linux-kernel - Re: [PATCH v2 1/2] arm64: dts: ti: k3-am65: disable optional peripherals by default

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Date:   Wed, 9 Mar 2022 11:11:52 +0200
From:   Tony Lindgren <tony@...mide.com>
To:     Matthias Schiffer <matthias.schiffer@...tq-group.com>
Cc:     Rob Herring <robh+dt@...nel.org>, Arnd Bergmann <arnd@...db.de>,
        Olof Johansson <olof@...om.net>, soc@...nel.org,
        Vignesh Raghavendra <vigneshr@...com>,
        Tero Kristo <kristo@...nel.org>, jan.kiszka@...mens.com,
        linux-arm-kernel@...ts.infradead.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, Nishanth Menon <nm@...com>
Subject: Re: [PATCH v2 1/2] arm64: dts: ti: k3-am65: disable optional
 peripherals by default

Hi,

* Matthias Schiffer <matthias.schiffer@...tq-group.com> [220228 10:29]:
> AFAICT, disabling non-operatational devices in the board DTS instead of
> the SoC DTSI is worse than the alternatives in every way:
> 
> - Verbose board DTS: You have to think about all the devices that exist
> in the SoC, not just the ones you want to use
> - Adding new nodes without `status = "disabled" to SoC DTSI can
> potentially cause issues on dependent boards
> - It doesn't solve the issues that not having `status = "disabled"` in
> the DTSI is supposed to solve

My preference is the least amount of tinkering in the dts files
naturally :) It really does not matter if the extra dts churn is to
enable or disable devices, it should not be needed at all.

To summarize, my main point really is the following:

There should not be any need to tag the SoC internal devices with anything
in the dts files. The device drivers should be able to just deal with the
situation. IMO devices should be tagged with disabled or reserved when
they are not accessible for example because of being used by secure mode
for example. If the the status needs to be set to anything, it really is
a symptom of incomplete handling somewhere.

Regards,

Tony