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

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Date:   Tue, 21 Apr 2020 20:13:39 +0200
From:   "H. Nikolaus Schaller" <hns@...delico.com>
To:     Tony Lindgren <tony@...mide.com>
Cc:     Andreas Kemnade <andreas@...nade.info>,
        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

Hi Tony,

> Am 21.04.2020 um 20:02 schrieb Tony Lindgren <tony@...mide.com>:
> 
> * 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?

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.

> 
> 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.

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.

> 
> Regards,
> 
> Tony
> 
> [0] https://www.ti.com/pdfs/wtbu/SWPZ009A_OMAP4430_Errata_Public_vA.pdf
> 

BR and thanks,
Nikolaus