linux-kernel - [PATCH v2 04/12] watchdog: s3c2410: Let kernel kick watchdog

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Date:   Sun, 31 Oct 2021 14:22:08 +0200
From:   Sam Protsenko <semen.protsenko@...aro.org>
To:     Wim Van Sebroeck <wim@...ux-watchdog.org>,
        Guenter Roeck <linux@...ck-us.net>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski@...onical.com>
Cc:     linux-watchdog@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-samsung-soc@...r.kernel.org
Subject: [PATCH v2 04/12] watchdog: s3c2410: Let kernel kick watchdog

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 watchdog core can kick
the watchdog for us (if CONFIG_WATCHDOG_HANDLE_BOOT_ENABLED option is
enabled), until user space takes control.

WDOG_HW_RUNNING bit must be set before registering the watchdog. So the
"tmr_atboot" handling code is moved before watchdog registration, to
avoid performing the same check twice. This is also logical because
WDOG_HW_RUNNING bit makes WDT core expect actually running watchdog.

Signed-off-by: Sam Protsenko <semen.protsenko@...aro.org>
---
Changes in v2:
  - Added explanation on moving the code block to commit message
  - [PATCH 03/12] handles the case when tmr_atboot is present but valid
    timeout wasn't found

 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 00421cf22556..0845c05034a1 100644
--- a/drivers/watchdog/s3c2410_wdt.c
+++ b/drivers/watchdog/s3c2410_wdt.c
@@ -604,6 +604,21 @@ 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) {
+		dev_info(dev, "starting watchdog timer\n");
+		s3c2410wdt_start(&wdt->wdt_device);
+		set_bit(WDOG_HW_RUNNING, &wdt->wdt_device.status);
+	} else {
+		s3c2410wdt_stop(&wdt->wdt_device);
+	}
+
 	ret = watchdog_register_device(&wdt->wdt_device);
 	if (ret)
 		goto err_cpufreq;
@@ -612,17 +627,6 @@ static int s3c2410wdt_probe(struct platform_device *pdev)
 	if (ret < 0)
 		goto err_unregister;
 
-	if (tmr_atboot) {
-		dev_info(dev, "starting watchdog timer\n");
-		s3c2410wdt_start(&wdt->wdt_device);
-	} else {
-		/* 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 */
-- 
2.30.2