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 [thread overview]
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
WARNING: multiple messages have this Message-ID (diff)
From: Alexandre Belloni <alexandre.belloni@bootlin.com>
To: Ken Sloat <KSloat@aampglobal.com>
Cc: "linux-watchdog@vger.kernel.org" <linux-watchdog@vger.kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"ludovic.desroches@microchip.com"
<ludovic.desroches@microchip.com>,
Guenter Roeck <linux@roeck-us.net>,
"wim@linux-watchdog.org" <wim@linux-watchdog.org>,
"linux-arm-kernel@lists.infradead.org"
<linux-arm-kernel@lists.infradead.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 [thread overview]
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
_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
next prev parent reply other threads:[~2019-06-14 20:33 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-06-14 12:53 [PATCH v2 1/1] watchdog: atmel: atmel-sama5d4-wdt: Disable watchdog on system suspend Ken Sloat
2019-06-14 12:53 ` Ken Sloat
2019-06-14 16:46 ` Guenter Roeck
2019-06-14 16:46 ` Guenter Roeck
2019-06-14 17:53 ` Ken Sloat
2019-06-14 17:53 ` Ken Sloat
2019-06-14 18:08 ` Alexandre Belloni
2019-06-14 18:08 ` Alexandre Belloni
2019-06-14 18:43 ` Ken Sloat
2019-06-14 18:43 ` Ken Sloat
2019-06-14 20:33 ` Alexandre Belloni [this message]
2019-06-14 20:33 ` Alexandre Belloni
2019-06-14 20:45 ` Ken Sloat
2019-06-14 20:45 ` Ken Sloat
2019-06-15 14:22 ` Guenter Roeck
2019-06-15 14:22 ` Guenter Roeck
2019-06-20 8:33 ` Alexandre Belloni
2019-06-20 8:33 ` Alexandre Belloni
2019-07-02 13:40 ` Guenter Roeck
2019-07-02 13:40 ` Guenter Roeck
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