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

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Date:	Wed, 10 Jun 2015 22:33:33 -0700
From:	Guenter Roeck <linux@...ck-us.net>
To:	fu.wei@...aro.org, Suravee.Suthikulpanit@....com,
	linaro-acpi@...ts.linaro.org, linux-watchdog@...r.kernel.org,
	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-doc@...r.kernel.org
CC:	tekkamanninja@...il.com, graeme.gregory@...aro.org,
	al.stone@...aro.org, hanjun.guo@...aro.org, timur@...eaurora.org,
	ashwin.chaugule@...aro.org, arnd@...db.de, vgandhi@...eaurora.org,
	wim@...ana.be, jcm@...hat.com, leo.duran@....com, corbet@....net,
	mark.rutland@....com, catalin.marinas@....com, will.deacon@....com,
	rjw@...ysocki.net
Subject: Re: [PATCH non-pretimeout 4/7] Watchdog: introduce ARM SBSA watchdog
 driver

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 ?

Guenter

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