linux-kernel - Re: [PATCH 0/4] power: supply: add charge_behaviour property (force-discharge, inhibit-charge)

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Message-ID: <16d33b74-1b04-8b9e-7799-4f4b3a89c004@gmx.net>
Date:   Wed, 17 Nov 2021 19:36:08 +0100
From:   Thomas Koch <linrunner@....net>
To:     Thomas Weißschuh <linux@...ssschuh.net>
Cc:     linux-pm@...r.kernel.org, Sebastian Reichel <sre@...nel.org>,
        ibm-acpi-devel@...ts.sourceforge.net,
        platform-driver-x86@...r.kernel.org,
        Mark Gross <markgross@...nel.org>,
        Hans de Goede <hdegoede@...hat.com>,
        Henrique de Moraes Holschuh <hmh@....eng.br>,
        linux-kernel@...r.kernel.org, bberg@...hat.com, hadess@...ess.net,
        markpearson@...ovo.com, nicolopiazzalunga@...il.com,
        njoshi1@...ovo.com, smclt30p@...il.com
Subject: Re: [PATCH 0/4] power: supply: add charge_behaviour property
 (force-discharge, inhibit-charge)

Hi Thomas,

On 17.11.21 18:57, Thomas Weißschuh wrote:
> On 2021-11-16 17:56+0100, Thomas Koch wrote:
>> thank you very much for working on this. It is high time that we leave
>> external kernel modules for ThinkPads behind us.
>>
>> On 13.11.21 11:42, Thomas Weißschuh wrote:
>>> Hi,
>>>
>>> this series adds support for the charge_behaviour property to the power
>>> subsystem and thinkpad_acpi driver.
>>>
>>> As thinkpad_acpi has to use the 'struct power_supply' created by the generic
>>> ACPI driver it has to rely on custom sysfs attributes instead of proper
>>> power_supply properties to implement this property.
>>>
>>> Patch 1: Adds the power_supply documentation and basic public API
>>> Patch 2: Adds helpers to power_supply core to help drivers implement the
>>>     charge_behaviour attribute
>>> Patch 3: Adds support for force-discharge to thinkpad_acpi.
>>> Patch 4: Adds support for inhibit-discharge to thinkpad_acpi.
>>>
>>> Patch 3 and 4 are largely taken from other patches and adapted to the new API.
>>> (Links are in the patch trailer)
>>>
>>> Ognjen Galic, Nicolo' Piazzalunga, Thomas Koch:
>>>
>>> Your S-o-b is on the original inhibit_charge and force_discharge patches.
>>> I would like to add you as Co-developed-by but to do that it will also require
>>> your S-o-b. Could you give your sign-offs for the new patches, so you can be
>>> properly attributed?
>> S-o-b/Co-developed-by/Tested-by is fine with me.
>>
>> I tested your patches.
>>
>> Hardware:
>>
>> - ThinkPad X220, BAT0
>> - ThinkPad T450s, BAT0+BAT1
>> - ThinkPad X1C6, BAT0
>>
>> Test Results:
>>
>> 1. force-discharge
>>
>> Everythings works as expected
>> - Writing including disengaging w/ "auto" : OK
>> - Reading: OK
>>
>> - Battery discharging: OK
>> - Disengaging with "auto": OK
>>
>> 2. inhibit-charge
>>
>> Works as expected:
>> - Writing: OK
>>
>> - Disengaging with "auto": OK
>>
>>
>> Discrepancies:
>> - Battery charge inhibited: BAT0 OK, BAT1 no effect e.g. continues charging
>> - Reading: always returns "auto"
>
> I tested it on a T460s with two batteries and there inhibit-charge works
> fine for both batteries.
> What does not work is setting force-discharge for both batteries at the same
> time.
> This makes somewhat sense as on a physical level probably only one of them can
> be used at a time.

My experience confirms your consideration. The ThinkPad battery circuit
can handle exactly one battery at a time i.e.
- Charging, AC connected
- Forced discharging,  AC connected
- Discharging, AC disconnected
The other battery is always idle during this time.

> Mark Pearson: Could you confirm that this is the intended behaviour?
>
> In my changes queued for v2 of the series[0] I added validation of the written
> settings and an EIO is now reported if the settings were not applied, so this
> should help userspace handle this situatoin.
>
> The plan is to submit v2 after the first round of review for the core PM
> changes.

Please wait until i'm finished with testing your queued v2. I am getting
errors here and would first like to rule out homemade problems with my
kernel build and/or base version.

> [0] https://git.sr.ht/~t-8ch/linux/tree/charge-control


--
Freundliche Grüße / Kind regards,
Thomas Koch

Mail : linrunner@....net
Web  : https://linrunner.de/tlp