[PATCH 2/2] ASoC: max98927: Add reset-gpio support

[Cheng-Yi Chiang <cychiang@chromium.org>]

Toggle reset line in max98927_i2c_probe.
Use a list to store max98927 instances so we do not toggle reset line
again if more than one instances share the same reset line.

Signed-off-by: Cheng-Yi Chiang <cychiang@chromium.org>
---
 sound/soc/codecs/max98927.c | 78 +++++++++++++++++++++++++++++++++++++++++++++
 sound/soc/codecs/max98927.h |  2 ++
 2 files changed, 80 insertions(+)

diff --git a/sound/soc/codecs/max98927.c b/sound/soc/codecs/max98927.c
index 941712058a8f5..789b27cdfd9e0 100644
--- a/sound/soc/codecs/max98927.c
+++ b/sound/soc/codecs/max98927.c
@@ -11,6 +11,7 @@
  */
 
 #include <linux/acpi.h>
+#include <linux/delay.h>
 #include <linux/i2c.h>
 #include <linux/module.h>
 #include <linux/regmap.h>
@@ -24,6 +25,11 @@
 #include <sound/tlv.h>
 #include "max98927.h"
 
+#define MAX98927_MIN_RESET_US 1
+#define MAX98927_RELEASE_RESET_DELAY_US 500
+
+static LIST_HEAD(reset_list);
+
 static struct reg_default max98927_reg[] = {
 	{MAX98927_R0001_INT_RAW1,  0x00},
 	{MAX98927_R0002_INT_RAW2,  0x00},
@@ -877,6 +883,54 @@ static void max98927_slot_config(struct i2c_client *i2c,
 		max98927->i_l_slot = 1;
 }
 
+static int max98927_i2c_toggle_reset(struct device *dev,
+				     struct max98927_priv *max98927)
+{
+	/*
+	 * If we do not have reset gpio, assume platform firmware
+	 * controls the regulator and toggles it for us.
+	 */
+	if (!max98927->reset_gpio)
+		return 0;
+
+	gpiod_set_value_cansleep(max98927->reset_gpio, 1);
+
+	/*
+	 * We need to wait a bit before we are allowed to release reset GPIO.
+	 */
+	usleep_range(MAX98927_MIN_RESET_US, MAX98927_MIN_RESET_US + 5);
+
+	gpiod_set_value_cansleep(max98927->reset_gpio, 0);
+
+	/*
+	 * We need to wait a bit before I2C communication is available.
+	 */
+	usleep_range(MAX98927_RELEASE_RESET_DELAY_US,
+		     MAX98927_RELEASE_RESET_DELAY_US + 5);
+
+	/*
+	 * Release reset GPIO because we are not going to use it.
+	 */
+	devm_gpiod_put(dev, max98927->reset_gpio);
+
+	return 0;
+}
+
+static bool max98927_is_first_to_reset(struct max98927_priv *max98927)
+{
+	struct max98927_priv *p;
+
+	if (!max98927->reset_gpio)
+		return false;
+
+	list_for_each_entry(p, &reset_list, list) {
+		if (max98927->reset_gpio == p->reset_gpio)
+			return false;
+	}
+
+	return true;
+}
+
 static int max98927_i2c_probe(struct i2c_client *i2c,
 	const struct i2c_device_id *id)
 {
@@ -904,6 +958,28 @@ static int max98927_i2c_probe(struct i2c_client *i2c,
 	} else
 		max98927->interleave_mode = 0;
 
+	/* Gets optional GPIO for reset line. */
+	max98927->reset_gpio = devm_gpiod_get_optional(
+			&i2c->dev, "reset", GPIOD_OUT_LOW);
+	if (IS_ERR(max98927->reset_gpio)) {
+		ret = PTR_ERR(max98927->reset_gpio);
+		dev_err(&i2c->dev, "error getting reset gpio: %d\n", ret);
+		return ret;
+	}
+
+	/*
+	 * Only toggle reset line for the first instance when the
+	 * reset line is shared among instances. For example,
+	 * left and right amplifier share the same reset line, and
+	 * we should only toggle the reset line once.
+	 */
+	if (max98927_is_first_to_reset(max98927)) {
+		dev_info(&i2c->dev, "%s: toggle reset line\n", __func__);
+		ret = max98927_i2c_toggle_reset(&i2c->dev, max98927);
+		if (ret)
+			return ret;
+	}
+
 	/* regmap initialization */
 	max98927->regmap
 		= devm_regmap_init_i2c(i2c, &max98927_regmap);
@@ -934,6 +1010,8 @@ static int max98927_i2c_probe(struct i2c_client *i2c,
 	if (ret < 0)
 		dev_err(&i2c->dev, "Failed to register component: %d\n", ret);
 
+	list_add(&max98927->list, &reset_list);
+
 	return ret;
 }
 
diff --git a/sound/soc/codecs/max98927.h b/sound/soc/codecs/max98927.h
index 538992a238b28..d48f61f6c3ba5 100644
--- a/sound/soc/codecs/max98927.h
+++ b/sound/soc/codecs/max98927.h
@@ -275,5 +275,7 @@ struct max98927_priv {
 	unsigned int master;
 	unsigned int digital_gain;
 	bool tdm_mode;
+	struct gpio_desc *reset_gpio;
+	struct list_head list;
 };
 #endif
-- 
2.16.4