[PATCH linux dev-5.8 0/3] MAX31785 Fan Controller Work-arounds

[Joel Stanley]

On Thu, 27 Aug 2020 at 13:30, Andrew Jeffery <andrew at aj.id.au> wrote:
>
> Hello,
>
> This series works around reliability problems with the MAX31785 fan controller
> as observed in the field on some POWER systems.
>
> I'm the first to admit the patches are not elegant, so feedback there is
> appreciated.

The way you implemented the loop took me several goes to grok. I
finally got there.


>
> Separately, our previous workarounds have run aground upstream as the hwmon
> maintainer was unable to reproduce our observations on the MAX31785 evaluation
> kit. I've recently received an evaluation kit, so I plan on putting some of
> these issues to the test myself. Ultimately this will help determine whether we
> have issues with our fan card designs or whether the controller itself is at
> fault (I have to admit, given some of the failures, it's hard to see how the
> controller might not be at fault). Basically, this paragraph is my excuse for
> not pushing these patches further upstream for the moment; I will re-evaluate
> once I have the results from testing against the evkit.

I would post this series upstream so Guneter has some context for
future patches that come out of your investigation.

>
> In the mean time, these patches resolve issues we've seen in some system
> deployments. Taken together, I've put the driver through an unbind/bind loop
> of over 20,000 iterations with no "loss" of fans, where prior to the series we
> typically achieved only a few hundred. This feels like a significant
> improvement, so please consider merging despite their ugliness.

Do you want these in dev-5.4, or both 5.4 and 5.8?

>
> Cheers,
>
> Andrew
>
> Andrew Jeffery (3):
>   pmbus: (max31785) Retry enabling fans after writing MFR_FAN_CONFIG
>   pmbus: (max31785) Add a local pmbus_set_page() implementation
>   pmbus: (core) Add a one-shot retry in pmbus_set_page()
>
>  drivers/hwmon/pmbus/max31785.c   | 55 ++++++++++++++++++++++++++------
>  drivers/hwmon/pmbus/pmbus_core.c | 33 ++++++++++++-------
>  2 files changed, 66 insertions(+), 22 deletions(-)
>
> --
> 2.25.1
>