RE: [PATCH v9 1/2] ASoC: dt-bindings: realtek,rt5575: add support for ALC5575

[Oder Chiou <oder_chiou@realtek.com>]

> -----Original Message-----
> From: Rob Herring <robh@kernel.org>
> Sent: Thursday, December 11, 2025 11:39 PM
> To: Oder Chiou <oder_chiou@realtek.com>
> Cc: cezary.rojewski@intel.com; broonie@kernel.org; lgirdwood@gmail.com;
> krzk+dt@kernel.org; conor+dt@kernel.org; perex@perex.cz;
> linux-sound@vger.kernel.org; devicetree@vger.kernel.org;
> alsa-devel@alsa-project.org; Flove(HsinFu) <flove@realtek.com>; Shuming [范
> 書銘] <shumingf@realtek.com>; Jack Yu <jack.yu@realtek.com>; Derek [方德
> 義] <derek.fang@realtek.com>
> Subject: Re: [PATCH v9 1/2] ASoC: dt-bindings: realtek,rt5575: add support for
> ALC5575
> 
> 
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> 
> 
> On Thu, Dec 11, 2025 at 07:01:29PM +0800, Oder Chiou wrote:
> > Audio codec with I2S, I2C and SPI.
> >
> > Signed-off-by: Oder Chiou <oder_chiou@realtek.com>
> > ---
> >  .../bindings/sound/realtek,rt5575.yaml        | 44
> +++++++++++++++++++
> >  1 file changed, 44 insertions(+)
> >  create mode 100644
> Documentation/devicetree/bindings/sound/realtek,rt5575.yaml
> >
> > diff --git a/Documentation/devicetree/bindings/sound/realtek,rt5575.yaml
> b/Documentation/devicetree/bindings/sound/realtek,rt5575.yaml
> > new file mode 100644
> > index 000000000000..60f9af399dd2
> > --- /dev/null
> > +++ b/Documentation/devicetree/bindings/sound/realtek,rt5575.yaml
> > @@ -0,0 +1,44 @@
> > +# SPDX-License-Identifier: GPL-2.0-only OR BSD-2-Clause
> > +%YAML 1.2
> > +---
> > +$id: http://devicetree.org/schemas/sound/realtek,rt5575.yaml#
> > +$schema: http://devicetree.org/meta-schemas/core.yaml#
> > +
> > +title: ALC5575 audio CODEC
> > +
> > +maintainers:
> > +  - Oder Chiou <oder_chiou@realtek.com>
> > +
> > +description:
> > +  The device supports both I2C and SPI. I2C is mandatory, while SPI is
> > +  optional depending on the hardware configuration.
> > +
> > +allOf:
> > +  - $ref: /schemas/spi/spi-peripheral-props.yaml#
> > +  - $ref: dai-common.yaml#
> > +
> > +properties:
> > +  compatible:
> > +    enum:
> > +      - realtek,rt5575
> > +      - realtek,rt5575-use-spi
> > +
> > +  reg:
> > +    maxItems: 1
> > +
> > +required:
> > +  - compatible
> > +  - reg
> > +
> > +unevaluatedProperties: false
> > +
> > +examples:
> > +  - |
> > +    i2c {
> > +        #address-cells = <1>;
> > +        #size-cells = <0>;
> > +        codec@57 {
> > +            compatible = "realtek,rt5575";
> > +            reg = <0x57>;
> > +        };
> > +    };
> 
> It is completely unclear what you are doing in the SPI case. I
> deciphered it studying the driver. I shouldn't have to do that, your
> binding should make that clear.
> 
> So your DT must look like this:
> 
> i2c {
>         codec@57 {
>                 compatible = "realtek,rt5575-use-spi";
>                 reg = <0x57>;
>         };
> };
> 
> spi {
>         codec@1 {
>                 compatible = "realtek,rt5575";
>                 reg = <0x1>;
>         };
> };
> 
> First, there's no need for "-use-spi" because you can just check if
> there is a rt5575 SPI device and use it if there is. Why would you have
> the SPI device and not use it?

The compatible realtek,rt5575-use-spi will be removed, and if there is no
SPI device in the DTS, the warning message will be shown as "The hardware
configuration should be with built-in flash".

> But really it is not ideal having 2 device nodes for a single device. It
> would be much simpler to just have something like this in the i2c node:
> 
> spi-parent = <&spi0 1>;
> 
> Where the cell is the chip-select #.
> 
> We have an 'i2c-parent' already for similar reasons when there are 2
> bus connections.

In the current kernel, I cannot find any function to obtain a
struct spi_controller when no SPI device is defined in the DTS. This was
possible in older kernels using the legacy spi_busnum_to_master(), but
that function is no longer available in upstream.

Thanks,
Oder