Re: [PATCH v3 1/3] rtc: cv1800b: Add seconds counter support

[Yao Zi <me@ziyao.cc>]

On Wed, Oct 07, 2026 at 11:33:05AM +0800, Zhuxu Ran wrote:
> Add a driver for the CV1800B RTC seconds counter described by the
> upstream devicetree. Map the node's register range, enable the RTC
> clock, and implement reading and setting the 32-bit counter. Bind
> the existing sysreset driver as a child when enabled.
> 
> Adapt the register definitions and seconds-counter sequence from
> Linux drivers/rtc/rtc-cv1800.c by Jingbao Qiu.
> 
> Link: https://git.kernel.org/linus/d9f82683b123ce315cc36c4b20a5bc3d8644f947
> 
> Signed-off-by: Zhuxu Ran <zhuxu_ran@zohomail.com>
> ---
>  drivers/rtc/Kconfig   |   9 ++++
>  drivers/rtc/Makefile  |   1 +
>  drivers/rtc/cv1800b.c | 123 ++++++++++++++++++++++++++++++++++++++++++++++++++
>  3 files changed, 133 insertions(+)

...

> diff --git a/drivers/rtc/Makefile b/drivers/rtc/Makefile
> index 742481ce185..3c480156498 100644
> --- a/drivers/rtc/Makefile
> +++ b/drivers/rtc/Makefile
> @@ -7,6 +7,7 @@
>  obj-$(CONFIG_$(PHASE_)DM_RTC) += rtc-uclass.o
>  
>  obj-$(CONFIG_RTC_ARMADA38X) += armada38x.o
> +obj-$(CONFIG_RTC_CV1800B) += cv1800b.o
>  obj-$(CONFIG_RTC_DAVINCI) += davinci.o
>  obj-$(CONFIG_RTC_DS1307) += ds1307.o
>  obj-$(CONFIG_RTC_DS1337) += ds1337.o
> diff --git a/drivers/rtc/cv1800b.c b/drivers/rtc/cv1800b.c
> new file mode 100644
> index 00000000000..e98efb319d7
> --- /dev/null
> +++ b/drivers/rtc/cv1800b.c
> @@ -0,0 +1,123 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * Copyright (C) 2026 Zhuxu Ran <zhuxu_ran@zohomail.com>
> + *
> + * Based on the Linux driver by Jingbao Qiu <qiujingbao.dlmu@gmail.com>.

If so, it would be good to keep the copyright line :)

> + */

...

> +struct cv1800b_rtc_priv {
> +	struct regmap *regmap;
> +	struct clk clk;

I don't think you make use of clk anymore after exiting probe(), so I
think it makes sense to turn it into a local variable.

> +};
> +
> +static int cv1800b_rtc_get(struct udevice *dev, struct rtc_time *time)
> +{
> +	struct cv1800b_rtc_priv *priv = dev_get_priv(dev);
> +	u32 value;
> +	int ret;
> +
> +	ret = regmap_read(priv->regmap, SEC_PULSE_GEN, &value);
> +	if (ret)
> +		return ret;
> +	if (value & SEL_SEC_PULSE)
> +		return -EINVAL;
> +
> +	ret = regmap_read(priv->regmap, SEC_CNTR_VAL, &value);
> +	if (ret)
> +		return ret;
> +
> +	rtc_to_tm(value, time);
> +
> +	return 0;
> +}
> +
> +static int cv1800b_rtc_set(struct udevice *dev, const struct rtc_time *time)
> +{
> +	struct cv1800b_rtc_priv *priv = dev_get_priv(dev);
> +	time64_t seconds;
> +	int ret;
> +
> +	if (time->tm_year < 1970)
> +		return -EINVAL;
> +
> +	seconds = rtc_mktime(time);
> +	if (seconds < 0 || seconds > U32_MAX)
> +		return -ERANGE;
> +
> +	ret = regmap_write(priv->regmap, SET_SEC_CNTR_VAL, seconds);
> +	if (ret)
> +		return ret;
> +
> +	ret = regmap_write(priv->regmap, SET_SEC_CNTR_TRIG, 1);
> +	if (ret)
> +		return ret;
> +
> +	ret = regmap_write(priv->regmap, MACRO_RG_SET_T, seconds);
> +	if (ret)
> +		return ret;
> +
> +	return regmap_update_bits(priv->regmap, SEC_PULSE_GEN,
> +				  SEL_SEC_PULSE, 0);
> +}

It's redundant to check these regmap access, since the regmap is backed
by MMIO, and there's no reason it could fail.

Regards,
Yao Zi