linux-kernel - [PATCH v3] watchdog: qcom_wdt: set WDOG_HW

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Date:   Sat, 31 Oct 2020 12:52:14 +0100
From:   Robert Marko <robert.marko@...tura.hr>
To:     agross@...nel.org, bjorn.andersson@...aro.org,
        wim@...ux-watchdog.org, linux@...ck-us.net,
        linux-arm-msm@...r.kernel.org, linux-watchdog@...r.kernel.org,
        linux-kernel@...r.kernel.org
Cc:     Robert Marko <robert.marko@...tura.hr>,
        Luka Perkov <luka.perkov@...tura.hr>
Subject: [PATCH v3] watchdog: qcom_wdt: set WDOG_HW_RUNNING bit when appropriate

If the watchdog hardware is enabled/running during boot, e.g.
due to a boot loader configuring it, we must tell the
watchdog framework about this fact so that it can ping the
watchdog until userspace opens the device and takes over
control.

Do so using the WDOG_HW_RUNNING flag that exists for exactly
that use-case.

Signed-off-by: Robert Marko <robert.marko@...tura.hr>
Cc: Luka Perkov <luka.perkov@...tura.hr>
---
Changes in v3:
* Drop call to stop as start already does it
* Update commit message

Changes in v2:
* Correct authorship

 drivers/watchdog/qcom-wdt.c | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/drivers/watchdog/qcom-wdt.c b/drivers/watchdog/qcom-wdt.c
index ab7465d186fd..64f44a4b7eb8 100644
--- a/drivers/watchdog/qcom-wdt.c
+++ b/drivers/watchdog/qcom-wdt.c
@@ -152,6 +152,13 @@ static int qcom_wdt_restart(struct watchdog_device *wdd, unsigned long action,
 	return 0;
 }
 
+static int qcom_wdt_is_running(struct watchdog_device *wdd)
+{
+	struct qcom_wdt *wdt = to_qcom_wdt(wdd);
+
+	return (readl(wdt_addr(wdt, WDT_EN)) & 1);
+}
+
 static const struct watchdog_ops qcom_wdt_ops = {
 	.start		= qcom_wdt_start,
 	.stop		= qcom_wdt_stop,
@@ -294,6 +301,17 @@ static int qcom_wdt_probe(struct platform_device *pdev)
 	wdt->wdd.timeout = min(wdt->wdd.max_timeout, 30U);
 	watchdog_init_timeout(&wdt->wdd, 0, dev);
 
+	/*
+	 * If WDT is already running, call WDT start which
+	 * will stop the WDT, set timeouts as bootloader
+	 * might use different ones and set running bit
+	 * to inform the WDT subsystem to ping the WDT
+	 */
+	if (qcom_wdt_is_running(&wdt->wdd)) {
+		qcom_wdt_start(&wdt->wdd);
+		set_bit(WDOG_HW_RUNNING, &wdt->wdd.status);
+	}
+
 	ret = devm_watchdog_register_device(dev, &wdt->wdd);
 	if (ret)
 		return ret;
-- 
2.28.0