From 453d0744f6c6ca3f9749b8c57c2e85b5b9f52514 Mon Sep 17 00:00:00 2001 From: Moritz Fischer Date: Mon, 24 Apr 2017 15:05:11 -0700 Subject: [PATCH] rtc: ds1374: wdt: Fix issue with timeout scaling from secs to wdt ticks The issue is that the internal counter that triggers the watchdog reset is actually running at 4096 Hz instead of 1Hz, therefore the value given by userland (in sec) needs to be multiplied by 4096 to get the correct behavior. Fixes: 920f91e50c5b ("drivers/rtc/rtc-ds1374.c: add watchdog support") Signed-off-by: Moritz Fischer Signed-off-by: Alexandre Belloni --- drivers/rtc/rtc-ds1374.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) diff --git a/drivers/rtc/rtc-ds1374.c b/drivers/rtc/rtc-ds1374.c index 4cd115e..2a8b5b3 100644 --- a/drivers/rtc/rtc-ds1374.c +++ b/drivers/rtc/rtc-ds1374.c @@ -525,6 +525,10 @@ static long ds1374_wdt_ioctl(struct file *file, unsigned int cmd, if (get_user(new_margin, (int __user *)arg)) return -EFAULT; + /* the hardware's tick rate is 4096 Hz, so + * the counter value needs to be scaled accordingly + */ + new_margin <<= 12; if (new_margin < 1 || new_margin > 16777216) return -EINVAL; @@ -533,7 +537,8 @@ static long ds1374_wdt_ioctl(struct file *file, unsigned int cmd, ds1374_wdt_ping(); /* fallthrough */ case WDIOC_GETTIMEOUT: - return put_user(wdt_margin, (int __user *)arg); + /* when returning ... inverse is true */ + return put_user((wdt_margin >> 12), (int __user *)arg); case WDIOC_SETOPTIONS: if (copy_from_user(&options, (int __user *)arg, sizeof(int))) return -EFAULT; -- 2.7.4