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 3b3049c8c9e04ddb8ebfb3c391eba41b320286f3..5b5bc7dc3a1ccd38469867a30162caa7c6ee3c06 100644 (file)
--- a/drivers/rtc/rtc-ds1374.c
+++ b/drivers/rtc/rtc-ds1374.c
@@ -527,6 +527,10 @@ 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;
 
@@ -535,7 +539,8 @@ 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;