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

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Date:	Thu, 11 Jun 2015 13:44:58 +0800
From:	Fu Wei <fu.wei@...aro.org>
To:	Guenter Roeck <linux@...ck-us.net>
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

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

>
> Guenter
>



-- 
Best regards,

Fu Wei
Software Engineer
Red Hat Software (Beijing) Co.,Ltd.Shanghai Branch
Ph: +86 21 61221326(direct)
Ph: +86 186 2020 4684 (mobile)
Room 1512, Regus One Corporate Avenue,Level 15,
One Corporate Avenue,222 Hubin Road,Huangpu District,
Shanghai,China 200021
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