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SubjectRe: [PATCH 2/2] watchdog: dw_wdt: add restart handler support
On 09/19/2014 08:07 PM, Guenter Roeck wrote:
> On 09/18/2014 11:29 PM, Jisheng Zhang wrote:
>> The kernel core now provides an API to trigger a system restart.
>> Register with it to support restarting the system via. watchdog.
>>
>> Signed-off-by: Jisheng Zhang <jszhang@marvell.com>
>> ---
>> drivers/watchdog/dw_wdt.c | 27 +++++++++++++++++++++++++++
>> 1 file changed, 27 insertions(+)
>>
>> diff --git a/drivers/watchdog/dw_wdt.c b/drivers/watchdog/dw_wdt.c
>> index ad0619d..4ca41e9 100644
>> --- a/drivers/watchdog/dw_wdt.c
>> +++ b/drivers/watchdog/dw_wdt.c
>> @@ -29,9 +29,11 @@
>> #include <linux/miscdevice.h>
>> #include <linux/module.h>
>> #include <linux/moduleparam.h>
>> +#include <linux/notifier.h>
>> #include <linux/of.h>
>> #include <linux/pm.h>
>> #include <linux/platform_device.h>
>> +#include <linux/reboot.h>
>> #include <linux/spinlock.h>
>> #include <linux/timer.h>
>> #include <linux/uaccess.h>
>> @@ -62,6 +64,7 @@ static struct {
>> unsigned long next_heartbeat;
>> struct timer_list timer;
>> int expect_close;
>> + struct notifier_block restart_handler;
>> } dw_wdt;
>>
>> static inline int dw_wdt_is_enabled(void)
>> @@ -119,6 +122,22 @@ static void dw_wdt_keepalive(void)
>> WDOG_COUNTER_RESTART_REG_OFFSET);
>> }
>>
>> +static int dw_wdt_restart_handle(struct notifier_block *this,
>> + unsigned long mode, void *cmd)
>> +{
>> + u32 val;
>> +
>> + writel(0, dw_wdt.regs + WDOG_TIMEOUT_RANGE_REG_OFFSET);
>> + val = readl(dw_wdt.regs + WDOG_CONTROL_REG_OFFSET);
>> + if (val & WDOG_CONTROL_REG_WDT_EN_MASK)
>> + writel(WDOG_COUNTER_RESTART_KICK_VALUE, dw_wdt.regs +
>> + WDOG_COUNTER_RESTART_REG_OFFSET);
>> + else
>> + writel(WDOG_CONTROL_REG_WDT_EN_MASK,
>> + dw_wdt.regs + WDOG_CONTROL_REG_OFFSET);
>
> Don't you have to write WDOG_COUNTER_RESTART_KICK_VALUE into
> WDOG_COUNTER_RESTART_REG_OFFSET in the else case as well ?
>

According to the datasheet, it should be sufficient to
- Write 0 into WDOG_TIMEOUT_RANGE_REG_OFFSET to select the minimum timeout period
- Write 0x1 into WDOG_CONTROL_REG_OFFSET to enable the watchdog and select reset
as desired action. This can be unconditional.

Writing into the restart register should not be necessary.

Thanks,
Guenter



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