ASoC: codecs: Add Awinic AW8738 audio amplifier driver

The Awinic AW8738 is a simple audio amplifier using a single GPIO.
The main difference to simple-amplifier is that there is a "one-wire
pulse control" that allows configuring the amplifier to one of a few
pre-defined modes. This can be used to configure the speaker-guard
function (primarily the power limit for the amplifier).

Add a simple driver that allows setting it up in the device tree
with a specified mode number.
Signed-off-by: Jonathan Albrieux <jonathan.albrieux@gmail.com>
Co-developed-by: Stephan Gerhold <stephan@gerhold.net>
Signed-off-by: Stephan Gerhold <stephan@gerhold.net>
Link: https://lore.kernel.org/r/20220304102452.26856-3-stephan@gerhold.netSigned-off-by: Mark Brown <broonie@kernel.org>

sound/soc/codecs/Kconfig

@@ -53,6 +53,7 @@ config SND_SOC_ALL_CODECS
 	imply SND_SOC_AK5558
 	imply SND_SOC_ALC5623
 	imply SND_SOC_ALC5632
+	imply SND_SOC_AW8738
 	imply SND_SOC_BT_SCO
 	imply SND_SOC_BD28623
 	imply SND_SOC_CQ0093VC
@@ -579,6 +580,15 @@ config SND_SOC_ALC5632
 	tristate
 	depends on I2C
 
+config SND_SOC_AW8738
+	tristate "Awinic AW8738 Audio Amplifier"
+	select GPIOLIB
+	help
+	  Enable support for the Awinic AW8738 audio amplifier (or similar).
+	  The driver supports simple audio amplifiers similar to
+	  SND_SOC_SIMPLE_AMPLIFIER, but additionally allows setting the
+	  operation mode using the Awinic-specific one-wire pulse control.
+
 config SND_SOC_BD28623
 	tristate "ROHM BD28623 CODEC"
 	help

sound/soc/codecs/Makefile

@@ -45,6 +45,7 @@ snd-soc-ak4671-objs := ak4671.o
 snd-soc-ak5386-objs := ak5386.o
 snd-soc-ak5558-objs := ak5558.o
 snd-soc-arizona-objs := arizona.o arizona-jack.o
+snd-soc-aw8738-objs := aw8738.o
 snd-soc-bd28623-objs := bd28623.o
 snd-soc-bt-sco-objs := bt-sco.o
 snd-soc-cpcap-objs := cpcap.o
@@ -388,6 +389,7 @@ obj-$(CONFIG_SND_SOC_AK5558)	+= snd-soc-ak5558.o
 obj-$(CONFIG_SND_SOC_ALC5623)    += snd-soc-alc5623.o
 obj-$(CONFIG_SND_SOC_ALC5632)	+= snd-soc-alc5632.o
 obj-$(CONFIG_SND_SOC_ARIZONA)	+= snd-soc-arizona.o
+obj-$(CONFIG_SND_SOC_AW8738)	+= snd-soc-aw8738.o
 obj-$(CONFIG_SND_SOC_BD28623)	+= snd-soc-bd28623.o
 obj-$(CONFIG_SND_SOC_BT_SCO)	+= snd-soc-bt-sco.o
 obj-$(CONFIG_SND_SOC_CQ0093VC) += snd-soc-cq93vc.o

sound/soc/codecs/aw8738.c

+// SPDX-License-Identifier: GPL-2.0-only
+
+#include <linux/gpio/consumer.h>
+#include <linux/module.h>
+#include <linux/regulator/consumer.h>
+#include <sound/soc.h>
+
+struct aw8738_priv {
+	struct gpio_desc *gpiod_mode;
+	unsigned int mode;
+};
+
+static int aw8738_drv_event(struct snd_soc_dapm_widget *w,
+			    struct snd_kcontrol *kcontrol, int event)
+{
+	struct snd_soc_component *c = snd_soc_dapm_to_component(w->dapm);
+	struct aw8738_priv *aw = snd_soc_component_get_drvdata(c);
+	int i;
+
+	switch (event) {
+	case SND_SOC_DAPM_POST_PMU:
+		for (i = 0; i < aw->mode; i++) {
+			gpiod_set_value_cansleep(aw->gpiod_mode, 0);
+			udelay(2);
+			gpiod_set_value_cansleep(aw->gpiod_mode, 1);
+			udelay(2);
+		}
+		msleep(40);
+		break;
+	case SND_SOC_DAPM_PRE_PMD:
+		gpiod_set_value_cansleep(aw->gpiod_mode, 0);
+		usleep_range(1000, 2000);
+		break;
+	default:
+		WARN(1, "Unexpected event");
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
+static const struct snd_soc_dapm_widget aw8738_dapm_widgets[] = {
+	SND_SOC_DAPM_INPUT("IN"),
+	SND_SOC_DAPM_OUT_DRV_E("DRV", SND_SOC_NOPM, 0, 0, NULL, 0, aw8738_drv_event,
+			       SND_SOC_DAPM_POST_PMU | SND_SOC_DAPM_PRE_PMD),
+	SND_SOC_DAPM_OUTPUT("OUT"),
+};
+
+static const struct snd_soc_dapm_route aw8738_dapm_routes[] = {
+	{ "DRV", NULL, "IN" },
+	{ "OUT", NULL, "DRV" },
+};
+
+static const struct snd_soc_component_driver aw8738_component_driver = {
+	.dapm_widgets = aw8738_dapm_widgets,
+	.num_dapm_widgets = ARRAY_SIZE(aw8738_dapm_widgets),
+	.dapm_routes = aw8738_dapm_routes,
+	.num_dapm_routes = ARRAY_SIZE(aw8738_dapm_routes),
+};
+
+static int aw8738_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct aw8738_priv *aw;
+	int ret;
+
+	aw = devm_kzalloc(dev, sizeof(*aw), GFP_KERNEL);
+	if (!aw)
+		return -ENOMEM;
+	platform_set_drvdata(pdev, aw);
+
+	aw->gpiod_mode = devm_gpiod_get(dev, "mode", GPIOD_OUT_LOW);
+	if (IS_ERR(aw->gpiod_mode))
+		return dev_err_probe(dev, PTR_ERR(aw->gpiod_mode),
+				     "Failed to get 'mode' gpio");
+
+	ret = device_property_read_u32(dev, "awinic,mode", &aw->mode);
+	if (ret)
+		return -EINVAL;
+
+	return devm_snd_soc_register_component(&pdev->dev,
+					       &aw8738_component_driver,
+					       NULL, 0);
+}
+
+#ifdef CONFIG_OF
+static const struct of_device_id aw8738_of_match[] = {
+	{ .compatible = "awinic,aw8738" },
+	{ }
+};
+MODULE_DEVICE_TABLE(of, aw8738_of_match);
+#endif
+
+static struct platform_driver aw8738_driver = {
+	.probe	= aw8738_probe,
+	.driver = {
+		.name = "aw8738",
+		.of_match_table = of_match_ptr(aw8738_of_match),
+	},
+};
+module_platform_driver(aw8738_driver);
+
+MODULE_DESCRIPTION("Awinic AW8738 Amplifier Driver");
+MODULE_LICENSE("GPL v2");