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ASoC: dt-bindings: Add support for the GPIOs driven amplifier

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Some amplifiers based on analog switches and op-amps can be present in
the audio path and can be driven by GPIOs in order to control their gain
value, their mute and/or bypass functions.

Those components needs to be viewed as audio components in order to be
fully integrated in the audio path.

gpio-audio-amp allows to consider these GPIO driven amplifiers as
auxiliary audio devices.

Signed-off-by: Herve Codina <herve.codina@bootlin.com>
Reviewed-by: Rob Herring (Arm) <robh@kernel.org>
Link: https://patch.msgid.link/20260513081702.317117-3-herve.codina@bootlin.com
Signed-off-by: Mark Brown <broonie@kernel.org>
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Herve Codina 2026-05-13 10:16:46 +02:00 committed by Mark Brown
parent 37dba38ac8
commit 04a1fe8e65
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Documentation/devicetree/bindings/sound/gpio-audio-amp.yaml Normal file
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# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
%YAML 1.2
---
$id: http://devicetree.org/schemas/sound/gpio-audio-amp.yaml#
$schema: http://devicetree.org/meta-schemas/core.yaml#
title: Audio amplifier driven by GPIOs
maintainers:
- Herve Codina <herve.codina@bootlin.com>
description: |
Audio GPIO amplifiers are driven by GPIO in order to control the gain value
of the amplifier, its mute function and/or its bypass function.
Those amplifiers are based on discrete components (analog switches, op-amps
and more) where some of them, mostly analog switches, are controlled by GPIOs
to adjust the gain value of the whole amplifier and/or to control
the mute and/or bypass function.
For instance, the following piece of hardware is a GPIO amplifier
+5VA
^
|\ |
| \
Vin >---------------------------|+ \
| +-------+-----> Vout
.--\/\/\/--+------------|- / |
| | | / |
v | |/ | |
GND o v |
\ GND |
gpio >-----------> \ |
o o |
| | |
| '--\/\/\/--. |
| +--\/\/\/--'
'---------------'
properties:
compatible:
oneOf:
- const: gpio-audio-amp-mono
description:
A single channel amplifier. All features apply to this sole channel.
- const: gpio-audio-amp-stereo
description:
A dual channel amplifier (left and right). All features apply to both
channels producing the same effect on both channels at the same time.
vdd-supply:
description: Main power supply of the amplifier
vddio-supply:
description: Power supply related to the control path
vdda1-supply:
description: Analog power supply
vdda2-supply:
description: Additional analog power supply
mute-gpios:
description: GPIO to control the mute function
maxItems: 1
bypass-gpios:
description: GPIO to control the bypass function
maxItems: 1
gain-gpios:
description: |
GPIOs to control the amplifier gain
The gain value is computed from GPIOs value from 0 to 2^N-1 with N the
number of GPIO described. The first GPIO described is the lsb of the gain
value.
For instance assuming 2 gpios
gain-gpios = <&gpio1 GPIO_ACTIVE_HIGH> <&gpio2 GPIO_ACTIVE_HIGH>;
The gain value will be the following:
gpio1 | gpio2 | gain
------+-------+-----
0 | 0 | 0b00 -> 0
1 | 0 | 0b01 -> 1
0 | 1 | 0b10 -> 2
1 | 1 | 0b11 -> 3
------+-------+-----
Note: The gain value, bits set to 1 or 0, indicate the state active (bit
set) or the state inactive (bit unset) of the related GPIO. The
physical voltage corresponding to this active/inactive state is
given by the GPIO_ACTIVE_HIGH and GPIO_ACTIVE_LOW flags.
minItems: 1
maxItems: 16
gain-ranges:
$ref: /schemas/types.yaml#/definitions/int32-matrix
description: |
A list of one or more ranges of possible values. Each range is defined by
the first and last point in the range. Each point is defined by the pair
(GPIOs value, Gain in 0.01 dB unit).
Ranges can be contiguous or holes can be present between ranges if some
gpios value should not be used. Also in a range the first point and the
last point can be identical. In that case, the range contains only one
item, the given point.
items:
items:
- description: GPIOs value of the first point in the range
- description: Gain in 0.01 dB unit of the first point in the range
- description: GPIOs value of the last point in the range
- description: Gain in 0.01 dB unit of the last point in the range
description: |
A range defines a linear function (linear in dB) from the first point
to the last point, both included. The number of items in the range is
N = abs(first_point.gpio_value - last_point.gpio_value) + 1
It allows to define the gain range from the first_point.gain to
the last_point.gain, both points included.
Gain (0.01 dB unit)
^
| last
+- - - - - - - - - - + point
| + .
| + .
| + .
+- - - - + .
| first . .
| point . .
| . .
+--------+-----------+---> gpios
value
Note: Even if first_point.gpio_value is lower than last_point.gpio_value
and first_point.gain is lower than last_point.gain in the above
graphic, all combination of values are supported leading to an
increasing or a decreasing linear segment.
minItems: 1
maxItems: 65536
gain-labels:
$ref: /schemas/types.yaml#/definitions/string-array
minItems: 2
maxItems: 65536
description: |
List of the gain labels attached to the combination of GPIOs controlling
the gain. The first label is related to the gain value 0, the second label
is related to the gain value 1 and so on.
With 2 GPIOs controlling the gain, GPIOs value can be 0, 1, 2 and 3.
Assuming that gain value set the hardware according to the following
table:
GPIOs | Hardware
value | amplification
------+--------------
0 | Low
1 | Middle
2 | High
3 | Max
------+--------------
The description using gain labels can be:
gain-labels = "Low", "Middle", "High", "Max";
dependencies:
gain-ranges: [ gain-gpios ]
gain-labels: [ gain-gpios ]
required:
- compatible
- vdd-supply
anyOf:
- required:
- gain-gpios
- required:
- mute-gpios
- required:
- bypass-gpios
allOf:
- $ref: component-common.yaml#
- if:
required:
- gain-ranges
then:
properties:
gain-labels: false
- if:
required:
- gain-labels
then:
properties:
gain-ranges: false
unevaluatedProperties: false
examples:
- |
#include <dt-bindings/gpio/gpio.h>
/* Gain controlled by gpios */
amplifier-0 {
compatible = "gpio-audio-amp-mono";
vdd-supply = <&regulator>;
gain-gpios = <&gpio 0 GPIO_ACTIVE_HIGH>, <&gpio 1 GPIO_ACTIVE_HIGH>;
};
/* Gain controlled by gpio using a simple range on a stereo amplifier */
amplifier-1 {
compatible = "gpio-audio-amp-stereo";
vdd-supply = <&regulator>;
gain-gpios = <&gpio 0 GPIO_ACTIVE_HIGH>, <&gpio 1 GPIO_ACTIVE_HIGH>;
gain-ranges = <0 (-300) 3 600>;
};
/* Gain controlled by gpio with labels */
amplifier-3 {
compatible = "gpio-audio-amp-mono";
vdd-supply = <&regulator>;
gain-gpios = <&gpio 0 GPIO_ACTIVE_HIGH>;
gain-labels = "Low", "High";
};
/* A mutable stereo amplifier without any gain control */
amplifier-4 {
compatible = "gpio-audio-amp-stereo";
vdd-supply = <&regulator>;
mute-gpios = <&gpio 0 GPIO_ACTIVE_HIGH>;
};
/*
* Several supplies, gain controlled using more complex ranges, mute and
* bypass.
*
* Assuming 3 gpios for controlling the gain with the following table
* gpios value Gain
* 0b000 Do not use (gpios value not allowed)
* 0b001 - 3dB
* 0b010 + 3dB
* 0b011 + 10dB
* 0b100 Do not use (gpios value not allowed)
* 0b101 + 6dB
* 0b110 + 7dB
* 0b111 + 8dB
*/
amplifier-5 {
compatible = "gpio-audio-amp-mono";
vdd-supply = <&regulator>;
vddio-supply = <&regulator1>;
vdda1-supply = <&regulator2>;
gain-gpios = <&gpio 0 GPIO_ACTIVE_HIGH>,
<&gpio 1 GPIO_ACTIVE_HIGH>,
<&gpio 2 GPIO_ACTIVE_HIGH>;
gain-ranges = <1 (-300) 2 300>,
<3 1000 3 1000>,
<5 600 7 800>;
mute-gpios = <&gpio 3 GPIO_ACTIVE_HIGH>;
bypass-gpios = <&gpio 4 GPIO_ACTIVE_HIGH>;
};
...