Re: [PATCH] watchdog: da9062: add power management ops

From: Marco Felsch <m.felsch@pengutronix.de>
To: Guenter Roeck <linux@roeck-us.net>
Cc: Adam Thomson <Adam.Thomson.Opensource@diasemi.com>,
	Support Opensource <Support.Opensource@diasemi.com>,
	"wim@linux-watchdog.org" <wim@linux-watchdog.org>,
	"linux-watchdog@vger.kernel.org" <linux-watchdog@vger.kernel.org>,
	"kernel@pengutronix.de" <kernel@pengutronix.de>
Subject: Re: [PATCH] watchdog: da9062: add power management ops
Date: Mon, 2 Dec 2019 15:44:10 +0100	[thread overview]
Message-ID: <20191202144410.k4jqnysyxgrwqmu2@pengutronix.de> (raw)
In-Reply-To: <1feb2b8e-af46-ffa9-873a-fd9b624294b9@roeck-us.net>

On 19-12-02 05:38, Guenter Roeck 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.

Currently there is only the phytec-phycore upstream DT using the
da9061/2 PMIC... Anyway I got your concerns.

> dla,use-sw-pm ?
> dla,hw-pm-broken ?

Yes one of these. Which do you prefer Adam?

Regards,
  Marco 

> 
> Guenter
> 
> 

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