Re: [PATCH] hwmon: (pmbus/xdpe1a2g7b) Add regulator support

[sashiko-bot@kernel.org]

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

Pre-existing issues:
- [Critical] This problem wasn't introduced by this patch, but the PMBus core function `pmbus_data2reg_vid()` hardcodes the VR11 VID calculation formula and completely ignores the `vrm_version` parameter configured by the driver. When the `xdpe1a2g7b` driver operates in `nvidia195mv` VID mode, calls to `regulator_set_voltage()` will convert the target voltage to a completely incorrect VR11 VID code. For example, a request for 200mV is incorrectly clamped to 500mV and converted to a VR11 VID of 0xB2, which the hardware interprets in `nvidia195mv` mode as 1.08V. This applies unexpected and potentially destructive voltages to attached components.
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commit 970e2131ac4cd9e077822790586db122a481d9fb
Author: Abdurrahman Hussain <abdurrahman@nexthop.ai>

hwmon: (pmbus/xdpe1a2g7b) Add regulator support

Register both dual-loop output channels with the regulator framework by
populating regulator_desc[] and num_regulators in pmbus_driver_info.
This exposes the standard PMBus OPERATION-based on/off control and
status reporting to consumer drivers.

> diff --git a/drivers/hwmon/pmbus/xdpe1a2g7b.c b/drivers/hwmon/pmbus/xdpe1a2g7b.c
> index 971e7b73752ea..9455ef443b2b3 100644
> --- a/drivers/hwmon/pmbus/xdpe1a2g7b.c
> +++ b/drivers/hwmon/pmbus/xdpe1a2g7b.c
[ ... ]
> @@ -72,6 +79,10 @@ static struct pmbus_driver_info xdpe1a2g7b_info = {
>  	.func[1] = PMBUS_HAVE_VIN | PMBUS_HAVE_VOUT | PMBUS_HAVE_STATUS_VOUT |
>  		   PMBUS_HAVE_IIN | PMBUS_HAVE_IOUT | PMBUS_HAVE_STATUS_IOUT |
>  		   PMBUS_HAVE_PIN | PMBUS_HAVE_POUT | PMBUS_HAVE_STATUS_INPUT,
> +#if IS_ENABLED(CONFIG_SENSORS_XDPE1A2G7B_REGULATOR)
> +	.num_regulators = XDPE1A2G7B_PAGE_NUM,
> +	.reg_desc = xdpe1a2g7b_reg_desc,

[Severity: Critical]
This is a pre-existing issue, but does enabling regulator support here expose
attached hardware to destructive voltages when operating in nvidia195mv VID
mode?

The core PMBus framework translates microvolts into raw register encodings via
pmbus_data2reg_vid(), but it currently hardcodes the VR11 VID calculation
formula and completely ignores the vrm_version parameter configured by the
driver.

For example, if regulator_set_voltage() requests 200mV, the core does:

drivers/hwmon/pmbus/pmbus_core.c:pmbus_data2reg_vid() {
	val = clamp_val(val, 500, 1600);
	return 2 + DIV_ROUND_CLOSEST_ULL((1600LL - val) * 100LL, 625);
}

This incorrectly clamps the request to 500mV and converts it to a VR11 VID of
0xB2. The hardware interprets 0xB2 in nvidia195mv mode as 1.08V.

Writing these values into the PMBUS_VOUT_COMMAND register of an nvidia195mv
compliant device translates low-voltage requests into dangerously high physical
voltage output.

Could pmbus_data2reg_vid() be updated to branch on vrm_version before exposing
this regulator interface?

> +#endif
>  };

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260619-xdpe1a2g7b-v1-1-428c3847be0d@nexthop.ai?part=1