Re: Linux driver for IRPS5401 - status reg not found

[Michal Simek <michal.simek@xilinx.com>]

On 09. 04. 20 23:23, Guenter Roeck wrote:
> On 4/9/20 8:30 AM, Robert Hancock wrote:
>> On 2020-04-09 9:16 a.m., Guenter Roeck wrote:
>>> Hi Michal,
>>>
>>> On 4/9/20 7:29 AM, Michal Simek wrote:
>>> [ ... ]
>>>>
>>>> Just to let you know issue is with i2c driver. Here is my output for the
>>>> record.
>>>>
>>> Thanks a lot for the update.
>>>
>>>> irps5401-i2c-3-43
>>>> Adapter: i2c-0-mux (chan_id 2)
>>>> vin1:         11.56 V  (min =  +9.00 V, crit max = +14.00 V)
>>>> vin2:         11.56 V  (min =  +9.00 V, crit max = +14.00 V)
>>>> vin3:         11.56 V  (min =  +9.00 V, crit max = +14.00 V)
>>>> vin4:             N/A
>>>
>>> This is interesting; it means that the rail is not active (?) or
>>> not supported, or maybe even that the driver has a bug. The second
>>> chip reports a value here, so I guess the rail is inactive.
>>> If possible, it would be desirable to detect this during probe
>>> and not try to report values for this rail. It would be great if
>>> you can find the time to figure out what is going on.
>>
>> I would assume that either that rail is not used in that board design and was disabled in the non-volatile config on the chip, or alternately the chip allows combining outputs C and D (i.e. 3 and 4) into a single output in which case only one will report valid data. Not sure offhand if there is a way to detect those cases from the PMBus interface at probe time.
>>
> I think it may be the output disable register (0x38). One would have
> to know the i2c address, read the register, and set page bits
> accordingly. Overall, I am not sure if it is worth the trouble.
> Maybe we should just just add a note to the driver documentation.

https://www.xilinx.com/support/documentation/boards_and_kits/zcu104/ug1267-zcu104-eval-bd.pdf

page 83

0x43 is PHASE_C/D combined together a provide 1.2v.

Thanks,
Michal