linux-kernel - Re: [PATCH 12/13] ASoC: dt-bindings: davinic-mcbsp: Add the 'ti,drive-dx' property

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Date: Tue, 19 Mar 2024 20:02:48 +0200
From: Péter Ujfalusi <peter.ujfalusi@...il.com>
To: Bastien Curutchet <bastien.curutchet@...tlin.com>,
 Liam Girdwood <lgirdwood@...il.com>, Mark Brown <broonie@...nel.org>,
 Rob Herring <robh+dt@...nel.org>,
 Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
 Conor Dooley <conor+dt@...nel.org>, Jaroslav Kysela <perex@...ex.cz>,
 Takashi Iwai <tiwai@...e.com>
Cc: linux-sound@...r.kernel.org, devicetree@...r.kernel.org,
 linux-kernel@...r.kernel.org, alsa-devel@...a-project.org,
 Thomas Petazzoni <thomas.petazzoni@...tlin.com>, herve.codina@...tlin.com,
 christophercordahi@...ometrics.ca
Subject: Re: [PATCH 12/13] ASoC: dt-bindings: davinic-mcbsp: Add the
 'ti,drive-dx' property



On 15/03/2024 13:27, Bastien Curutchet wrote:
> McBSP is able to handle capture and playback stream.
> The McBSP's DX pins that outputs serial data during playback streams can
> be used to output a chosen pattern during capture streams. For instance,
> this can be useful to drive an active-low signal during capture streams
> (by choosing <0> as pattern)

or configure the MCBSPx.DX pin as GPO and use it as a GPIO?

Quite novel use of the hardware, no doubt about it. If you don't have
DMA servicing the TX, it will just re-transmit the word from from the
DXR register when the transmitter is pulled out of reset.

Interesting, but I'm not sure if this belongs to DT.

> Add a 'ti,drive-dx' property that can be used to repeatedly output a
> chosen pattern on DX pin while capture stream is ON.
> 
> Signed-off-by: Bastien Curutchet <bastien.curutchet@...tlin.com>
> ---
>  Documentation/devicetree/bindings/sound/davinci-mcbsp.yaml | 7 +++++++
>  1 file changed, 7 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/sound/davinci-mcbsp.yaml b/Documentation/devicetree/bindings/sound/davinci-mcbsp.yaml
> index d8d4e7ea6e02..f4d1fc6bcd61 100644
> --- a/Documentation/devicetree/bindings/sound/davinci-mcbsp.yaml
> +++ b/Documentation/devicetree/bindings/sound/davinci-mcbsp.yaml
> @@ -80,6 +80,13 @@ properties:
>        Enable synchronisation error detections when an unexpected frame pulse is
>        received. If not present, unexpected frame pulses are ignored.
>  
> +  ti,drive-dx:
> +    $ref: /schemas/types.yaml#/definitions/uint32
> +    description:
> +      If the property is present, McBSP will repeatedly output the selected
> +      value on DX pin during capture streams. For instance, if set to 0, this
> +      can be used to drive an active-low signal.
> +
>  required:
>    - "#sound-dai-cells"
>    - compatible

-- 
Péter