Re: [PATCH 0/7] hwmon: (max31790) Fixes and improvements

Guenter Roeck
2021-06-01T12:09:00Z

On Tue, Jun 01, 2021 at 10:29:48AM +0200, Václav Kubernát wrote:
> Hello,
>
[ short reply - I am on the road. I'll look into your replies in
more detail later ]

> I have tested your patches. It seems like the driver is now a lot more
> usable, thanks. What seems to be still unusable for me, is RPM mode.
> The chip creates an effort to set the RPM, but it almost never
> stabilizes. I think the reason is mainly because the driver doesn't
> work with registers like "window" and "pwm rate of change". PWM mode
> seems to work fine.
>
Agreed; I found the same problem. I actually tried to implement support
for an attribute to support the window registers, but could not find
working settings. I only played with window registers, though, so we'll
probably need attributes for both window mode and pwm rate of change.

> I think some of the patches in my patch series on the chip are now
> obsolete. However, I do think at least fanX_div should be implemented.
> When testing with Sunon PF36281BX-000U-S99 (its max RPM is 23000), the
> default divisor is not enough (one bit of change equals to about 500
> RPM). The only way to change the divisor right now, is to set the
> target RPM or min RPM.
>
Agreed.

> There is also the regmap patch, but I've implemented that one mainly
> because it made the driver a bit easier to debug.
>
Only reason for me to omit that was because it was buggy (FWIW, I didn't
know either that the defalt caching mode is "do not cache", and that all
the 'volatile' declarations were useless).

Guenter