Re: [PATCH v2 3/3] rtc: ds1307: Add driver for Epson RX8901CE

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [High] Trickle charging is not explicitly disabled when requested, posing a battery safety hazard.
--

commit 1b11fec487efda4e55a4152eb696205b964ae2cd
Author: Fredrik M Olsson <fredrik.m.olsson@axis.com>

rtc: ds1307: Add driver for Epson RX8901CE

This commit adds I2C RTC driver support for the Epson RX8901CE. It includes
support for time reading/writing, Backup Switch Mode (BSM) configuration,
trickle charging, and battery voltage low status detection.

> diff --git a/drivers/rtc/rtc-ds1307.c b/drivers/rtc/rtc-ds1307.c
> index bf42c250ea7d1..23dd104aa2be7 100644
> --- a/drivers/rtc/rtc-ds1307.c
> +++ b/drivers/rtc/rtc-ds1307.c

[ ... ]

> @@ -568,6 +717,26 @@ static u8 do_trickle_setup_rx8130(struct ds1307 *ds1307, u32 ohms, bool diode)
>  	return setup;
>  }
>  
> +static int do_trickle_setup_rx8901(struct ds1307 *ds1307, u32 ohms __always_unused, bool diode)
> +{
> +	int ret;
> +	unsigned int setup;
> +
> +	ret = regmap_read(ds1307->regmap, RX8901_REG_PWSW_CFG, &setup);
> +	if (ret) {
> +		dev_err(ds1307->dev, "Failed to read PWSW_CFG register\n");
> +		return ret;
> +	}
> +
> +	/* Enable low battery voltage detection */
> +	setup |= RX8901_REG_PWSW_CFG_VBATLDETEN;
> +
> +	if (diode)
> +		setup |= RX8901_REG_PWSW_CFG_CHGEN;

[Severity: High]
If diode is false, does this code need to explicitly clear the
RX8901_REG_PWSW_CFG_CHGEN bit?

Because RX8901_REG_PWSW_CFG is a battery-backed register, a previously
set charge enable bit (for example, from a bootloader or a prior warm
reboot) might remain set even if trickle charging is explicitly disabled
by the system configuration.

Could this lead to a physical safety hazard by unintentionally charging a
primary (non-rechargeable) battery if the bit is not explicitly cleared
using something like setup &= ~RX8901_REG_PWSW_CFG_CHGEN?

> +
> +	return setup;
> +}

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260520-ds1307-rx8901-add-v2-0-e069ea32e1db@axis.com?part=3