[PATCH v2 11/17] ASoC: simple-amplifier: gpio-audio-amp: Add support for mute gpio

Herve Codina
2026-04-29T07:44:40Z

A gpio can be used to control the amplifier mute feature.

Add support for this mute gpio.

Signed-off-by: Herve Codina <herve.codina@bootlin.com>
---
sound/soc/codecs/simple-amplifier.c | 127 +++++++++++++++++++++++++++-
1 file changed, 125 insertions(+), 2 deletions(-)

diff --git a/sound/soc/codecs/simple-amplifier.c b/sound/soc/codecs/simple-amplifier.c
index 537731996544..61d1cbb0661d 100644
--- a/sound/soc/codecs/simple-amplifier.c
+++ b/sound/soc/codecs/simple-amplifier.c
@@ -12,10 +12,18 @@
#include <linux/regulator/consumer.h>
#include <sound/soc.h>

+struct simple_amp_single {
+ struct gpio_desc *gpio;
+ bool is_inverted;
+ int kctrl_val;
+ const char *control_name;
+};
+
struct simple_amp_data {
unsigned int supports;
#define SIMPLE_AUDIO_SUPPORT_PGA BIT(0)
#define SIMPLE_AUDIO_SUPPORT_POWER_SUPPLIES BIT(1)
+#define SIMPLE_AUDIO_SUPPORT_MUTE BIT(2)

const struct snd_soc_dapm_widget *dapm_widgets;
unsigned int num_dapm_widgets;
@@ -26,6 +34,7 @@ struct simple_amp_data {
struct simple_amp {
const struct simple_amp_data *data;
struct gpio_desc *gpiod_enable;
+ struct simple_amp_single mute;
};

static int simple_amp_power_event(struct snd_soc_dapm_widget *w,
@@ -103,6 +112,78 @@ static const struct snd_soc_dapm_route simple_amp_stereo_pga_dapm_routes[] = {
{ "OUTR", NULL, "PGA" },
};

+static int simple_amp_single_kctrl_write_gpio(struct simple_amp_single *single,
+ int kctrl_val)
+{
+ int gpio_val;
+
+ gpio_val = single->is_inverted ? !kctrl_val : kctrl_val;
+
+ return gpiod_set_value_cansleep(single->gpio, gpio_val);
+}
+
+static int simple_amp_single_kctrl_info(struct snd_kcontrol *kcontrol,
+ struct snd_ctl_elem_info *uinfo)
+{
+ uinfo->count = 1;
+ uinfo->value.integer.min = 0;
+ uinfo->value.integer.max = 1;
+ uinfo->type = SNDRV_CTL_ELEM_TYPE_BOOLEAN;
+ return 0;
+}
+
+static int simple_amp_single_kctrl_get(struct snd_kcontrol *kcontrol,
+ struct snd_ctl_elem_value *ucontrol)
+{
+ struct simple_amp_single *single = (struct simple_amp_single *)kcontrol->private_value;
+
+ ucontrol->value.integer.value[0] = single->kctrl_val;
+
+ return 0;
+}
+
+static int simple_amp_single_kctrl_put(struct snd_kcontrol *kcontrol,
+ struct snd_ctl_elem_value *ucontrol)
+{
+ struct simple_amp_single *single = (struct simple_amp_single *)kcontrol->private_value;
+ int kctrl_val;
+ int err;
+
+ kctrl_val = ucontrol->value.integer.value[0];
+
+ if (kctrl_val == single->kctrl_val)
+ return 0;
+
+ err = simple_amp_single_kctrl_write_gpio(single, kctrl_val);
+ if (err)
+ return err;
+
+ single->kctrl_val = kctrl_val;
+
+ return 1; /* The value changed */
+}
+
+static int simple_amp_single_add_kcontrol(struct snd_soc_component *component,
+ struct simple_amp_single *single)
+{
+ struct snd_kcontrol_new control = {
+ .iface = SNDRV_CTL_ELEM_IFACE_MIXER,
+ .name = single->control_name,
+ .info = simple_amp_single_kctrl_info,
+ .get = simple_amp_single_kctrl_get,
+ .put = simple_amp_single_kctrl_put,
+ .private_value = (unsigned long)single,
+ };
+ int ret;
+
+ /* Be consistent between single->kctrl_val value and the GPIO value */
+ ret = simple_amp_single_kctrl_write_gpio(single, single->kctrl_val);
+ if (ret)
+ return ret;
+
+ return snd_soc_add_component_controls(component, &control, 1);
+}
+
static int simple_amp_add_basic_dapm(struct snd_soc_component *component)
{
struct snd_soc_dapm_context *dapm = snd_soc_component_to_dapm(component);
@@ -207,6 +288,21 @@ static int simple_amp_component_probe(struct snd_soc_component *component)
return ret;
}

+ if (simple_amp->mute.gpio) {
+ /*
+ * The name of the GPIO used is mute. According to this name, 1
+ * means muted and 0 means un-muted.
+ *
+ * An inversion is expected by ALSA. Indeed from ALSA point of
+ * view, 1 means 'on' (un-muted) and 0 means 'off' (muted).
+ */
+ simple_amp->mute.is_inverted = true;
+ simple_amp->mute.kctrl_val = 1; /* Un-muted */
+ ret = simple_amp_single_add_kcontrol(component, &simple_amp->mute);
+ if (ret)
+ return ret;
+ }
+
return 0;
}

@@ -214,10 +310,26 @@ static const struct snd_soc_component_driver simple_amp_component_driver = {
.probe = simple_amp_component_probe,
};

+static int simple_amp_parse_single_gpio(struct device *dev,
+ struct simple_amp_single *single,
+ const char *gpio_property)
+{
+ /* Start with the inactive value */
+ single->is_inverted = false;
+ single->kctrl_val = 0;
+ single->gpio = devm_gpiod_get_optional(dev, gpio_property, GPIOD_OUT_LOW);
+ if (IS_ERR(single->gpio))
+ return dev_err_probe(dev, PTR_ERR(single->gpio),
+ "Failed to get '%s' gpio\n",
+ gpio_property);
+ return 0;
+}
+
static int simple_amp_probe(struct platform_device *pdev)
{
struct device *dev = &pdev->dev;
struct simple_amp *simple_amp;
+ int ret;

simple_amp = devm_kzalloc(dev, sizeof(*simple_amp), GFP_KERNEL);
if (!simple_amp)
@@ -234,6 +346,15 @@ static int simple_amp_probe(struct platform_device *pdev)
return dev_err_probe(dev, PTR_ERR(simple_amp->gpiod_enable),
"Failed to get 'enable' gpio");

+ if (simple_amp->data->supports & SIMPLE_AUDIO_SUPPORT_MUTE) {
+ ret = simple_amp_parse_single_gpio(dev, &simple_amp->mute, "mute");
+ if (ret)
+ return ret;
+ }
+
+ /* Set controls name */
+ simple_amp->mute.control_name = "Switch";
+
return devm_snd_soc_register_component(dev,
&simple_amp_component_driver,
NULL, 0);
@@ -248,7 +369,8 @@ static const struct simple_amp_data simple_audio_amplifier_data = {

static const struct simple_amp_data simple_audio_mono_pga_data = {
.supports = SIMPLE_AUDIO_SUPPORT_PGA |
- SIMPLE_AUDIO_SUPPORT_POWER_SUPPLIES,
+ SIMPLE_AUDIO_SUPPORT_POWER_SUPPLIES |
+ SIMPLE_AUDIO_SUPPORT_MUTE,
.dapm_widgets = simple_amp_mono_pga_dapm_widgets,
.num_dapm_widgets = ARRAY_SIZE(simple_amp_mono_pga_dapm_widgets),
.dapm_routes = simple_amp_mono_pga_dapm_routes,
@@ -257,7 +379,8 @@ static const struct simple_amp_data simple_audio_mono_pga_data = {

static const struct simple_amp_data simple_audio_stereo_pga_data = {
.supports = SIMPLE_AUDIO_SUPPORT_PGA |
- SIMPLE_AUDIO_SUPPORT_POWER_SUPPLIES,
+ SIMPLE_AUDIO_SUPPORT_POWER_SUPPLIES |
+ SIMPLE_AUDIO_SUPPORT_MUTE,
.dapm_widgets = simple_amp_stereo_pga_dapm_widgets,
.num_dapm_widgets = ARRAY_SIZE(simple_amp_stereo_pga_dapm_widgets),
.dapm_routes = simple_amp_stereo_pga_dapm_routes,
--
2.53.0