Subject: [PATCH v10 5/5] Watchdog: ARM SBSA Generic Watchdog half timeout panic support

From: [email-masked] (Guenter Roeck)
Date: Thu, 4 Feb 2016 08:41:55 -0800

On 02/04/2016 08:32 AM, Mathieu Poirier wrote:
> On 3 February 2016 at 10:18,  <[email-masked]> wrote:
>> From: Fu Wei <[email-masked]>
>>
>> This patch registers the WS0 interrupt routine to trigger panic,
>> when the watchdog reachs the first stage (the half timeout).
>> This function can help administrator to backup the system context
>> info by panic console output or kdump (if supported), once system
>> goes wrong (doesn't feed the watchdog in the half timeout).
>>
>> User also can skip panic by setting panic_enabled (module parameter) as 0
>>
>> Signed-off-by: Fu Wei <[email-masked]>
>> ---
>>   Documentation/watchdog/watchdog-parameters.txt |  1 +
>>   drivers/watchdog/Kconfig                       | 10 +++++
>>   drivers/watchdog/sbsa_gwdt.c                   | 54 +++++++++++++++++++++++---
>>   3 files changed, 60 insertions(+), 5 deletions(-)
>>
>> diff --git a/Documentation/watchdog/watchdog-parameters.txt b/Documentation/watchdog/watchdog-parameters.txt
>> index 300eb4d..31641e2 100644
>> --- a/Documentation/watchdog/watchdog-parameters.txt
>> +++ b/Documentation/watchdog/watchdog-parameters.txt
>> @@ -286,6 +286,7 @@ nowayout: Watchdog cannot be stopped once started
>>   -------------------------------------------------
>>   sbsa_gwdt:
>>   timeout: Watchdog timeout in seconds. (default 20s)
>> +panic_enabled: Enable panic at half timeout. (default=true)
>>   nowayout: Watchdog cannot be stopped once started
>>          (default=kernel config parameter)
>>   -------------------------------------------------
>> diff --git a/drivers/watchdog/Kconfig b/drivers/watchdog/Kconfig
>> index 4ab1b05..42adfdf 100644
>> --- a/drivers/watchdog/Kconfig
>> +++ b/drivers/watchdog/Kconfig
>> @@ -218,6 +218,16 @@ config ARM_SBSA_WATCHDOG
>>            To compile this driver as module, choose M here: The module
>>            will be called sbsa_gwdt.
>>
>> +config ARM_SBSA_WATCHDOG_PANIC
>> +       bool "ARM SBSA Generic Watchdog triggers panic at the half timeout"
>> +       depends on ARM_SBSA_WATCHDOG
>> +       help
>> +         ARM SBSA Generic Watchdog will trigger panic in the first signal
>> +         (WS0) interrupt routine when the half timeout is reached.
>> +         This function can help administrator to backup the system context
>> +         info by panic console output or kdump (if supported).
>> +         But user can skip panic by setting moduleparam panic_enabled as 0.
>> +
>>   config ASM9260_WATCHDOG
>>          tristate "Alphascale ASM9260 watchdog"
>>          depends on MACH_ASM9260
>> diff --git a/drivers/watchdog/sbsa_gwdt.c b/drivers/watchdog/sbsa_gwdt.c
>> index 5a2dba3..d18cf37 100644
>> --- a/drivers/watchdog/sbsa_gwdt.c
>> +++ b/drivers/watchdog/sbsa_gwdt.c
>> @@ -16,18 +16,22 @@
>>    * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
>>    * GNU General Public License for more details.
>>    *
>> - * This SBSA Generic watchdog driver is a single stage timeout version.
>> + * This SBSA Generic watchdog driver is a two stages version.
>>    * Since this watchdog timer has two stages, and each stage is determined
>>    * by WOR. So the timeout is (WOR * 2).
>> - * When first timeout is reached, WS0 is triggered, the interrupt
>> - * triggered by WS0 will be ignored, then the second watch period starts;
>> - * when second timeout is reached, then WS1 is triggered, system reset.
>> + * When the first stage(the half timeout) is reached, WS0 interrupt is
>> + * triggered, at this moment the second watch period starts;
>> + * In the WS0 interrupt routine, panic will be triggered for saving the
>> + * system context.
>> + * If the system is getting into trouble and cannot be reset by panic or
>> + * restart properly by the kdump kernel(if supported), then the second
>> + * stage (the timeout) will be reached, system will be reset by WS1.
>>    *
>>    * More details about the hardware specification of this device:
>>    * ARM DEN0029B - Server Base System Architecture (SBSA)
>>    *
>>    * SBSA GWDT: |--------WOR-------WS0--------WOR-------WS1
>> - *            |----------------timeout----------------reset
>> + *            |--half_timeout--(panic)--half_timeout--reset
>>    *
>>    */
>>
>> @@ -84,6 +88,13 @@ MODULE_PARM_DESC(timeout,
>>                   "Watchdog timeout in seconds. (>=0, default="
>>                   __MODULE_STRING(DEFAULT_TIMEOUT) ")");
>>
>> +#ifdef CONFIG_ARM_SBSA_WATCHDOG_PANIC
>> +static bool panic_enabled = true;
>> +module_param(panic_enabled, bool, 0);
>> +MODULE_PARM_DESC(panic_enabled,
>> +                "enable panic at half timeout. (default=true)");
>> +#endif
>> +
>>   static bool nowayout = WATCHDOG_NOWAYOUT;
>>   module_param(nowayout, bool, S_IRUGO);
>>   MODULE_PARM_DESC(nowayout,
>> @@ -159,6 +170,16 @@ static int sbsa_gwdt_stop(struct watchdog_device *wdd)
>>          return 0;
>>   }
>>
>> +#ifdef CONFIG_ARM_SBSA_WATCHDOG_PANIC
>> +static irqreturn_t sbsa_gwdt_interrupt(int irq, void *dev_id)
>> +{
>> +       if (panic_enabled)
>> +               panic("SBSA Watchdog half timeout");
>> +
>> +       return IRQ_HANDLED;
>> +}
>> +#endif
>> +
>>   static struct watchdog_info sbsa_gwdt_info = {
>>          .identity       = "SBSA Generic Watchdog",
>>          .options        = WDIOF_SETTIMEOUT |
>> @@ -186,6 +207,9 @@ static int sbsa_gwdt_probe(struct platform_device *pdev)
>>          struct resource *res;
>>          u32 status;
>>          int ret;
>> +#ifdef CONFIG_ARM_SBSA_WATCHDOG_PANIC
>> +       int irq;
>> +#endif
>>
>>          gwdt = devm_kzalloc(dev, sizeof(*gwdt), GFP_KERNEL);
>>          if (!gwdt)
>> @@ -202,6 +226,14 @@ static int sbsa_gwdt_probe(struct platform_device *pdev)
>>          if (IS_ERR(rf_base))
>>                  return PTR_ERR(rf_base);
>>
>> +#ifdef CONFIG_ARM_SBSA_WATCHDOG_PANIC
>> +       irq = platform_get_irq(pdev, 0);
>> +       if (irq < 0) {
>> +               dev_err(dev, "unable to get ws0 interrupt.\n");
>> +               return irq;
>> +       }
>> +#endif
>> +
>
> Can't the driver revert to single stage mode if platform_get_irq()
> fails?  That way the value of 'irq' can be tested throughout the
> _probe() function and the #ifdefs removed.
>
Good point. Making irq support mandatory on all systems isn't really
a good idea.

Thanks,
Guenter

> Thanks,
> Mathieu
>
>>          /*
>>           * Get the frequency of system counter from the cp15 interface of ARM
>>           * Generic timer. We don't need to check it, because if it returns "0",
>> @@ -228,6 +260,14 @@ static int sbsa_gwdt_probe(struct platform_device *pdev)
>>                  dev_warn(dev, "System reset by WDT.\n");
>>                  wdd->bootstatus |= WDIOF_CARDRESET;
>>          }
>> +#ifdef CONFIG_ARM_SBSA_WATCHDOG_PANIC
>> +       ret = devm_request_irq(dev, irq, sbsa_gwdt_interrupt, 0,
>> +                              pdev->name, gwdt);
>> +       if (ret) {
>> +               dev_err(dev, "unable to request IRQ %d\n", irq);
>> +               return ret;
>> +       }
>> +#endif
>>
>>          ret = watchdog_register_device(wdd);
>>          if (ret)
>> @@ -242,6 +282,10 @@ static int sbsa_gwdt_probe(struct platform_device *pdev)
>>
>>          dev_info(dev, "Initialized with %ds timeout @ %u Hz%s\n", wdd->timeout,
>>                   gwdt->clk, status & SBSA_GWDT_WCS_EN ? " [enabled]" : "");
>> +#ifdef CONFIG_ARM_SBSA_WATCHDOG_PANIC
>> +       dev_info(dev, "Half timeout panic %s.\n",
>> +                panic_enabled ? "enabled" : "disabled");
>> +#endif
>>
>>          return 0;
>>   }
>> --
>> 2.5.0
>>
>