linux-kernel - Re: [PATCH v2 2/3] rtc: s3c: support for exynosautov9 on-chip RTC

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Message-ID: <20250903192046.GA4126@l14.localdomain>
Date: Wed, 3 Sep 2025 21:20:46 +0200
From: Henrik Grimler <henrik@...mler.se>
To: Devang Tailor <dev.tailor@...sung.com>
Cc: robh@...nel.org, krzk+dt@...nel.org, conor+dt@...nel.org,
	alim.akhtar@...sung.com, alexandre.belloni@...tlin.com,
	devicetree@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	linux-samsung-soc@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-rtc@...r.kernel.org, faraz.ata@...sung.com
Subject: Re: [PATCH v2 2/3] rtc: s3c: support for exynosautov9 on-chip RTC

Hi Devang,

On Thu, Jul 10, 2025 at 02:04:33PM +0530, Devang Tailor wrote:
> The on-chip RTC of this SoC is almost similar to the previous
> versions of SoC. Hence re-use the existing driver with platform specific
> change to enable RTC.

Could you please describe what the differences are to previous SoCs?
You write almost similar, please elaborate in what way in commit
message.

> This has been tested with 'hwclock' & 'date' utilities
> 
> Signed-off-by: Devang Tailor <dev.tailor@...sung.com>
> ---
> 
>  drivers/rtc/rtc-s3c.c | 18 ++++++++++++++++++
>  1 file changed, 18 insertions(+)
> 
> diff --git a/drivers/rtc/rtc-s3c.c b/drivers/rtc/rtc-s3c.c
> index 5dd575865adf..8db24b6360b8 100644
> --- a/drivers/rtc/rtc-s3c.c
> +++ b/drivers/rtc/rtc-s3c.c
> @@ -384,6 +384,15 @@ static void s3c6410_rtc_disable(struct s3c_rtc *info)
>  	writew(con, info->base + S3C2410_RTCCON);
>  }
>  
> +static void exynosautov9_rtc_disable(struct s3c_rtc *info)
> +{
> +	unsigned int con;
> +
> +	con = readb(info->base + S3C2410_RTCCON);
> +	con &= ~S3C2410_RTCCON_RTCEN;
> +	writeb(con, info->base + S3C2410_RTCCON);
> +}

Rather than adding a new rtc_disable variant I think this could be
handled in existing s3c24xx_rtc_disable (and I think that is what
Krzysztof meant). How about adding a new bool to rtc_data that
describes if S3C2410_TICNT reg is supported or not, and checking it in
s3c24xx_rtc_disable?

Best regards,
Henrik Grimler

>  static void s3c_rtc_remove(struct platform_device *pdev)
>  {
>  	struct s3c_rtc *info = platform_get_drvdata(pdev);
> @@ -574,6 +583,12 @@ static struct s3c_rtc_data const s3c6410_rtc_data = {
>  	.disable		= s3c6410_rtc_disable,
>  };
>  
> +static const struct s3c_rtc_data exynosautov9_rtc_data = {
> +	.irq_handler		= s3c6410_rtc_irq,
> +	.enable			= s3c24xx_rtc_enable,
> +	.disable		= exynosautov9_rtc_disable,
> +};
> +
>  static const __maybe_unused struct of_device_id s3c_rtc_dt_match[] = {
>  	{
>  		.compatible = "samsung,s3c2410-rtc",
> @@ -590,6 +605,9 @@ static const __maybe_unused struct of_device_id s3c_rtc_dt_match[] = {
>  	}, {
>  		.compatible = "samsung,exynos3250-rtc",
>  		.data = &s3c6410_rtc_data,
> +	}, {
> +		.compatible = "samsung,exynosautov9-rtc",
> +		.data = &exynosautov9_rtc_data,
>  	},
>  	{ /* sentinel */ },
>  };
> -- 
> 2.34.1
> 
>