RE: [PATCH v3 2/4] watchdog: da9062: reset board on watchdog timeout

From: Christoph Niedermaier <cniedermaier@dh-electronics.com>
To: Andrej Picej <andrej.picej@norik.com>,
	"support.opensource@diasemi.com" <support.opensource@diasemi.com>,
	"linux@roeck-us.net" <linux@roeck-us.net>,
	"linux-watchdog@vger.kernel.org" <linux-watchdog@vger.kernel.org>
Cc: "wim@linux-watchdog.org" <wim@linux-watchdog.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"robh+dt@kernel.org" <robh+dt@kernel.org>,
	"devicetree@vger.kernel.org" <devicetree@vger.kernel.org>,
	"shawnguo@kernel.org" <shawnguo@kernel.org>,
	"s.hauer@pengutronix.de" <s.hauer@pengutronix.de>,
	"kernel@pengutronix.de" <kernel@pengutronix.de>,
	"festevam@gmail.com" <festevam@gmail.com>,
	"linux-imx@nxp.com" <linux-imx@nxp.com>,
	"linux-arm-kernel@lists.infradead.org"
	<linux-arm-kernel@lists.infradead.org>
Subject: RE: [PATCH v3 2/4] watchdog: da9062: reset board on watchdog timeout
Date: Thu, 2 Dec 2021 15:37:08 +0000	[thread overview]
Message-ID: <ae0838b3408746e188635f57ac942d5f@dh-electronics.com> (raw)
In-Reply-To: <9298e77a-d74e-f51a-187f-830da184e67d@norik.com>

From: Andrej Picej [mailto:andrej.picej@norik.com]
Sent: Thursday, December 2, 2021 8:43 AM

[...]
>> I have a question how to correctly restart the system after
>> watchdog timeout.
>> If I understand it correct after watchdog timeout the system
>> restarts only if WATCHDOG_SD (Bit 3) in register CONFIG_I is
>> set.
>> What is the difference if WATCHDOG_SD isn't set, but WAKE_UP
>> (Bit 2) in register CONTROL_F is set? From outside on my
>> system I observe the same behavior. After watchdog timeout
>> my system restarts. So where are the differences?
>> It would be nice if you could answer this question, as you
>> certainly know this chip very well.
> 
> To be honest I don't really know the chip that well, I'm just trying to
> add this feature and hopefully help others if they run into the same
> problem. I think @Adam will be more helpful here.
> 
> But from quick look at da9062 datasheet, mainly chapter "8.8 Power
> Modes" I see next main differences:
> - setting WATCHDOG_SD enables SHUTDOWN sequence when the watchdog
> timeout is triggered. This puts the chip (da9062) in RESET mode.
> Taken from DA9062 datasheet:
> > In RESET mode, the internal supplies, and LDO1 (if configured as an
> always-on supply) are enabled.
> > All other DA9062 supplies are disabled.
> > DA9062 is in RESET mode whenever a complete application shutdown is
> required
> > The DA9062’s register configuration will be re-loaded from OTP when
> leaving the RESET mode
> 
> - if you set the WAKE_UP bit than the chip enters POWERDOWN mode on
> watchdog timeout. I understand the POWERDOWN mode as a not that "deep"
> mode as a RESET mode Device will go from RESET mode to POWERDOWN mode in
> the sequence of powering-up.
> 
> The above explanation is just my understanding after quick look, @Adam
> please correct me if I'm talking nonsense.
> 
> Please have a look at the DA9062 datasheet for more information. Sorry,
> that I can't be more helpful here.

Hi Andrej,

Thanks a lot for your explanation. 
I think I would like to test your implementation, because this seems
to be the better way to restart the system to a reliable state.
I have a DA9061 which supplies an i.MX6ULL.
Would you be so kind to adapt your patch 1/4 for the DA9061?
For details I will also answer on your patch 1/4.

Thanks and regards
Christoph
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