linux-kernel - Re: [PATCH v2 10/12] watchdog: s3c2410: Support separate source clock

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Message-ID: <a63f37a9-ea04-2606-e4f5-1170c4e59db2@canonical.com>
Date:   Tue, 2 Nov 2021 11:15:40 +0100
From:   Krzysztof Kozlowski <krzysztof.kozlowski@...onical.com>
To:     Sam Protsenko <semen.protsenko@...aro.org>,
        Wim Van Sebroeck <wim@...ux-watchdog.org>,
        Guenter Roeck <linux@...ck-us.net>,
        Rob Herring <robh+dt@...nel.org>
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 v2 10/12] watchdog: s3c2410: Support separate source clock

On 31/10/2021 13:22, Sam Protsenko wrote:
> Right now all devices supported in the driver have the single clock: it
> acts simultaneously as a bus clock (providing register interface
> clocking) and source clock (driving watchdog counter). Some newer Exynos
> chips, like Exynos850, have two separate clocks for that. In that case
> two clocks will be passed to the driver from the resource provider, e.g.
> Device Tree. Provide necessary infrastructure to support that case:
>   - use source clock's rate for all timer related calculations
>   - use bus clock to gate/ungate the register interface
> 
> All devices that use the single clock are kept intact: if only one clock
> is passed from Device Tree, it will be used for both purposes as before.
> 
> Signed-off-by: Sam Protsenko <semen.protsenko@...aro.org>
> ---
> Changes in v2:
>   - Reworded commit message to be more formal
>   - Used separate "has_src_clk" trait to tell if source clock is present
>   - Renamed clock variables to match their purpose
>   - Removed caching source clock rate, obtaining it in place each time instead
>   - Renamed err labels for more consistency
> 
>  drivers/watchdog/s3c2410_wdt.c | 52 +++++++++++++++++++++++++---------
>  1 file changed, 39 insertions(+), 13 deletions(-)
> 
> diff --git a/drivers/watchdog/s3c2410_wdt.c b/drivers/watchdog/s3c2410_wdt.c
> index fdb1a1e9bd04..c733917c5470 100644
> --- a/drivers/watchdog/s3c2410_wdt.c
> +++ b/drivers/watchdog/s3c2410_wdt.c
> @@ -118,7 +118,9 @@ struct s3c2410_wdt_variant {
>  
>  struct s3c2410_wdt {
>  	struct device		*dev;
> -	struct clk		*clock;
> +	struct clk		*bus_clk; /* for register interface (PCLK) */
> +	struct clk		*src_clk; /* for WDT counter */
> +	bool			has_src_clk;

Why do you need the has_src_clk value? If clk_get() fails, just store
there NULL and clk API will handle it.

Best regards,
Krzysztof