rtc: ds1374: wdt: Fix issue with timeout scaling from secs to wdt ticks
[ Upstream commit 453d0744f6c6ca3f9749b8c57c2e85b5b9f52514 ]
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 <mdf@kernel.org>
Signed-off-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
diff --git a/drivers/rtc/rtc-ds1374.c b/drivers/rtc/rtc-ds1374.c
index 3b3049c..5b5bc7d 100644
--- a/drivers/rtc/rtc-ds1374.c
+++ b/drivers/rtc/rtc-ds1374.c
@@ -527,6 +527,10 @@
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;
@@ -535,7 +539,8 @@
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;