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([2600:1700:e321:62f0:329c:23ff:fee3:9d7c]) by smtp.gmail.com with ESMTPSA id h4sm4526118qkf.66.2022.02.17.16.02.59 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 17 Feb 2022 16:03:00 -0800 (PST) Sender: Guenter Roeck Message-ID: <3bfa7f1f-ef5d-b222-894b-b15a2270996d@roeck-us.net> Date: Thu, 17 Feb 2022 16:02:58 -0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.5.0 Content-Language: en-US To: Zev Weiss Cc: Jean Delvare , linux-hwmon@vger.kernel.org, openbmc@lists.ozlabs.org, Greg Kroah-Hartman , linux-kernel@vger.kernel.org, Mark Brown , Liam Girdwood References: <20220217104444.7695-1-zev@bewilderbeest.net> <20220217104444.7695-2-zev@bewilderbeest.net> From: Guenter Roeck Subject: Re: [PATCH 1/4] hwmon: (pmbus) Add get_error_flags support to regulator ops In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 >>> --- >>>  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_ or >>> +     * REGULATOR_ERROR__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