Re: [PATCH 7/7] watchdog: s3c2410: Let kernel kick watchdog

From: Guenter Roeck
Date: Thu Oct 28 2021 - 20:31:00 EST


On 10/28/21 11:35 AM, Sam Protsenko wrote:
When "tmr_atboot" module param is set, the watchdog is started in
driver's probe. In that case, also set WDOG_HW_RUNNING bit to let
watchdog core driver know it's running. This way wathcdog core can kick
the watchdog for us (if CONFIG_WATCHDOG_HANDLE_BOOT_ENABLED option is
enabled), until user space takes control.

Signed-off-by: Sam Protsenko <semen.protsenko@xxxxxxxxxx>
---
drivers/watchdog/s3c2410_wdt.c | 26 +++++++++++++++-----------
1 file changed, 15 insertions(+), 11 deletions(-)

diff --git a/drivers/watchdog/s3c2410_wdt.c b/drivers/watchdog/s3c2410_wdt.c
index ca082b1226e3..9af014ff1468 100644
--- a/drivers/watchdog/s3c2410_wdt.c
+++ b/drivers/watchdog/s3c2410_wdt.c
@@ -732,6 +732,21 @@ static int s3c2410wdt_probe(struct platform_device *pdev)
wdt->wdt_device.bootstatus = s3c2410wdt_get_bootstatus(wdt);
wdt->wdt_device.parent = dev;
+ /*
+ * If "tmr_atboot" param is non-zero, start the watchdog right now. Also
+ * set WDOG_HW_RUNNING bit, so that watchdog core can kick the watchdog.
+ *
+ * If we're not enabling the watchdog, then ensure it is disabled if it
+ * has been left running from the bootloader or other source.
+ */
+ if (tmr_atboot && started == 0) {
+ dev_info(dev, "starting watchdog timer\n");
+ s3c2410wdt_start(&wdt->wdt_device);
+ set_bit(WDOG_HW_RUNNING, &wdt->wdt_device.status);
+ } else if (!tmr_atboot) {
+ s3c2410wdt_stop(&wdt->wdt_device);
+ }
+

This doesn't cover the case where the watchdog is already enabled by the BIOS.
In that case, WDOG_HW_RUNNING won't be set, and the watchdog will time out
if the userspace handler is not loaded fast enough. The code should consistently
set WDOG_HW_RUNNING if the watchdog is running.

Guenter

ret = watchdog_register_device(&wdt->wdt_device);
if (ret)
goto err_cpufreq;
@@ -740,17 +755,6 @@ static int s3c2410wdt_probe(struct platform_device *pdev)
if (ret < 0)
goto err_unregister;
- if (tmr_atboot && started == 0) {
- dev_info(dev, "starting watchdog timer\n");
- s3c2410wdt_start(&wdt->wdt_device);
- } else if (!tmr_atboot) {
- /* if we're not enabling the watchdog, then ensure it is
- * disabled if it has been left running from the bootloader
- * or other source */
-
- s3c2410wdt_stop(&wdt->wdt_device);
- }
-
platform_set_drvdata(pdev, wdt);
/* print out a statement of readiness */