linux-kernel - Re: [PATCH 1/3] dt-bindings: mfd: Add power-button option for TI TPS6594 PMIC

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Message-Id: <DBPFTXDNMIS5.1RCL30X7VN5MG@baylibre.com>
Date: Wed, 30 Jul 2025 15:52:33 +0200
From: "Markus Schneider-Pargmann" <msp@...libre.com>
To: "Michael Walle" <mwalle@...nel.org>, "Jon Cormier"
 <jcormier@...ticallink.com>, "Jerome Neanne" <jneanne@...libre.com>
Cc: "Job Sava" <jsava@...ticallink.com>, "Krzysztof Kozlowski"
 <krzk@...nel.org>, "Lee Jones" <lee@...nel.org>, "Rob Herring"
 <robh@...nel.org>, "Krzysztof Kozlowski" <krzk+dt@...nel.org>, "Conor
 Dooley" <conor+dt@...nel.org>, "Julien Panis" <jpanis@...libre.com>,
 "Dmitry Torokhov" <dmitry.torokhov@...il.com>,
 <devicetree@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
 <linux-input@...r.kernel.org>
Subject: Re: [PATCH 1/3] dt-bindings: mfd: Add power-button option for TI
 TPS6594 PMIC

Hi,

I think my mail wasn't sent properly, so here we go again:

On Mon Jul 21, 2025 at 8:42 AM CEST, Michael Walle wrote:
> [+ Jerome and Markus ]
>
> Hi,
>
>> > > > Someone knowing the device should come with arguments whether
>> > > > other states for this are useful at all. Or not useful and then argument
>> > > > that in commit msg for example.
>> > > The other states are not useful for the kernel. Only the push button
>> > > has a need for an interrupt handler. The other states the PMIC handles
>> > > on its own.
>> > >
>> > > What exactly do you want me to change?
>> >
>> > Because the driver isn't setting the configuration anyway, wouldn't
>> > it be possible to read the config bits (Register 0x3c, bits 7-6) to
>> > figure out whether the pin is configured as power-button instead of
>> > having this property?
>> >
>> > I mean, the correct config is likely stored in the NVM anyway, and
>> > reconfiguring it to another value seems unlikely.
>> Currently, the TPS MFD driver only loads the power button driver if
>> the flag is set.  We could put that discovery code in the MFD driver,
>> but what if the system designer doesn't want the power button driver?
>
> The device tree is not for configuration. The designer can just
> ignore the input event in that case.
>
>> I'm not sure auto detecting it makes sense.
>
> Why?
>
>> We are basing this on the other TI PMIC drivers and how they are
>> configured. I'm not sure I want to reinvent the wheel, so to speak.
>
> That was never a good reason. Maybe there was a reason for the
> TPS65219. Markus? Jerome? I haven't found anything in the commit
> messages or cover letters. Only that it is "optional". Not sure what
> that means. According to the TPS65219 datasheet, that pin if not
> used shall be configured as EN and be connected to VSYS.

I don't think the TPS65219 has a config register to detect if the pin is
a power-button that's why a devicetree description was necessary.
Looking at it now, it should probably have been an enum for TPS65219. It
is not relevant to any software but it is not describing the
configuration fully.

Best
Markus

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