>On 4/9/21 8:11 PM, 王擎 wrote: >> >>> On 4/9/21 7:42 PM, 王擎 wrote: >>>> >>>>> On 4/9/21 2:55 AM, Wang Qing wrote: >>>>>> Use the bark interrupt as the pretimeout notifier if available. >>>>>> >>>>>> By default, the pretimeout notification shall occur one second earlier >>>>>> than the timeout. >>>>>> >>>>>> Signed-off-by: Wang Qing <wangqing@xxxxxxxx> >>>>>> --- >>>>>> drivers/watchdog/mtk_wdt.c | 47 +++++++++++++++++++++++++++++++++++++++++++--- >>>>>> 1 file changed, 44 insertions(+), 3 deletions(-) >>>>>> >>>>>> diff --git a/drivers/watchdog/mtk_wdt.c b/drivers/watchdog/mtk_wdt.c >>>>>> index 97ca993..8b919cc >>>>>> --- a/drivers/watchdog/mtk_wdt.c >>>>>> +++ b/drivers/watchdog/mtk_wdt.c >>>>>> @@ -25,6 +25,7 @@ >>>>>> #include <linux/reset-controller.h> >>>>>> #include <linux/types.h> >>>>>> #include <linux/watchdog.h> >>>>>> +#include <linux/interrupt.h> >>>>>> >>>>>> #define WDT_MAX_TIMEOUT 31 >>>>>> #define WDT_MIN_TIMEOUT 1 >>>>>> @@ -234,18 +235,35 @@ static int mtk_wdt_start(struct watchdog_device *wdt_dev) >>>>>> void __iomem *wdt_base = mtk_wdt->wdt_base; >>>>>> int ret; >>>>>> >>>>>> - ret = mtk_wdt_set_timeout(wdt_dev, wdt_dev->timeout); >>>>>> + ret = mtk_wdt_set_timeout(wdt_dev, wdt_dev->timeout - wdt_dev->pretimeout); >>>>> >>>>> That looks suspiciously like the real watchdog won't happen at all. >>>>> What will happen if the pretimeout governor is set to none ? >>>>> >>>>> Guenter >>>>> >>>> The pretimeout governor is panic by default. If pretimeout is enabled and the governor is >>>> set to none, it means the timeout behavior does not need to be processed, only printing. >>>> >>> >>> That was not my question. My question was if the real timeout happens in that case. >>> >>> Guenter >>> >> Yes, the real timeout will happen. After WDT timeout, IRQ is sent out instead of >> reset signal first. In order to ensure that CPU does not get stuck after IRQ is sent out, >> WDT will time again and send reset signal to reset. >> > >When will that be, or in other words how does the chip know when to time out ? >After all, only a single timeout value is written into the chip. I don't see how >it would know to reset the chip after wdt_dev->timeout. > >Guenter > > Sorry I made a mistake, the IRQ is sent out first, then time again and reset only when WDT_MODE_IRQ_EN|WDT_MODE_DUAL_EN is enabled. WDT_MODE_DUAL_EN mode is a special mode, depending on the specific chip design. If WDT_MODE_IRQ_EN|~WDT_MODE_DUAL_EN as described in my patch, it just sent out IRQ instead of reset signal, the real timeout will not happen if the pretimeout governor is set to none. Also, ~(WDT_MODE_IRQ_EN | WDT_MODE_DUAL_EN) means send reset signal directly. It does not support pretimeout processing. Thanks Qing Wang
