Re: [PATCH v2] hwmon: max34451: Work around lost page

[Guenter Roeck]

On 4/10/25 16:59, Torreno, Alexis Czezar wrote:
> > > [External]
> > >
> > > On Mon, Apr 07, 2025 at 06:10:06PM -0700, William A. Kennington III wrote:
> > > > When requesting new pages from the max34451 we sometimes see that
> > > > the firmware responds with stale or bad data to reads that happen
> > > > immediately after a page change. This is due to a lack of clock
> > > > stretching after page changing on the device side when it needs more
> > > > time to complete the operation.
> > > >
> > > > To remedy this, the manufacturer recommends we wait 50us until the
> > > > firmware should be ready with the new page.
> > > >
> > > > Signed-off-by: William A. Kennington III <william@xxxxxxxxxxxxxxx>
> > >
> > > Applied to hwmon-next.
> > >
> > > Alexis: Do you happen to know if the new revision of MAX34451 still
> > > has this problem ? Also, it would be nice to get some feedback if the
> > > patch covers all affected devices.
> >
> > I unfortunately am not aware of this. Let me see if can get an answer from the
> > engr of the part.
>
> To follow up, here's the exact response I got.
>
> - This is not an issue with the part. As the fix mentions, "the manufacturer
> recommends we wait 50us until the firmware should be ready with the new page".
> Compliant with I2C/SMBus spec, some parts require a longer idle time for the
> bus to be free before receiving the next command, in this situation it is normal to
> recommend a longer idle time in between commands. It's more related to the
> part's inner timing and architecture.
>
> So I guess no specific changes related to this was made for later versions so the
> patch here should cover all.

Ok. Thanks a lot for looking into this!

Guenter