Re: [PATCH v2 4/4] regulator: fan53555: Add support for mode operations on Silergy devices

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:

Pre-existing issues:
- [High] fan53555_set_mode() incorrectly updates the voltage register instead of the mode register when setting REGULATOR_MODE_NORMAL, causing severe voltage corruption on chips where these registers are distinct.
--

--- Patch [4]: [PATCH v2 4/4] regulator: fan53555: Add support for mode operations on Silergy devices ---
commit 4b739645e4ed09b01a00b9bb826b1cf9a4da63a8
Author: Victor Krawiec <victor.krawiec@arturia.com>

regulator: fan53555: Add support for mode operations on Silergy devices

This commit makes the PWM mode configurable from devicetree for Silergy
devices. It adds a mapping function for devicetree mode flags to regulator
modes, allowing boards to force PWM mode to manage supply ripple.

> diff --git a/drivers/regulator/fan53555.c b/drivers/regulator/fan53555.c
> index c282236959b18..85f46874eb49d 100644
> --- a/drivers/regulator/fan53555.c
> +++ b/drivers/regulator/fan53555.c

[ ... ]

> @@ -389,6 +390,18 @@ static int rk8602_voltages_setup_rockchip(struct fan53555_device_info *di)
>  	return 0;
>  }
>  
> +static inline unsigned int fan53555_map_mode(unsigned int mode)
> +{
> +	switch (mode) {
> +	case FAN53555_REGULATOR_MODE_FORCE_PWM:
> +		return REGULATOR_MODE_FAST;
> +	case FAN53555_REGULATOR_MODE_AUTO:
> +		return REGULATOR_MODE_NORMAL;

[Severity: High]
This isn't a bug introduced by this patch, but mapping to REGULATOR_MODE_NORMAL
exposes a pre-existing issue in fan53555_set_mode().

When REGULATOR_MODE_NORMAL is selected, fan53555_set_mode() updates di->vol_reg
instead of di->mode_reg:

fan53555_set_mode() {
	...
	case REGULATOR_MODE_NORMAL:
		regmap_update_bits(rdev->regmap, di->vol_reg, di->mode_mask, 0);
		break;
	...
}

On chips where the mode register and voltage register are distinct (such as
RK8602, FAN53526, or TCS), clearing di->mode_mask inside di->vol_reg corrupts
the voltage selection bits. This can cause a sudden, unintended drop in output
voltage leading to a system lockup.

Is it possible to correct the register used in fan53555_set_mode() before
enabling this mode mapping?

> +	default:
> +		return REGULATOR_MODE_INVALID;
> +	}
> +}

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260720100336.62004-1-victor.krawiec@arturia.com?part=4