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

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Message-ID: <20220925154022.GA1758351@roeck-us.net>
Date:   Sun, 25 Sep 2022 08:40:22 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     Philippe Boos <pboos@...libre.com>
Cc:     Wim Van Sebroeck <wim@...ux-watchdog.org>,
        Neil Armstrong <narmstrong@...libre.com>,
        Kevin Hilman <khilman@...libre.com>,
        Jerome Brunet <jbrunet@...libre.com>,
        Martin Blumenstingl <martin.blumenstingl@...glemail.com>,
        "open list:WATCHDOG DEVICE DRIVERS" <linux-watchdog@...r.kernel.org>,
        "moderated list:ARM/Amlogic Meson SoC support" 
        <linux-arm-kernel@...ts.infradead.org>,
        "open list:ARM/Amlogic Meson SoC support" 
        <linux-amlogic@...ts.infradead.org>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] watchdog: meson: keep running if already active

On Mon, Aug 01, 2022 at 11:21:50AM +0200, Philippe Boos wrote:
> 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>
> Reviewed-by: Jerome Brunet <jbrunet@...libre.com>

Reviewed-by: Guenter Roeck <linux@...ck-us.net>

> ---
>  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);