linux-kernel - Re: [PATCH] hwmon: (pmbus/mp2975) Fix PGOOD in READ_STATUS

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Date:   Fri, 28 Jul 2023 07:26:02 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     Naresh Solanki <naresh.solanki@...ements.com>
Cc:     Jean Delvare <jdelvare@...e.com>,
        krzysztof.kozlowski+dt@...aro.org, linux-hwmon@...r.kernel.org,
        Patrick Rudolph <patrick.rudolph@...ements.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] hwmon: (pmbus/mp2975) Fix PGOOD in READ_STATUS_WORD

On 7/28/23 04:28, Naresh Solanki wrote:
> Hi Guenter,
> 
> 
> On Fri, 28 Jul 2023 at 15:30, Guenter Roeck <linux@...ck-us.net> wrote:
>>
>> On 7/28/23 01:25, Naresh Solanki wrote:
>>> From: Patrick Rudolph <patrick.rudolph@...ements.com>
>>>
>>> MPS returns PGOOD instead of PB_STATUS_POWER_GOOD_N.
>>> Fix that in the read_word_data hook.
>>>
>> Datasheets are not public, so I can not verify, but the code below
>> only handles MP2973 and MP2971. What about MP2975 ?
> I dont have MP2975 to even verify. I'm not sure if its applicable.
>>
>> Either case, this appears to affect most Monolithic chips, but
>> not all of them. Please limit the statement to known to be affected
>> chips.
> Yes. With what we observed, this affects mp2973 & mp2971.
> Will update accordingly.

Please also add a comment that MP2975 is likely affected but can not be
confirmed due to lack of a datasheet.

Thanks,
Guenter

>>
>>> Signed-off-by: Patrick Rudolph <patrick.rudolph@...ements.com>
>>> Signed-off-by: Naresh Solanki <Naresh.Solanki@...ements.com>
>>> ---
>>>    drivers/hwmon/pmbus/mp2975.c | 4 ++++
>>>    1 file changed, 4 insertions(+)
>>>
>>> diff --git a/drivers/hwmon/pmbus/mp2975.c b/drivers/hwmon/pmbus/mp2975.c
>>> index 28f33f4618fa..410b6eae6d02 100644
>>> --- a/drivers/hwmon/pmbus/mp2975.c
>>> +++ b/drivers/hwmon/pmbus/mp2975.c
>>> @@ -297,6 +297,10 @@ static int mp2973_read_word_data(struct i2c_client *client, int page,
>>>        int ret;
>>>
>>>        switch (reg) {
>>> +     case PMBUS_STATUS_WORD:
>>> +             ret = pmbus_read_word_data(client, page, phase, reg);
>>
>>                  if (ret < 0)
>>                          return ret;
>>
>> Please add a comment explaining what is going on.
> Sure.
>>
>>> +             ret ^= PB_STATUS_POWER_GOOD_N;
>>> +             break;
>>>        case PMBUS_OT_FAULT_LIMIT:
>>>                ret = mp2975_read_word_helper(client, page, phase, reg,
>>>                                              GENMASK(7, 0));
>>>
>>> base-commit: a4bb1ce5b9e3ca403c04e20ebeae77fd6447cb11
>>