Re: [PATCH v5 07/13] ARM: dts: imx6ul: Add Variscite WM8904 and WM8731 support

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [High] sound: simple-audio-card: inverted DAPM routing for WM8731 microphone
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commit fed6a844cfc964e2cba2d176b3deac928acc5e54
Author: Stefano Radaelli <stefano.r@variscite.com>

ARM: dts: imx6ul: Add Variscite WM8904 and WM8731 support

Add shared WM8904 and WM8731 codec and sound-card descriptions for
VAR-SOM-6UL and DART-6UL. Reuse imx6ul-var-som-audio.dtsi for SAI2
and select the clock setup and audio routes in each codec file.

[ ... ]

> diff --git a/arch/arm/boot/dts/nxp/imx/imx6ul-imx6ull-var-wm8731.dtsi b/arch/arm/boot/dts/nxp/imx/imx6ul-imx6ull-var-wm8731.dtsi
> new file mode 100644
> index 0000000000000..ed9af0a39714c
> --- /dev/null
> +++ b/arch/arm/boot/dts/nxp/imx/imx6ul-imx6ull-var-wm8731.dtsi
> @@ -0,0 +1,50 @@
> +// SPDX-License-Identifier: GPL-2.0+
> +/*
> + * Copyright (C) 2026 Variscite Ltd. - https://www.variscite.com
> + */
> +
> +#include "imx6ul-var-som-audio.dtsi"
> +
> +/ {
> +	sound {
> +		compatible = "simple-audio-card";
> +		simple-audio-card,bitclock-master = <&sound_master>;
> +		simple-audio-card,format = "i2s";
> +		simple-audio-card,frame-master = <&sound_master>;
> +		simple-audio-card,name = "wm8731audio";
> +		simple-audio-card,routing =
> +			"Headphone Jack", "RHPOUT",
> +			"Headphone Jack", "LHPOUT",
> +			"LLINEIN", "Line Jack",
> +			"RLINEIN", "Line Jack",
> +			"MICIN", "Mic Bias",
> +			"Mic Bias", "Mic Jack";

[Severity: High]
Does this routing reverse the logical signal flow for the microphone?

The simple-audio-card,routing property expects pairs in the format of
{"sink", "source"}.

In the DART WM8904 wrapper also added in this patch, the microphone routing is
correctly set up with audio flowing from the jack to the codec input, and bias
flowing from the codec to the jack:

    "IN2L", "Microphone Jack",
    "Microphone Jack", "MICBIAS"

However, the WM8731 configuration here uses "MICIN" as the sink for "Mic Bias",
and "Mic Bias" as the sink for "Mic Jack". This appears to treat the bias as
an audio source for the input pin, and the jack as a source for the bias.

Could this reversed routing violate DAPM semantics and prevent microphone audio
from being properly captured?

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/cover.1791487179.git.stefano.r@variscite.com?part=7