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From: Guenter Roeck <linux@roeck-us.net>
To: Adam Thomson <Adam.Thomson.Opensource@diasemi.com>,
	Marco Felsch <m.felsch@pengutronix.de>
Cc: 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 05:38:01 -0800
Message-ID: <1feb2b8e-af46-ffa9-873a-fd9b624294b9@roeck-us.net> (raw)
In-Reply-To: <AM5PR1001MB099461A4E8253F74FC11D6E480430@AM5PR1001MB0994.EURPRD10.PROD.OUTLOOK.COM>

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 ?

Guenter


  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 [this message]
2019-12-02 14:44             ` Marco Felsch
2019-12-02 14:44             ` Adam Thomson
2019-12-02 15:06               ` Marco Felsch
2019-12-02 15:17                 ` Adam Thomson

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