linux-kernel - [PATCH v2] watchdog: meson: keep running if already active

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Message-Id: <20220801092150.4449-1-pboos@baylibre.com>
Date:   Mon,  1 Aug 2022 11:21:50 +0200
From:   Philippe Boos <pboos@...libre.com>
To:     Wim Van Sebroeck <wim@...ux-watchdog.org>,
        Guenter Roeck <linux@...ck-us.net>,
        Neil Armstrong <narmstrong@...libre.com>
Cc:     Philippe Boos <pboos@...libre.com>,
        Kevin Hilman <khilman@...libre.com>,
        Jerome Brunet <jbrunet@...libre.com>,
        Martin Blumenstingl <martin.blumenstingl@...glemail.com>,
        linux-watchdog@...r.kernel.org (open list:WATCHDOG DEVICE DRIVERS),
        linux-arm-kernel@...ts.infradead.org (moderated list:ARM/Amlogic Meson
        SoC support),
        linux-amlogic@...ts.infradead.org (open list:ARM/Amlogic Meson SoC
        support), linux-kernel@...r.kernel.org (open list)
Subject: [PATCH v2] watchdog: meson: keep running if already active

If the watchdog is already running (e.g.: started by bootloader) then
the kernel driver should keep the watchdog active but the amlogic driver
turns it off.

Let the driver fix the clock rate if already active because we do not
know the previous timebase value. To avoid unintentional resetting we
temporarily set it to its maximum value.

Then keep the enable bit if is was previously active.

Signed-off-by: Philippe Boos <pboos@...libre.com>
---
 drivers/watchdog/meson_gxbb_wdt.c | 24 +++++++++++++++++++-----
 1 file changed, 19 insertions(+), 5 deletions(-)

diff --git a/drivers/watchdog/meson_gxbb_wdt.c b/drivers/watchdog/meson_gxbb_wdt.c
index 5a9ca10fbcfa..8be8fd9e5637 100644
--- a/drivers/watchdog/meson_gxbb_wdt.c
+++ b/drivers/watchdog/meson_gxbb_wdt.c
@@ -146,6 +146,7 @@ static int meson_gxbb_wdt_probe(struct platform_device *pdev)
 	struct device *dev = &pdev->dev;
 	struct meson_gxbb_wdt *data;
 	int ret;
+	u32 ctrl_reg;
 
 	data = devm_kzalloc(dev, sizeof(*data), GFP_KERNEL);
 	if (!data)
@@ -177,13 +178,26 @@ static int meson_gxbb_wdt_probe(struct platform_device *pdev)
 	data->wdt_dev.timeout = DEFAULT_TIMEOUT;
 	watchdog_set_drvdata(&data->wdt_dev, data);
 
+	ctrl_reg = readl(data->reg_base + GXBB_WDT_CTRL_REG) &
+				GXBB_WDT_CTRL_EN;
+
+	if (ctrl_reg) {
+		/* Watchdog is running - keep it running but extend timeout
+		 * to the maximum while setting the timebase
+		 */
+		set_bit(WDOG_HW_RUNNING, &data->wdt_dev.status);
+		meson_gxbb_wdt_set_timeout(&data->wdt_dev,
+				GXBB_WDT_TCNT_SETUP_MASK / 1000);
+	}
+
 	/* Setup with 1ms timebase */
-	writel(((clk_get_rate(data->clk) / 1000) & GXBB_WDT_CTRL_DIV_MASK) |
-		GXBB_WDT_CTRL_EE_RESET |
-		GXBB_WDT_CTRL_CLK_EN |
-		GXBB_WDT_CTRL_CLKDIV_EN,
-		data->reg_base + GXBB_WDT_CTRL_REG);
+	ctrl_reg |= ((clk_get_rate(data->clk) / 1000) &
+			GXBB_WDT_CTRL_DIV_MASK) |
+			GXBB_WDT_CTRL_EE_RESET |
+			GXBB_WDT_CTRL_CLK_EN |
+			GXBB_WDT_CTRL_CLKDIV_EN;
 
+	writel(ctrl_reg, data->reg_base + GXBB_WDT_CTRL_REG);
 	meson_gxbb_wdt_set_timeout(&data->wdt_dev, data->wdt_dev.timeout);
 
 	watchdog_stop_on_reboot(&data->wdt_dev);
-- 
2.20.1