pulling the plug correctly (DRA7).

> >>>>
> >>>>
> >>>> However, there is no clean way of detecting such failure of
> >>>> userspace
> >>>> powering off the system. In such scenarios, it is necessary for a
> >>>> backup
> >>>> workqueue to be able to force a shutdown of the system when
> >>>> orderly
> >>>> shutdown is not successful after a configurable time period.
> >>>>
> >>> Given that system running hot is a thermal issue, I guess we care
> >>> more
> >>> on this matter then..
> >> Yes!
> >>
> > I just read this thread again https://patchwork.kernel.org/patch/802458
> > 1/ to recall the previous discussion.
> > 
> > https://patchwork.kernel.org/patch/8149891/
> > https://patchwork.kernel.org/patch/8149861/
> > should be the solution made based on Ingo' suggestion, right?
> > 
> > And to me, this sounds like the right direction to go, thermal does not
> > need a back up shutdown solution, it just needs a kernel function call
> > which guarantees the system can be shutdown/reboot immediately.
> > 
> > is there any reason that patch 1/2 is not accepted?
> 
> Zhang,
> 
> http://www.serverphorums.com/read.php?12,1400964
> 
> I got a NAK from Alan and was given this direction on a thermal_poweroff
> which is more or less what is done in this patch.
> 

Actually, Alan's suggestion is more for you to define a
thermal_poweroff() that can be defined per architecture.

Also, please, keep track of your patch versions and also do copy
everybody who has stated their opinion on previous discussions. These
patches must have Ingo, Alan, and RMK copied too. In this way we avoid
loosing track of what has been suggested and we also converge faster to
something everybody (or most of us) agree. Next version, please, fix
that.

To me, thermal core needs a function that simply powers off the system.
No timeouts, delayed works, backups, etc. Simple and straight.

The idea of having a per architecture implementation, as per Alan's
suggestion, makes sense to me too. Having something different from
pm_power_off(), specific to thermal, might also give the opportunity to
save the power off reason.

BR,

Eduardo Valentin

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