linux-kernel - Re: [PATCH 6/7] ARM: dts: Add dts for Raspberry Pi 4 + Cirrus Logic Lochnagar2

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Date:   Thu, 15 Oct 2020 12:25:49 +0200
From:   Nicolas Saenz Julienne <nsaenzjulienne@...e.de>
To:     Richard Fitzgerald <rf@...nsource.cirrus.com>, broonie@...nel.org,
        robh+dt@...nel.org
Cc:     patches@...nsource.cirrus.com, alsa-devel@...a-project.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-rpi-kernel@...ts.infradead.org
Subject: Re: [PATCH 6/7] ARM: dts: Add dts for Raspberry Pi 4 + Cirrus Logic
 Lochnagar2

Hi Richard,
your series is very welcome, upstream support for audio codecs on the RPi4 has
always been lackluster.

Could you provide more information on the actual products? Are there custom
made hats for the RPi4 or this wired into a generic development board.

On Wed, 2020-10-14 at 15:54 +0100, Richard Fitzgerald wrote:
> This is based on the default bcm2711-rpi-4-b.dts.

Note that you could've included bcm2711-rpi-4.dts (as if it was a .dtsi).

> Configurations are provided for Cirrus Logic codecs CS42L92, CS47L15,
> CS47L24, CS47L35, CS47L90 and WM8998.
> 
> For each codec there is a sound node and a codec device node and both
> default to disabled. Enable the pair for the codec in use.
> 
> Signed-off-by: Richard Fitzgerald <rf@...nsource.cirrus.com>
> ---

Sadly I don't think creating a new device tree is a good solution here. If we
were to do so for every RPi hat/usage it'd become unmanageable very fast. There
is a way to maintain this in the open nonetheless. I suggest you build a DT
overlay and submit it to https://github.com/raspberrypi/linux, see
'arch/arm/boot/dts/overlays.' The Raspberry Pi engineers have a kernel branch
that tracks of the latest kernel release, so once you get the rest of patches
sorted out and they are included in a release it'll make sense to do so.

I can't tell for other distros, but opensuse packages overlays, so the effort
will ultimately be useful to users.

Regards,
Nicolas

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