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

[Richard Fitzgerald]

On 15/10/2020 11:25, Nicolas Saenz Julienne wrote:
> 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.
Info on the codecs is available from www.cirrus.com.
The Lochnagar audio development board is not a hat, but it can be wired
over to the RPi GPIO header. It is not specific to the RPi.

> 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).
Ok, will change.

> > 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@xxxxxxxxxxxxxxxxxxxxx>
> > ---
>
> 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

We want something in mainline so that it can be used by people
developing on mainline and taken as a starting point for configuring
the codecs for other host platforms. The RPi is a convenient platform to
use as the base because it is widely available and low-cost.

> 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