linux-kernel - Re: [PATCH v1] watchdog: meson: keep running if already active

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Message-ID: <f756b2d5-56e7-6e52-2739-eca4bb33508b@baylibre.com>
Date:   Tue, 5 Jul 2022 16:39:59 +0200
From:   Neil Armstrong <narmstrong@...libre.com>
To:     Philippe Boos <pboos@...libre.com>,
        Wim Van Sebroeck <wim@...ux-watchdog.org>,
        Guenter Roeck <linux@...ck-us.net>
Cc:     Kevin Hilman <khilman@...libre.com>,
        Jerome Brunet <jbrunet@...libre.com>,
        Martin Blumenstingl <martin.blumenstingl@...glemail.com>,
        linux-watchdog@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-amlogic@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1] watchdog: meson: keep running if already active

Hi,

On 05/07/2022 16:24, 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 then restart the watchdog if it was
> previously active.
> 
> Reviewed-by: Jerome Brunet <jbrunet@...libre.com>

Please drop this review tag since it was done off-list

> Signed-off-by: Philippe Boos <pboos@...libre.com>
> ---
>   drivers/watchdog/meson_gxbb_wdt.c | 10 ++++++++++
>   1 file changed, 10 insertions(+)
> 
> diff --git a/drivers/watchdog/meson_gxbb_wdt.c b/drivers/watchdog/meson_gxbb_wdt.c
> index 5a9ca10fbcfa..8c2c6f7f3bb5 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 regval;
>   
>   	data = devm_kzalloc(dev, sizeof(*data), GFP_KERNEL);
>   	if (!data)
> @@ -177,6 +178,8 @@ static int meson_gxbb_wdt_probe(struct platform_device *pdev)
>   	data->wdt_dev.timeout = DEFAULT_TIMEOUT;
>   	watchdog_set_drvdata(&data->wdt_dev, data);
>   
> +	regval = readl(data->reg_base + GXBB_WDT_CTRL_REG); > +
>   	/* Setup with 1ms timebase */
>   	writel(((clk_get_rate(data->clk) / 1000) & GXBB_WDT_CTRL_DIV_MASK) |
>   		GXBB_WDT_CTRL_EE_RESET |
> @@ -186,6 +189,13 @@ static int meson_gxbb_wdt_probe(struct platform_device *pdev)
>   
>   	meson_gxbb_wdt_set_timeout(&data->wdt_dev, data->wdt_dev.timeout);
>   
> +	if ((regval & GXBB_WDT_CTRL_EN) != 0) {
> +		ret = meson_gxbb_wdt_start(&data->wdt_dev);
> +		if (ret)
> +			return ret;
> +		set_bit(WDOG_HW_RUNNING, &data->wdt_dev.status);
> +	}
> +
>   	watchdog_stop_on_reboot(&data->wdt_dev);
>   	return devm_watchdog_register_device(dev, &data->wdt_dev);
>   }

I think it would be much claner to leave the watchdog enabled, and get the parameters
from the registers and update the wdt_dev accordingly.

Neil