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From: Alexandre Belloni <alexandre.belloni@bootlin.com>
To: Ken Sloat <KSloat@aampglobal.com>
Cc: Guenter Roeck <linux@roeck-us.net>,
	"nicolas.ferre@microchip.com" <nicolas.ferre@microchip.com>,
	"ludovic.desroches@microchip.com"
	<ludovic.desroches@microchip.com>,
	"wim@linux-watchdog.org" <wim@linux-watchdog.org>,
	"linux-arm-kernel@lists.infradead.org" 
	<linux-arm-kernel@lists.infradead.org>,
	"linux-watchdog@vger.kernel.org" <linux-watchdog@vger.kernel.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v2 1/1] watchdog: atmel: atmel-sama5d4-wdt: Disable watchdog on system suspend
Date: Fri, 14 Jun 2019 22:33:27 +0200
Message-ID: <20190614203327.GE3369@piout.net> (raw)
In-Reply-To: <BL0PR07MB4115D5ECDEDCC028197637E5ADEE0@BL0PR07MB4115.namprd07.prod.outlook.com>

On 14/06/2019 18:43:22+0000, Ken Sloat wrote:
> Well I'm a little confused still because there are two separate comments
> in these statements. The first within resume implies that the init should
> be called because we might have lost register values for some reason
> unexplained.

The sama5d2 has a suspend mode where power to the core is completely
cut. Only a few IPs remain powered (in the backup power domain).
Unfortunately, the watchdog is not in that domain and may lose its
registers.

> Then within the init it says that the bootloader might have
> modified the registers so we should check them and then update it or
> otherwise disable it. I'm not trying to pick apart the logic or anything, 
> I'm just readily assuming it is good as it was already reviewed before. 
> 

The bootloaders may have started the watchdog (this makes sense if you
really care about reliability) and so we need to be careful to keep the
proper parameters.

> So without digging into that too much, if we don't know if any of the runtime
> situations above might have occurred, then isn't it best to leave my patch
> as is? Yes this has the side effect of resetting the timer count, but if 
> the init call is needed and we don't have any way to know if any
> of the situations occurred, then we have no choice right?
> 

Until we can differentiate between suspend modes, we have no other
choice.

-- 
Alexandre Belloni, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com

  reply index

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-06-14 12:53 Ken Sloat
2019-06-14 16:46 ` Guenter Roeck
2019-06-14 17:53   ` Ken Sloat
2019-06-14 18:08     ` Alexandre Belloni
2019-06-14 18:43       ` Ken Sloat
2019-06-14 20:33         ` Alexandre Belloni [this message]
2019-06-14 20:45           ` Ken Sloat
2019-06-15 14:22             ` Guenter Roeck
2019-06-20  8:33 ` Alexandre Belloni
2019-07-02 13:40 ` Guenter Roeck

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