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From: Marco Felsch <m.felsch@pengutronix.de>
To: Adam Thomson <Adam.Thomson.Opensource@diasemi.com>
Cc: Guenter Roeck <linux@roeck-us.net>,
	"wim@linux-watchdog.org" <wim@linux-watchdog.org>,
	Support Opensource <Support.Opensource@diasemi.com>,
	"kernel@pengutronix.de" <kernel@pengutronix.de>,
	"linux-watchdog@vger.kernel.org" <linux-watchdog@vger.kernel.org>
Subject: Re: [PATCH] watchdog: da9062: add power management ops
Date: Mon, 2 Dec 2019 16:06:01 +0100
Message-ID: <20191202150601.r3qb3b3kaezlihee@pengutronix.de> (raw)
In-Reply-To: <AM5PR1001MB0994B8FDCC3C1B991433344780430@AM5PR1001MB0994.EURPRD10.PROD.OUTLOOK.COM>

On 19-12-02 14:44, Adam Thomson wrote:
> On 02 December 2019 13:38, Adam Thomson wrote:
> 
> > On 12/2/19 5:27 AM, Adam Thomson wrote:
> > > Hi Marco,
> > >
> > >>> Hmmm. Wouldn't that then be a board specific fix rather than this change?
> > >>> Am concerned relying on software to reenable the watchdog on resume
> > could
> > >> allow
> > >>> for a hang scenario potentially if that code never gets to execute. Other
> > >>> systems shouldn't need this fix, assuming they don't have issues at the HW
> > >>> level, so this this seems like it could be making those systems less robust. If
> > >>> we are to do this at the driver level, maybe this should be an option through
> > DT
> > >>> to help faulty systems, but I'm thinking this shouldn't be default behaviour.
> > >>
> > >> I don't think that we should rely on the OTP values. Those values are
> > >> set by Dialog, the SoM manufacturers or by the customer itself and the
> > >> time shows that this is error prone too. At least if the customer or the
> > >> SoM manufacturer don't ask the Dialog Support..
> > >>
> > >> You're right with the (re-)enabling but there are other drivers using
> > >> such an approach.. IMHO it is safer to go this way rather than trust
> > >> the OTP and the PCB layout. I would rather add a dt-compatible to tell
> > >> the driver to do nothing during suspend/resume e.g.:
> > >>
> > >>      - dlg,use-hw-pm
> > >>
> > >> or something. Because the user needs to validate the PCB and the OTP
> > >> values.
> > >
> > > The thing is the DT FW is supposed to be fairly static so I would rather not
> > > enforce this change on users if they adopt a kernel version with this update in.
> > > I also still think it's safer if the HW does this for us. I would have hoped for
> > > most designs this would be caught in early bring up where it can be rectified
> > > with minimal impact, although I'm guessing that's not the case in your scenario.
> > >
> > 
> > dla,use-sw-pm ?
> > dla,hw-pm-broken ?
> 
> Yes, I'd probably opt for 'dlg,use-sw-pm' or maybe 'dlg,manual-pm' to cover it.

Okay, so we are all agree with the dlg,use-sw-pm?

Regards,
  Marco

> 
> > 
> > Guenter

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  reply index

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-11-28 17:19 Marco Felsch
2019-11-28 17:41 ` Guenter Roeck
2019-12-02 10:04 ` Adam Thomson
2019-12-02 10:56   ` Marco Felsch
2019-12-02 11:11     ` Adam Thomson
2019-12-02 13:03       ` Marco Felsch
2019-12-02 13:27         ` Adam Thomson
2019-12-02 13:38           ` Guenter Roeck
2019-12-02 14:44             ` Marco Felsch
2019-12-02 14:44             ` Adam Thomson
2019-12-02 15:06               ` Marco Felsch [this message]
2019-12-02 15:17                 ` Adam Thomson

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