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

[Guenter Roeck]

On 06/10/2015 10:44 PM, Fu Wei wrote:
> Hi Guenter,
>
> On 11 June 2015 at 13:33, Guenter Roeck <linux@xxxxxxxxxxxx> wrote:
> > On 06/10/2015 10:47 AM, fu.wei@xxxxxxxxxx wrote:
> > > From: Fu Wei <fu.wei@xxxxxxxxxx>
> > >
> > > 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@xxxxxxxxxx>
> > > ---
> > >    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@xxxxxxxxxx>
> > > + *         Suravee Suthikulpanit <Suravee.Suthikulpanit@xxxxxxx>
> > > + *
> > > + * 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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