Re: [PATCH v3 1/2] hwmon: (pmbus) Add Delta AHE-50DC fan control module driver

[Guenter Roeck]

On 12/7/21 4:41 PM, Zev Weiss wrote:
> On Tue, Dec 07, 2021 at 03:15:18PM PST, Guenter Roeck wrote:
> > On 12/7/21 1:53 PM, Zev Weiss wrote:
> > > On Tue, Dec 07, 2021 at 11:44:01AM PST, Guenter Roeck wrote:
> > > > On 12/7/21 11:22 AM, Zev Weiss wrote:
> > > > > On Tue, Dec 07, 2021 at 09:50:15AM PST, Guenter Roeck wrote:
> > > > > > On Mon, Dec 06, 2021 at 11:15:20PM -0800, Zev Weiss wrote:
> > > > > > > This device is an integrated module of the Delta AHE-50DC Open19 power
> > > > > > > shelf.  For lack of proper documentation, this driver has been developed
> > > > > > > referencing an existing (GPL) driver that was included in a code release
> > > > > > > from LinkedIn [1].  It provides four fan speeds, four temperatures, and
> > > > > > > one voltage reading, as well as a handful of warning and fault
> > > > > > > indicators.
> > > > > > >
> > > > > > > [1] https://github.com/linkedin/o19-bmc-firmware/blob/master/meta-openbmc/meta-linkedin/meta-deltapower/recipes-kernel/fancontrol-mod/files/fancontrol.c
> > > > > >
> > > > > > Hmm, that reference isn't really accurate anymore. I think it would be
> > > > > > better to just say that the device was found to be PMBus compliant.
> > > > >
> > > > > Sure, will do.
> > > >
> > > > Makes me wonder: How do you know that the referenced driver is for Delta AHE-50DC ?
> > >
> > > We'd been waiting for the source code for the software it ships with for a while, and were finally provided with that repo; everything I've observed from the factory software is consistent with the code in that driver.  A sampling:
> >
> > I assume you mean "Delta AHE-50DC" when you refer to "it".
>
> Yes.
>
> > [ ... ]
> > > > Can you check this with real hardware, by any chance ?
> > >
> > > If you mean running that code on it, yes -- here's the userspace utility that invokes that library routine:
> > >
> > >     root@bmc-oob:~# fan-util.sh
> > >     fan1 speed: 7860 RPM
> > >     fan2 speed: 7860 RPM
> > >     fan3 speed: 7620 RPM
> > >     fan4 speed: 7560 RPM
> > >     temperature1: 29.20 C
> > >     temperature2: 27.80 C
> > >     temperature3: 28.50 C
> > >     temperature4: 30.20 C
> > >     vin_undervolt_fault: no
> > >     overtemperature_warning: no
> > >     fan_fault: no
> > >     fan_warning: no
> > >     fan_status: ok
> >
> > That doesn't really tell me anything in the context of the driver you submitted.
> > Would it be possible to install your driver and provide the output from the
> > "sensors" command ? It should match the information from the proprietary
> > driver/tool.
>
> Thanks, in doing so I realized I'd neglected to prevent reads from unsupported registers in the read_word_data function, which was leading to the driver producing sysfs files for meaningless sensor limits that the device doesn't actually support.  With that fix (which I'll include in v4):

What a surprise. See drivers/hwmon/pmbus/dps920ab.c; that seems to be
a common theme for devices from Delta. I would suggest to add a similar
comment.

Guenter