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

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Date:   Tue, 21 Apr 2020 11:02:20 -0700
From:   Tony Lindgren <tony@...mide.com>
To:     Andreas Kemnade <andreas@...nade.info>
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

* Andreas Kemnade <andreas@...nade.info> [200421 06:54]:
> On Mon, 20 Apr 2020 23:11:18 +0200
> "H. Nikolaus Schaller" <hns@...delico.com> wrote:
> > The only maybe important observation was when I disabled all
> > kernel modules except *hdq*.ko and *bq27*.ko. Then I did only
> > get an emergency shell so that it is quite similar to the
> > scenario Andreas has tested. With this setup it did work.
> > 
> So I guess without idling uarts?
> 
> > I then tried to reenable other kernel modules but the result
> > wasn't convincing that it gives a reliable result.
> > 
> > So I have still no clear indication when the problem occurs and
> > when not.
> > 
> Hmm, last summer I had problems even without that patch reading
> temperature while doing umts transfers. Maybe there are some
> connections,
> maybe not. For that scenario we might have emc issues, thermal problems
> or a real kernel problem.

I have confimed here that logicpd torpedo devkit with battery
works just fine while entering off mode during idle. I can see
the temperature just fine with:

# cat /sys/class/power_supply/bq27000-battery/uevent
POWER_SUPPLY_NAME=bq27000-battery
POWER_SUPPLY_STATUS=Charging
POWER_SUPPLY_PRESENT=1
POWER_SUPPLY_VOLTAGE_NOW=3829000
POWER_SUPPLY_CURRENT_NOW=-592084
POWER_SUPPLY_CAPACITY_LEVEL=Normal
POWER_SUPPLY_TEMP=306
POWER_SUPPLY_TECHNOLOGY=Li-ion
POWER_SUPPLY_CHARGE_FULL_DESIGN=2056320
POWER_SUPPLY_CYCLE_COUNT=0
POWER_SUPPLY_POWER_AVG=0
POWER_SUPPLY_MANUFACTURER=Texas Instruments

This is 37xx though, maybe you have 35xx and there's some errata
that we're not handling?

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?

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.

Regards,

Tony

[0] https://www.ti.com/pdfs/wtbu/SWPZ009A_OMAP4430_Errata_Public_vA.pdf