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

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Date:   Tue, 21 Apr 2020 20:24:59 +0200
From:   Andreas Kemnade <andreas@...nade.info>
To:     Tony Lindgren <tony@...mide.com>
Cc:     "H. Nikolaus Schaller" <hns@...delico.com>,
        Evgeniy Polyakov <zbr@...emap.net>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-omap <linux-omap@...r.kernel.org>,
        Adam Ford <aford173@...il.com>,
        "Andrew F . Davis" <afd@...com>, Vignesh R <vigneshr@...com>
Subject: Re: [PATCHv3] w1: omap-hdq: Simplify driver with PM runtime
 autosuspend

On Tue, 21 Apr 2020 11:20:17 -0700
Tony Lindgren <tony@...mide.com> wrote:

> * H. Nikolaus Schaller <hns@...delico.com> [200421 18:14]:
> > > Am 21.04.2020 um 20:02 schrieb Tony Lindgren <tony@...mide.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.
>

hmm, he is testing without idling uarts, so I am a bit confused here,
the problem only seems to occur when more things are *active*.
Is something not handled in time.

Regards,
Andreas