linux-kernel - Re: [PATCH non-pretimeout 4/7] Watchdog: introduce ARM SBSA watchdog driver

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Date:	Wed, 10 Jun 2015 22:49:37 -0700
From:	Guenter Roeck <linux@...ck-us.net>
To:	Fu Wei <fu.wei@...aro.org>
CC:	Suravee Suthikulpanit <Suravee.Suthikulpanit@....com>,
	Linaro ACPI Mailman List <linaro-acpi@...ts.linaro.org>,
	linux-watchdog@...r.kernel.org, devicetree@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-doc@...r.kernel.org,
	Wei Fu <tekkamanninja@...il.com>,
	G Gregory <graeme.gregory@...aro.org>,
	Al Stone <al.stone@...aro.org>,
	Hanjun Guo <hanjun.guo@...aro.org>,
	Timur Tabi <timur@...eaurora.org>,
	Ashwin Chaugule <ashwin.chaugule@...aro.org>,
	Arnd Bergmann <arnd@...db.de>,
	Vipul Gandhi <vgandhi@...eaurora.org>,
	Wim Van Sebroeck <wim@...ana.be>,
	Jon Masters <jcm@...hat.com>, Leo Duran <leo.duran@....com>,
	Jon Corbet <corbet@....net>,
	Mark Rutland <mark.rutland@....com>,
	Catalin Marinas <catalin.marinas@....com>,
	Will Deacon <will.deacon@....com>, rjw@...ysocki.net
Subject: Re: [PATCH non-pretimeout 4/7] Watchdog: introduce ARM SBSA watchdog
 driver

On 06/10/2015 10:44 PM, Fu Wei wrote:
> Hi Guenter,
>
> On 11 June 2015 at 13:33, Guenter Roeck <linux@...ck-us.net> wrote:
>> On 06/10/2015 10:47 AM, fu.wei@...aro.org wrote:
>>>
>>> From: Fu Wei <fu.wei@...aro.org>
>>>
>>> This driver bases on linux kernel watchdog framework.
>>> It supports getting timeout from parameter and FDT
>>> at the driver init stage.
>>> The first timeout period expires, the interrupt routine
>>> got another timeout period to run panic for saving
>>> system context.
>>>
>>> Signed-off-by: Fu Wei <fu.wei@...aro.org>
>>> ---
>>>    drivers/watchdog/Kconfig     |  11 ++
>>>    drivers/watchdog/Makefile    |   1 +
>>>    drivers/watchdog/sbsa_gwdt.c | 383
>>> +++++++++++++++++++++++++++++++++++++++++++
>>>    3 files changed, 395 insertions(+)
>>>    create mode 100644 drivers/watchdog/sbsa_gwdt.c
>>>
>>> diff --git a/drivers/watchdog/Kconfig b/drivers/watchdog/Kconfig
>>> index e5e7c55..554f18a 100644
>>> --- a/drivers/watchdog/Kconfig
>>> +++ b/drivers/watchdog/Kconfig
>>> @@ -152,6 +152,17 @@ config ARM_SP805_WATCHDOG
>>>            ARM Primecell SP805 Watchdog timer. This will reboot your system
>>> when
>>>            the timeout is reached.
>>>
>>> +config ARM_SBSA_WATCHDOG
>>> +       tristate "ARM SBSA Generic Watchdog"
>>> +       depends on ARM64
>>> +       depends on ARM_ARCH_TIMER
>>> +       select WATCHDOG_CORE
>>> +       help
>>> +         ARM SBSA Generic Watchdog. This watchdog has two Watchdog
>>> timeouts.
>>> +         The first timeout will trigger a panic; the second timeout will
>>> +         trigger a system reset.
>>> +         More details: ARM DEN0029B - Server Base System Architecture
>>> (SBSA)
>>> +
>>>    config AT91RM9200_WATCHDOG
>>>          tristate "AT91RM9200 watchdog"
>>>          depends on SOC_AT91RM9200 && MFD_SYSCON
>>> diff --git a/drivers/watchdog/Makefile b/drivers/watchdog/Makefile
>>> index 5c19294..471f1b7c 100644
>>> --- a/drivers/watchdog/Makefile
>>> +++ b/drivers/watchdog/Makefile
>>> @@ -30,6 +30,7 @@ obj-$(CONFIG_USBPCWATCHDOG) += pcwd_usb.o
>>>
>>>    # ARM Architecture
>>>    obj-$(CONFIG_ARM_SP805_WATCHDOG) += sp805_wdt.o
>>> +obj-$(CONFIG_ARM_SBSA_WATCHDOG) += sbsa_gwdt.o
>>>    obj-$(CONFIG_AT91RM9200_WATCHDOG) += at91rm9200_wdt.o
>>>    obj-$(CONFIG_AT91SAM9X_WATCHDOG) += at91sam9_wdt.o
>>>    obj-$(CONFIG_CADENCE_WATCHDOG) += cadence_wdt.o
>>> diff --git a/drivers/watchdog/sbsa_gwdt.c b/drivers/watchdog/sbsa_gwdt.c
>>> new file mode 100644
>>> index 0000000..1ddc10f
>>> --- /dev/null
>>> +++ b/drivers/watchdog/sbsa_gwdt.c
>>> @@ -0,0 +1,383 @@
>>> +/*
>>> + * SBSA(Server Base System Architecture) Generic Watchdog driver
>>> + *
>>> + * Copyright (c) 2015, Linaro Ltd.
>>> + * Author: Fu Wei <fu.wei@...aro.org>
>>> + *         Suravee Suthikulpanit <Suravee.Suthikulpanit@....com>
>>> + *
>>> + * This program is free software; you can redistribute it and/or modify
>>> + * it under the terms of the GNU General Public License 2 as published
>>> + * by the Free Software Foundation.
>>> + *
>>> + * This program is distributed in the hope that it will be useful,
>>> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
>>> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
>>> + * GNU General Public License for more details.
>>> + *
>>> + * Note: This SBSA Generic watchdog has two stage timeouts,
>>> + *       When the first timeout occurs, WS0(SPI or LPI) is triggered,
>>> + *       the second timeout period(as long as the first timeout period)
>>> starts.
>>> + *       In WS0 interrupt routine, panic() will be called for collecting
>>> + *       crashdown info.
>>> + *       If system can not recover from WS0 interrupt routine, then
>>> second
>>> + *       timeout occurs, WS1(reset or higher level interrupt) is
>>> triggered.
>>> + *       The two timeout period can be set by WOR(32bit).
>>> + *       WOR gives a maximum watch period of around 10s at the maximum
>>> + *       system counter frequency.
>>> + *       The System Counter shall run at maximum of 400MHz.
>>> + *
>>> + *       But If we need a larger timeout period, this driver will
>>> programme WCV
>>> + *       directly. That can support more than 10s timeout at the maximum
>>> + *       system counter frequency.
>>> + *       More details: ARM DEN0029B - Server Base System Architecture
>>> (SBSA)
>>> + *
>>> + * SBSA GWDT:    |---WOR(or WCV)---WS0---WOR(or WCV)---WS1
>>> + *               |-----timeout-----WS0-----timeout-----WS1
>>
>>
>> If we use WCV at all, I would like to see something like
>>
>>   * SBSA GWDT:    |---WOR(or WCV)---WS0--------WOR------WS1
>>   *               |-----timeout-----WS0-----------------WS1
>>   *                                 panic               hw reset
>>
>> where WOR would be used up to its maximum, to be replaced by WCV
>> (but kept at maximum) if the selected timeout is larger than the
>> maximum timeout selectable with WOR. Would this be possible ?
>
> for this part |-----timeout-----WS0,  I am doing this way in
> non-pretimeout version.
>
> but for WS0-----------------WS1, do you mean WOR would always be used
> up to its maximum???

yes

> I don't see any variable attached on it. So I would like to confirm
> what is this value
>

min(timeout, max_wor_timeout)

Guenter

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