Messages in this thread | | | Date | Thu, 17 Feb 2022 16:02:58 -0800 | From | Guenter Roeck <> | Subject | Re: [PATCH 1/4] hwmon: (pmbus) Add get_error_flags support to regulator ops |
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On 2/17/22 15:37, Zev Weiss wrote: > On Thu, Feb 17, 2022 at 10:11:32AM PST, Guenter Roeck wrote: >> 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) ? > > Good point, I'll change it to do that instead. (And send v2 separately from the power-efuse driver patches.) > >> >>> + 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 ? >> > > No, but I don't think (by my reading of the spec) that's what would happen? > > I'm looking at table 16 ("STATUS_WORD Message Contents") in section 17.2 ("STATUS_WORD") of Part II of revision 1.3.1 of the PMBus spec, which says that bit 4 of the low byte (PB_STATUS_IOUT_OC) indicates an output overcurrent fault, not a warning (in contrast to most of the other bits, which may indicate either). > >> >>> + if (status & PB_STATUS_VOUT_OV) >>> + *flags |= REGULATOR_ERROR_REGULATION_OUT; >> >> Same for voltage. > > Likewise, PB_STATUS_VOUT_OV is specified as indicating a fault, not a warning. >
Ok, that makes sense.
>> 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. >> > > Right -- that's because PB_STATUS_TEMPERATURE is one of the "fault or warning" bits (unlike VOUT_OV and IOUT_OC), and hence it's an ambiguous case as described in the comment before the pmbus_get_status() call. > > It's certainly not ideal, but it seemed like the best approach I could see given the semantics of the available flags -- I'm open to other possibilities though if there's something else that would work better. >
My approach would be to report a warning if no temperature warning/fault is set from PMBUS_STATUS_TEMPERATURE but PB_STATUS_TEMPERATURE is set in the status register.
Something like
if (!(*flags & (REGULATOR_ERROR_OVER_TEMP | REGULATOR_ERROR_OVER_TEMP_WARN)) && (status & PB_STATUS_TEMPERATURE)) *flags |= REGULATOR_ERROR_OVER_TEMP_WARN;
While not perfect, it would be better than reporting nothing.
Guenter
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