Re: [PATCH v2 05/15] arm64: dts: freescale: imx8mn-var-som: Add support for WM8904 audio codec

[Frank Li <Frank.li@oss.nxp.com>]

On Tue, Jul 07, 2026 at 03:29:18PM +0200, Stefano Radaelli wrote:
> Hi Frank,
>
> On Mon, Jul 06, 2026 at 10:00:01AM -0500, Frank Li wrote:
> > On Mon, Jul 06, 2026 at 10:09:47AM +0000, sashiko-bot@kernel.org wrote:
> > > Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
> > > - [Medium] The `simple-audio-card,routing` property maps `Microphone Jack` to `IN1L` and `IN1R` but omits the connection to the `MICBIAS` supply, which will leave standard electret microphones unpowered.
> > > --
> > >
> > > commit 78e4da0f71f2e53ae4312cbe5ceecb0f6f2345db
> > > Author: Stefano Radaelli <stefano.r@variscite.com>
> > >
> > > arm64: dts: freescale: imx8mn-var-som: Add support for WM8904 audio codec
> > >
> > > This commit adds support for the WM8904 audio codec on the VAR-SOM-MX8MN board.
> > > It configures the device on the I2C bus, enables the SAI peripheral, and adds a
> > > simple-audio-card sound node to expose the sound card to the system.
> > >
> > > > diff --git a/arch/arm64/boot/dts/freescale/imx8mn-var-som.dtsi b/arch/arm64/boot/dts/freescale/imx8mn-var-som.dtsi
> > > > index 09146ab763858..e2e04ad2fbb65 100644
> > > > --- a/arch/arm64/boot/dts/freescale/imx8mn-var-som.dtsi
> > > > +++ b/arch/arm64/boot/dts/freescale/imx8mn-var-som.dtsi
> > >
> > > [ ... ]
> > >
> > > > @@ -42,6 +50,34 @@ reg_phy_vddio: regulator-phy-vddio {
> > > >  		regulator-min-microvolt = <1800000>;
> > > >  		regulator-max-microvolt = <1800000>;
> > > >  	};
> > > > +
> > > > +	sound {
> > > > +		compatible = "simple-audio-card";
> > > > +		simple-audio-card,bitclock-master = <&codec_dai>;
> > > > +		simple-audio-card,format = "i2s";
> > > > +		simple-audio-card,frame-master = <&codec_dai>;
> > > > +		simple-audio-card,mclk-fs = <256>;
> > > > +		simple-audio-card,name = "wm8904-audio";
> > > > +		simple-audio-card,routing =
> > > > +			"Headphone Jack", "HPOUTL",
> > > > +			"Headphone Jack", "HPOUTR",
> > > > +			"IN2L", "Line In Jack",
> > > > +			"IN2R", "Line In Jack",
> > > > +			"IN1L", "Microphone Jack",
> > > > +			"IN1R", "Microphone Jack";
> > > [Severity: Medium]
> > > Will standard electret microphones remain unpowered with this routing?
> > >
> > > The routing maps "Microphone Jack" to "IN1L" and "IN1R", but omits a link to
> > > the "MICBIAS" supply (e.g., "Microphone Jack", "MICBIAS"). Because "MICBIAS"
> > > is defined as a DAPM supply widget in the codec driver, DAPM will not enable
> > > it unless it has an explicit routing link connecting it to the active audio
> > > path. This could leave the microphone without its required bias voltage when
> > > recording.
> >
> > Is this true?
> >
> > Frank
> >
>
> Thanks for pointing this out.
>
> This audio routing is not new for this board. It follows the same WM8904
> routing that we have been using on our other platforms for quite some
> time, and we are not aware of any reported issues related to the
> analogue microphone path.
>
> If adding an explicit route to MICBIAS is indeed required by the
> codec driver, then this would not be specific to this board but would
> potentially apply to all of our WM8904-based platforms.
>
> I'd prefer not to introduce this functional change as part of this DTS
> alignment series without validating it across all affected platforms.
> If needed, we can investigate the MICBIAS routing separately and
> submit a dedicated fix covering all WM8904-based boards.

Okay, thanks.

Frank

>
> Thanks,
> Stefano