linux-kernel - Re: [PATCH 5/7] watchdog: s3c2410: Introduce separate source clock

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Date:   Thu, 28 Oct 2021 17:21:20 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     Sam Protsenko <semen.protsenko@...aro.org>,
        Wim Van Sebroeck <wim@...ux-watchdog.org>,
        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: Re: [PATCH 5/7] watchdog: s3c2410: Introduce separate source clock

On 10/28/21 11:35 AM, Sam Protsenko wrote:
> Some Exynos chips (like Exynos850) have dedicated source clock. That
> clock is provided from device tree as "watchdog_src" clock. In such
> case, "watchdog" clock is just a peripheral clock used for register
> interface. If "watchdog_src" is present, use its rate instead of
> "watchdog" for all timer related calculations.
> 

If the "watchdog_src" clock is present, is "watchdog" clock still needed ?
Please state that explicitly, since it is kind of unusual.

Guenter

> Signed-off-by: Sam Protsenko <semen.protsenko@...aro.org>
> ---
>   drivers/watchdog/s3c2410_wdt.c | 33 +++++++++++++++++++++++++++------
>   1 file changed, 27 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/watchdog/s3c2410_wdt.c b/drivers/watchdog/s3c2410_wdt.c
> index a5ef7171a90e..bfc5872ca497 100644
> --- a/drivers/watchdog/s3c2410_wdt.c
> +++ b/drivers/watchdog/s3c2410_wdt.c
> @@ -126,6 +126,8 @@ struct s3c2410_wdt_variant {
>   struct s3c2410_wdt {
>   	struct device		*dev;
>   	struct clk		*clock;
> +	struct clk		*clock_src;
> +	unsigned long		freq_src;
>   	void __iomem		*reg_base;
>   	unsigned int		count;
>   	spinlock_t		lock;
> @@ -213,10 +215,8 @@ MODULE_DEVICE_TABLE(platform, s3c2410_wdt_ids);
>   
>   /* functions */
>   
> -static inline unsigned int s3c2410wdt_max_timeout(struct clk *clock)
> +static inline unsigned int s3c2410wdt_max_timeout(unsigned long freq)
>   {
> -	unsigned long freq = clk_get_rate(clock);
> -
>   	return S3C2410_WTCNT_MAXCNT / (freq / (S3C2410_WTCON_PRESCALE_MAX + 1)
>   				       / S3C2410_WTCON_MAXDIV);
>   }
> @@ -364,7 +364,7 @@ static int s3c2410wdt_set_heartbeat(struct watchdog_device *wdd,
>   				    unsigned int timeout)
>   {
>   	struct s3c2410_wdt *wdt = watchdog_get_drvdata(wdd);
> -	unsigned long freq = clk_get_rate(wdt->clock);
> +	unsigned long freq = wdt->freq_src;
>   	unsigned int count;
>   	unsigned int divisor = 1;
>   	unsigned long wtcon;
> @@ -627,13 +627,27 @@ static int s3c2410wdt_probe(struct platform_device *pdev)
>   		return ret;
>   	}
>   
> +	/* "watchdog_src" clock is optional; if it's not present -- just skip */
> +	wdt->clock_src = devm_clk_get(dev, "watchdog_src");
> +	if (!IS_ERR(wdt->clock_src)) {
> +		ret = clk_prepare_enable(wdt->clock_src);
> +		if (ret < 0) {
> +			dev_err(dev, "failed to enable source clock\n");
> +			ret = PTR_ERR(wdt->clock_src);
> +			goto err_clk;
> +		}
> +		wdt->freq_src = clk_get_rate(wdt->clock_src);
> +	} else {
> +		wdt->freq_src = clk_get_rate(wdt->clock);
> +	}
> +
>   	wdt->wdt_device.min_timeout = 1;
> -	wdt->wdt_device.max_timeout = s3c2410wdt_max_timeout(wdt->clock);
> +	wdt->wdt_device.max_timeout = s3c2410wdt_max_timeout(wdt->freq_src);
>   
>   	ret = s3c2410wdt_cpufreq_register(wdt);
>   	if (ret < 0) {
>   		dev_err(dev, "failed to register cpufreq\n");
> -		goto err_clk;
> +		goto err_clk_src;
>   	}
>   
>   	watchdog_set_drvdata(&wdt->wdt_device, wdt);
> @@ -707,6 +721,10 @@ static int s3c2410wdt_probe(struct platform_device *pdev)
>    err_cpufreq:
>   	s3c2410wdt_cpufreq_deregister(wdt);
>   
> + err_clk_src:
> +	if (!IS_ERR(wdt->clock_src))
> +		clk_disable_unprepare(wdt->clock_src);
> +
>    err_clk:
>   	clk_disable_unprepare(wdt->clock);
>   
> @@ -727,6 +745,9 @@ static int s3c2410wdt_remove(struct platform_device *dev)
>   
>   	s3c2410wdt_cpufreq_deregister(wdt);
>   
> +	if (!IS_ERR(wdt->clock_src))
> +		clk_disable_unprepare(wdt->clock_src);
> +
>   	clk_disable_unprepare(wdt->clock);
>   
>   	return 0;
>