ASoC: samsung: midas_wm1811: Add GPIO-based headset jack detection

Some Samsung devices that use the midas_wm1811 driver use a GPIO-based
method for detecting whether the headset jack is plugged in, as well as
detecting which headset buttons are pressed. There are two GPIOs:
a "headset detect" GPIO responsible for detecting jack insertion, and
a "headset key" GPIO which triggers when a button on the headset is
pressed. The plug type and the button pressed are determined based
on information from an ADC channel. The headset mic is enabled by a
headset mic bias regulator.

Add support for the GPIO-based headset jack detection mechanism,
and make it configurable from the device tree.

This implementation borrows somewhat from the aries_wm8994.c driver,
though there are a few changes to make the code cleaner, and to add
support for DT-based configuration.

Notably, a dependency on IIO is introduced, to accommodate the ADC
reading requirement.

Signed-off-by: Artur Weber <aweber.kernel@gmail.com>
Link: https://msgid.link/r/20240525-midas-wm1811-gpio-jack-v4-5-f488e03bd8c7@gmail.com
Signed-off-by: Mark Brown <broonie@kernel.org>

sound/soc/samsung/Kconfig

@@ -140,7 +140,7 @@ config SND_SOC_SAMSUNG_ARIES_WM8994
 
 config SND_SOC_SAMSUNG_MIDAS_WM1811
 	tristate "SoC I2S Audio support for Midas boards"
-	depends on SND_SOC_SAMSUNG
+	depends on SND_SOC_SAMSUNG && IIO
 	select SND_SAMSUNG_I2S
 	select SND_SOC_WM8994
 	help

sound/soc/samsung/midas_wm1811.c

@@ -7,7 +7,9 @@
 
 #include <linux/clk.h>
 #include <linux/gpio/consumer.h>
+#include <linux/iio/consumer.h>
 #include <linux/mfd/wm8994/registers.h>
+#include <linux/input-event-codes.h>
 #include <linux/module.h>
 #include <linux/of.h>
 #include <sound/jack.h>
@@ -28,6 +30,9 @@
 struct midas_priv {
 	struct gpio_desc *gpio_fm_sel;
 	struct gpio_desc *gpio_lineout_sel;
+	struct gpio_desc *gpio_headset_detect;
+	struct gpio_desc *gpio_headset_key;
+	struct iio_channel *adc_headset_detect;
 	unsigned int fll1_rate;
 
 	struct snd_soc_jack headset_jack;
@@ -44,6 +49,117 @@ static struct snd_soc_jack_pin headset_jack_pins[] = {
 	},
 };
 
+/*
+ * min_mv/max_mv values in this struct are set up based on DT values.
+ */
+static struct snd_soc_jack_zone headset_jack_zones[] = {
+	{ .jack_type = SND_JACK_HEADPHONE, },
+	{ .jack_type = SND_JACK_HEADSET, },
+	{ .jack_type = SND_JACK_HEADPHONE, },
+};
+
+/*
+ * This is used for manual detection in headset_key_check, we reuse the
+ * structure since it's convenient.
+ *
+ * min_mv/max_mv values in this struct are set up based on DT values.
+ */
+static struct snd_soc_jack_zone headset_key_zones[] = {
+	{ .jack_type = SND_JACK_BTN_0, },  /* Media */
+	{ .jack_type = SND_JACK_BTN_1, },  /* Volume Up */
+	{ .jack_type = SND_JACK_BTN_2, },  /* Volume Down */
+};
+
+static int headset_jack_check(void *data)
+{
+	struct snd_soc_component *codec = data;
+	struct snd_soc_dapm_context *dapm = snd_soc_component_get_dapm(codec);
+	struct midas_priv *priv = snd_soc_card_get_drvdata(codec->card);
+	int adc, ret;
+	int jack_type = 0;
+
+	if (!gpiod_get_value_cansleep(priv->gpio_headset_detect))
+		return 0;
+
+	/* Enable headset mic bias regulator so that the ADC reading works */
+	ret = snd_soc_dapm_force_enable_pin(dapm, "headset-mic-bias");
+	if (ret < 0) {
+		pr_err("%s: Failed to enable headset mic bias regulator (%d), assuming headphones\n",
+		       __func__, ret);
+		return SND_JACK_HEADPHONE;
+	}
+	snd_soc_dapm_sync(dapm);
+
+	/* Sleep for a small amount of time to get the value to stabilize */
+	msleep(20);
+
+	ret = iio_read_channel_processed(priv->adc_headset_detect, &adc);
+	if (ret) {
+		pr_err("%s: Failed to read ADC (%d), assuming headphones\n",
+		       __func__, ret);
+		jack_type = SND_JACK_HEADPHONE;
+		goto out;
+	}
+	pr_debug("%s: ADC value is %d\n", __func__, adc);
+
+	jack_type = snd_soc_jack_get_type(&priv->headset_jack, adc);
+
+out:
+	ret = snd_soc_dapm_disable_pin(dapm, "headset-mic-bias");
+	if (ret < 0)
+		pr_err("%s: Failed to disable headset mic bias regulator (%d)\n",
+		       __func__, ret);
+	snd_soc_dapm_sync(dapm);
+
+	return jack_type;
+}
+
+static int headset_key_check(void *data)
+{
+	struct snd_soc_component *codec = data;
+	struct midas_priv *priv = snd_soc_card_get_drvdata(codec->card);
+	int adc, i, ret;
+
+	if (!gpiod_get_value_cansleep(priv->gpio_headset_key))
+		return 0;
+
+	/* Filter out keypresses when 4 pole jack not detected */
+	if (!(priv->headset_jack.status & SND_JACK_MICROPHONE))
+		return 0;
+
+	ret = iio_read_channel_processed(priv->adc_headset_detect, &adc);
+	if (ret) {
+		pr_err("%s: Failed to read ADC (%d), can't detect key type\n",
+		       __func__, ret);
+		return 0;
+	}
+	pr_debug("%s: ADC value is %d\n", __func__, adc);
+
+	for (i = 0; i < ARRAY_SIZE(headset_key_zones); i++) {
+		if (adc >= headset_key_zones[i].min_mv &&
+		    adc <= headset_key_zones[i].max_mv) {
+			return headset_key_zones[i].jack_type;
+		}
+	}
+
+	return 0;
+}
+
+static struct snd_soc_jack_gpio headset_gpio[] = {
+	{
+		.name = "Headset Jack",
+		.report = SND_JACK_HEADSET,
+		.debounce_time = 150,
+		.jack_status_check = headset_jack_check,
+	},
+	{
+		.name = "Headset Key",
+		.report = SND_JACK_BTN_0 | SND_JACK_BTN_1 | SND_JACK_BTN_2,
+		.debounce_time = 30,
+		.jack_status_check = headset_key_check,
+	},
+};
+
 static int midas_start_fll1(struct snd_soc_pcm_runtime *rtd, unsigned int rate)
 {
 	struct snd_soc_card *card = rtd->card;
@@ -291,18 +407,67 @@ static int midas_late_probe(struct snd_soc_card *card)
 		return ret;
 	}
 
-	ret = snd_soc_card_jack_new_pins(card, "Headset",
-					 SND_JACK_HEADSET | SND_JACK_MECHANICAL |
-					 SND_JACK_BTN_0 | SND_JACK_BTN_1 | SND_JACK_BTN_2 |
-					 SND_JACK_BTN_3 | SND_JACK_BTN_4 | SND_JACK_BTN_5,
-					 &priv->headset_jack,
-					 headset_jack_pins,
-					 ARRAY_SIZE(headset_jack_pins));
-	if (ret)
-		return ret;
+	if (!priv->gpio_headset_detect) {
+		ret = snd_soc_card_jack_new_pins(card, "Headset",
+				 SND_JACK_HEADSET | SND_JACK_MECHANICAL |
+				 SND_JACK_BTN_0 | SND_JACK_BTN_1 |
+				 SND_JACK_BTN_2 | SND_JACK_BTN_3 |
+				 SND_JACK_BTN_4 | SND_JACK_BTN_5,
+				 &priv->headset_jack,
+				 headset_jack_pins,
+				 ARRAY_SIZE(headset_jack_pins));
+		if (ret)
+			return ret;
+
+		wm8958_mic_detect(aif1_dai->component, &priv->headset_jack,
+				  NULL, NULL, NULL, NULL);
+	} else {
+		/* Some devices (n8000, t310) use a GPIO to detect the jack. */
+		ret = snd_soc_card_jack_new_pins(card, "Headset",
+				SND_JACK_HEADSET | SND_JACK_BTN_0 |
+				SND_JACK_BTN_1 | SND_JACK_BTN_2,
+				&priv->headset_jack,
+				headset_jack_pins,
+				ARRAY_SIZE(headset_jack_pins));
+		if (ret) {
+			dev_err(card->dev,
+				"Failed to set up headset pins: %d\n", ret);
+			return ret;
+		}
+
+		ret = snd_soc_jack_add_zones(&priv->headset_jack,
+				ARRAY_SIZE(headset_jack_zones),
+				headset_jack_zones);
+		if (ret) {
+			dev_err(card->dev,
+				"Failed to set up headset zones: %d\n", ret);
+			return ret;
+		}
+
+		headset_gpio[0].data = aif1_dai->component;
+		headset_gpio[0].desc = priv->gpio_headset_detect;
+
+		headset_gpio[1].data = aif1_dai->component;
+		headset_gpio[1].desc = priv->gpio_headset_key;
+
+		snd_jack_set_key(priv->headset_jack.jack,
+				 SND_JACK_BTN_0, KEY_MEDIA);
+		snd_jack_set_key(priv->headset_jack.jack,
+				 SND_JACK_BTN_1, KEY_VOLUMEUP);
+		snd_jack_set_key(priv->headset_jack.jack,
+				 SND_JACK_BTN_2, KEY_VOLUMEDOWN);
+
+		ret = snd_soc_jack_add_gpios(&priv->headset_jack,
+				ARRAY_SIZE(headset_gpio),
+				headset_gpio);
+		if (ret)
+			dev_err(card->dev,
+				"Failed to set up headset jack GPIOs: %d\n",
+				ret);
+
+		return ret;
+	}
 
-	wm8958_mic_detect(aif1_dai->component, &priv->headset_jack,
-			  NULL, NULL, NULL, NULL);
 	return 0;
 }
 
@@ -411,6 +576,9 @@ static int midas_probe(struct platform_device *pdev)
 	struct snd_soc_card *card = &midas_card;
 	struct device *dev = &pdev->dev;
 	static struct snd_soc_dai_link *dai_link;
+	enum iio_chan_type channel_type;
+	u32 fourpole_threshold[2];
+	u32 button_threshold[3];
 	struct midas_priv *priv;
 	int ret, i;
 
@@ -434,6 +602,90 @@ static int midas_probe(struct platform_device *pdev)
 		return PTR_ERR(priv->gpio_lineout_sel);
 	}
 
+	priv->gpio_headset_detect = devm_gpiod_get_optional(dev,
+				"headset-detect", GPIOD_IN);
+	if (IS_ERR(priv->gpio_headset_detect))
+		return dev_err_probe(dev, PTR_ERR(priv->gpio_headset_detect),
+				     "Failed to get headset jack detect GPIO\n");
+
+	if (priv->gpio_headset_detect) {
+		priv->adc_headset_detect = devm_iio_channel_get(dev,
+							"headset-detect");
+		if (IS_ERR(priv->adc_headset_detect))
+			return dev_err_probe(dev,
+					     PTR_ERR(priv->adc_headset_detect),
+					     "Failed to get ADC channel\n");
+
+		ret = iio_get_channel_type(priv->adc_headset_detect,
+					   &channel_type);
+		if (ret) {
+			dev_err(dev, "Failed to get ADC channel type\n");
+			return ret;
+		}
+
+		if (channel_type != IIO_VOLTAGE) {
+			dev_err(dev, "ADC channel is not voltage\n");
+			return ret;
+		}
+
+		priv->gpio_headset_key = devm_gpiod_get(dev, "headset-key",
+							GPIOD_IN);
+		if (IS_ERR(priv->gpio_headset_key))
+			return dev_err_probe(dev,
+					     PTR_ERR(priv->gpio_headset_key),
+					     "Failed to get headset key GPIO\n");
+
+		ret = of_property_read_u32_array(dev->of_node,
+				"samsung,headset-4pole-threshold-microvolt",
+				fourpole_threshold,
+				ARRAY_SIZE(fourpole_threshold));
+		if (ret) {
+			dev_err(dev, "Failed to get 4-pole jack detection threshold\n");
+			return ret;
+		}
+
+		if (fourpole_threshold[0] > fourpole_threshold[1]) {
+			dev_err(dev, "Invalid 4-pole jack detection threshold value\n");
+			return -EINVAL;
+		}
+
+		headset_jack_zones[0].max_mv = (fourpole_threshold[0]);
+		headset_jack_zones[1].min_mv = (fourpole_threshold[0] + 1);
+
+		headset_jack_zones[1].max_mv = (fourpole_threshold[1]);
+		headset_jack_zones[2].min_mv = (fourpole_threshold[1] + 1);
+
+		ret = of_property_read_u32_array(dev->of_node,
+				"samsung,headset-button-threshold-microvolt",
+				button_threshold,
+				ARRAY_SIZE(button_threshold));
+		if (ret) {
+			dev_err(dev, "Failed to get headset button detection threshold\n");
+			return ret;
+		}
+
+		if (button_threshold[0] > button_threshold[1] ||
+		    button_threshold[1] > button_threshold[2]) {
+			dev_err(dev, "Invalid headset button detection threshold value\n");
+			return -EINVAL;
+		}
+
+		for (i = 0; i < 3; i++) {
+			if (i != 0 && button_threshold[i] <= 0) {
+				dev_err(dev, "Invalid headset button detection threshold value\n");
+				return -EINVAL;
+			}
+
+			headset_key_zones[i].min_mv = button_threshold[i];
+
+			if (i == 2)
+				headset_key_zones[i].max_mv = UINT_MAX;
+			else
+				headset_key_zones[i].max_mv = \
+						(button_threshold[i+1] - 1);
+		}
+	}
+
 	ret = snd_soc_of_parse_card_name(card, "model");
 	if (ret < 0) {
 		dev_err(dev, "Card name is not specified\n");