Re: [PATCHv3] w1: omap-hdq: Simplify driver with PM runtime autosuspend

Tony Lindgren
2020-04-21T18:20:24Z

* H. Nikolaus Schaller <hns@goldelico.com> [200421 18:14]:
> > Am 21.04.2020 um 20:02 schrieb Tony Lindgren <tony@atomide.com>:
> > This is 37xx though, maybe you have 35xx and there's some errata
> > that we're not handling?
>
> No, it is dm3730 on three different units I have tried.
>
> > I'm only seeing "2.7. HDQTM/1-Wire® Communication Constraints"
> > for external pull-up resitor in 34xx errata at [0].
> >
> > I wonder if wrong external pull could cause flakyeness after
> > enabling the hdq module?
>
> I have checked and we have 10 kOhm pullup to 1.8 V and a 470 Ohm
> series resistor.

OK

> > If nothing else helps, you could try to block idle for hdq
> > module, but I have a feeling that's a workaround for something
> > else.
>
> Well, what helps is reverting the patch and using the old driver
> (which did work for several years). So I would not assume that
> there is a hardware influence. It seems to be something the new
> driver is doing differently.

Well earlier hdq1w.c did not idle, now it does. If you just want
to keep it enabled like earlier, you can just add something like:

&hdqw1w {
ti,no-idle;
};

> I need more time to understand and trace this issue on what it
> depends... It may depend on the sequence some other modules are
> loaded and what the user-space (udevd) is doing in the meantime.

Yes would be good to understand what goes wrong here before we
apply the ti,no-idle as that will block SoC deeper idle states.

Regards,

Tony