Re: [PATCH 1/4] hwmon: (pmbus) Add get_error_flags support to regulator ops

[Guenter Roeck <linux@roeck-us.net>]

On 2/17/22 02:44, Zev Weiss wrote:
> The various PMBus status bits don't all map perfectly to the more
> limited set of REGULATOR_ERROR_* flags, but there's a reasonable
> number where they correspond well enough.
> 
> Signed-off-by: Zev Weiss <zev@bewilderbeest.net>
> ---
>   drivers/hwmon/pmbus/pmbus_core.c | 97 ++++++++++++++++++++++++++++++++
>   1 file changed, 97 insertions(+)
> 
> diff --git a/drivers/hwmon/pmbus/pmbus_core.c b/drivers/hwmon/pmbus/pmbus_core.c
> index 776ee2237be2..a274e8e524a5 100644
> --- a/drivers/hwmon/pmbus/pmbus_core.c
> +++ b/drivers/hwmon/pmbus/pmbus_core.c
> @@ -2417,10 +2417,107 @@ static int pmbus_regulator_disable(struct regulator_dev *rdev)
>   	return _pmbus_regulator_on_off(rdev, 0);
>   }
>   
> +/* A PMBus status flag and the corresponding REGULATOR_ERROR_* flag */
> +struct pmbus_regulator_status_assoc {
> +	int pflag, rflag;
> +};
> +
> +/* PMBus->regulator bit mappings for a PMBus status register */
> +struct pmbus_regulator_status_category {
> +	int func;
> +	int reg;
> +	const struct pmbus_regulator_status_assoc *bits; /* zero-terminated */
> +};
> +
> +static const struct pmbus_regulator_status_category pmbus_regulator_flag_map[] = {
> +	{
> +		.func = PMBUS_HAVE_STATUS_VOUT,
> +		.reg = PMBUS_STATUS_VOUT,
> +		.bits = (const struct pmbus_regulator_status_assoc[]) {
> +			{ PB_VOLTAGE_UV_WARNING, REGULATOR_ERROR_UNDER_VOLTAGE_WARN },
> +			{ PB_VOLTAGE_UV_FAULT,   REGULATOR_ERROR_UNDER_VOLTAGE },
> +			{ PB_VOLTAGE_OV_WARNING, REGULATOR_ERROR_OVER_VOLTAGE_WARN },
> +			{ PB_VOLTAGE_OV_FAULT,   REGULATOR_ERROR_REGULATION_OUT },
> +			{ },
> +		},
> +	}, {
> +		.func = PMBUS_HAVE_STATUS_IOUT,
> +		.reg = PMBUS_STATUS_IOUT,
> +		.bits = (const struct pmbus_regulator_status_assoc[]) {
> +			{ PB_IOUT_OC_WARNING,    REGULATOR_ERROR_OVER_CURRENT_WARN },
> +			{ PB_IOUT_OC_FAULT,      REGULATOR_ERROR_OVER_CURRENT },
> +			{ PB_IOUT_OC_LV_FAULT,   REGULATOR_ERROR_OVER_CURRENT },
> +			{ },
> +		},
> +	}, {
> +		.func = PMBUS_HAVE_STATUS_TEMP,
> +		.reg = PMBUS_STATUS_TEMPERATURE,
> +		.bits = (const struct pmbus_regulator_status_assoc[]) {
> +			{ PB_TEMP_OT_WARNING,    REGULATOR_ERROR_OVER_TEMP_WARN },
> +			{ PB_TEMP_OT_FAULT,      REGULATOR_ERROR_OVER_TEMP },
> +			{ },
> +		},
> +	},
> +};
> +
> +static int pmbus_regulator_get_error_flags(struct regulator_dev *rdev, unsigned int *flags)
> +{
> +	int i, status, statusreg;
> +	const struct pmbus_regulator_status_category *cat;
> +	const struct pmbus_regulator_status_assoc *bit;
> +	struct device *dev = rdev_get_dev(rdev);
> +	struct i2c_client *client = to_i2c_client(dev->parent);
> +	struct pmbus_data *data = i2c_get_clientdata(client);
> +	u8 page = rdev_get_id(rdev);
> +	int func = data->info->func[page];
> +
> +	*flags = 0;
> +
> +	for (i = 0; i < ARRAY_SIZE(pmbus_regulator_flag_map); i++) {
> +		cat = &pmbus_regulator_flag_map[i];
> +		if (!(func & cat->func))
> +			continue;
> +
> +		status = pmbus_read_byte_data(client, page, cat->reg);
> +		if (status < 0)
> +			return status;
> +
> +		for (bit = cat->bits; bit->pflag; bit++) {
> +			if (status & bit->pflag)
> +				*flags |= bit->rflag;
> +		}
> +	}
> +
> +	/*
> +	 * Map what bits of STATUS_{WORD,BYTE} we can to REGULATOR_ERROR_*
> +	 * bits.  Some of the other bits are tempting (especially for cases
> +	 * where we don't have the relevant PMBUS_HAVE_STATUS_*
> +	 * functionality), but there's an unfortunate ambiguity in that
> +	 * they're defined as indicating a fault *or* a warning, so we can't
> +	 * easily determine whether to report REGULATOR_ERROR_<foo> or
> +	 * REGULATOR_ERROR_<foo>_WARN.
> +	 */
> +	statusreg = data->has_status_word ? PMBUS_STATUS_WORD : PMBUS_STATUS_BYTE;
> +	status = pmbus_get_status(client, page, statusreg);
> +

pmbus_get_status() calls data->read_status if PMBUS_STATUS_WORD is provided
as parameter, and data->read_status is set to pmbus_read_status_byte()
if reading the word status is not supported. Given that, why not just call
pmbus_get_status(client, page, PMBUS_STATUS_WORD) ?

> +	if (status < 0)
> +		return status;
> +
> +	if (pmbus_regulator_is_enabled(rdev) && (status & PB_STATUS_OFF))
> +		*flags |= REGULATOR_ERROR_FAIL;
> +	if (status & PB_STATUS_IOUT_OC)
> +		*flags |= REGULATOR_ERROR_OVER_CURRENT;

If the current status register is supported, this effectively means that
an overcurrent warning is always reported as both REGULATOR_ERROR_OVER_CURRENT
and REGULATOR_ERROR_OVER_CURRENT_WARN. Is that intentional ?


> +	if (status & PB_STATUS_VOUT_OV)
> +		*flags |= REGULATOR_ERROR_REGULATION_OUT;

Same for voltage. On the other side, temperature limit violations are not
reported at all unless the temperature status register exists.
That seems to be a bit inconsistent to me.

> +
> +	return 0;
> +}
> +
>   const struct regulator_ops pmbus_regulator_ops = {
>   	.enable = pmbus_regulator_enable,
>   	.disable = pmbus_regulator_disable,
>   	.is_enabled = pmbus_regulator_is_enabled,
> +	.get_error_flags = pmbus_regulator_get_error_flags,
>   };
>   EXPORT_SYMBOL_NS_GPL(pmbus_regulator_ops, PMBUS);
>