On 01/20/2018 08:04 AM, PrasannaKumar Muralidharan wrote:
Hi Guenter,
On 20 January 2018 at 21:15, Guenter Roeck <linux@xxxxxxxxxxxx> wrote:
On 01/19/2018 11:31 PM, PrasannaKumar Muralidharan wrote:
Hi Paul,
On 30 December 2017 at 19:21, Paul Cercueil <paul@xxxxxxxxxxxxxxx> wrote:
The watchdog driver can restart the system by simply configuring the
hardware for a timeout of 0 seconds.
Signed-off-by: Paul Cercueil <paul@xxxxxxxxxxxxxxx>
Reviewed-by: Guenter Roeck <linux@xxxxxxxxxxxx>
---
drivers/watchdog/jz4740_wdt.c | 9 +++++++++
1 file changed, 9 insertions(+)
v2: No change
diff --git a/drivers/watchdog/jz4740_wdt.c
b/drivers/watchdog/jz4740_wdt.c
index 92d6ca8ceb49..fa7f49a3212c 100644
--- a/drivers/watchdog/jz4740_wdt.c
+++ b/drivers/watchdog/jz4740_wdt.c
@@ -130,6 +130,14 @@ static int jz4740_wdt_stop(struct watchdog_device
*wdt_dev)
return 0;
}
+static int jz4740_wdt_restart(struct watchdog_device *wdt_dev,
+ unsigned long action, void *data)
+{
+ wdt_dev->timeout = 0;
+ jz4740_wdt_start(wdt_dev);
+ return 0;
+}
+
static const struct watchdog_info jz4740_wdt_info = {
.options = WDIOF_SETTIMEOUT | WDIOF_KEEPALIVEPING |
WDIOF_MAGICCLOSE,
.identity = "jz4740 Watchdog",
@@ -141,6 +149,7 @@ static const struct watchdog_ops jz4740_wdt_ops = {
.stop = jz4740_wdt_stop,
.ping = jz4740_wdt_ping,
.set_timeout = jz4740_wdt_set_timeout,
+ .restart = jz4740_wdt_restart,
};
#ifdef CONFIG_OF
--
2.11.0
Noticed that min_timeout of the watchdog device is set to 1 but this
function calls start with timeout set to 0. Even though this works I
feel it is better to set min_timeout to 0.
No. That would be wrong. If you want to be pedantic, write a new function
__jz4740_wdt_set_timeout(u16 clock_div, u16 timeout_value) and call it
instead, but don't mess with min_timeout.
Guenter
What is the effect of changing min_timeout? I could see only
validation checks with it.
Let me ask you - you want to let userspace set a timeout of 0, which would
effectively reboot the system through the backdoor. Why ?
Guenter
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