[RFC PATCH] ASoC: ak4458: use reset control instead of reset gpio

["Viorel Suman (OSS)" <viorel.suman@xxxxxxxxxxx>]

From: Viorel Suman <viorel.suman@xxxxxxx>

Using GPIO API seems not a way to go for the case
when the same reset GPIO is used to control several codecs.
For a such case we can use the "gpio-reset" driver
and the "shared" reset API to manage the reset GPIO -
to deassert the reset when the first codec is powered up
and assert it when there is no codec in use.
DTS is supposed to look as follows:

/ {
    ak4458_reset: gpio-reset {
       compatible = "gpio-reset";
       reset-gpios = <&pca6416 4 GPIO_ACTIVE_LOW>;
       #reset-cells = <0>;
       initially-in-reset;
    };
};

&i2c3 {
    pca6416: gpio@20 {
       compatible = "ti,tca6416";
       reg = <0x20>;
       gpio-controller;
       #gpio-cells = <2>;
    };

    ak4458_1: ak4458@10 {
       compatible = "asahi-kasei,ak4458";
       reg = <0x10>;
       resets = <&ak4458_reset>;
    };

    ak4458_2: ak4458@11 {
       compatible = "asahi-kasei,ak4458";
       reg = <0x11>;
       resets = <&ak4458_reset>;
    };

    ak4458_3: ak4458@12 {
       compatible = "asahi-kasei,ak4458";
       reg = <0x12>;
       resets = <&ak4458_reset>;
    };
};

Signed-off-by: Viorel Suman <viorel.suman@xxxxxxx>
---
 sound/soc/codecs/ak4458.c | 23 +++++++++++------------
 1 file changed, 11 insertions(+), 12 deletions(-)

diff --git a/sound/soc/codecs/ak4458.c b/sound/soc/codecs/ak4458.c
index 1010c9ee2e83..f27727cb1382 100644
--- a/sound/soc/codecs/ak4458.c
+++ b/sound/soc/codecs/ak4458.c
@@ -13,6 +13,7 @@
 #include <linux/of_gpio.h>
 #include <linux/pm_runtime.h>
 #include <linux/regulator/consumer.h>
+#include <linux/reset.h>
 #include <linux/slab.h>
 #include <sound/initval.h>
 #include <sound/pcm_params.h>
@@ -45,7 +46,7 @@ struct ak4458_priv {
 	const struct ak4458_drvdata *drvdata;
 	struct device *dev;
 	struct regmap *regmap;
-	struct gpio_desc *reset_gpiod;
+	struct reset_control *reset;
 	struct gpio_desc *mute_gpiod;
 	int digfil;	/* SSLOW, SD, SLOW bits */
 	int fs;		/* sampling rate */
@@ -597,17 +598,17 @@ static struct snd_soc_dai_driver ak4497_dai = {
 
 static void ak4458_power_off(struct ak4458_priv *ak4458)
 {
-	if (ak4458->reset_gpiod) {
-		gpiod_set_value_cansleep(ak4458->reset_gpiod, 0);
-		usleep_range(1000, 2000);
+	if (ak4458->reset) {
+		reset_control_assert(ak4458->reset);
+		msleep(20);
 	}
 }
 
 static void ak4458_power_on(struct ak4458_priv *ak4458)
 {
-	if (ak4458->reset_gpiod) {
-		gpiod_set_value_cansleep(ak4458->reset_gpiod, 1);
-		usleep_range(1000, 2000);
+	if (ak4458->reset) {
+		reset_control_deassert(ak4458->reset);
+		msleep(20);
 	}
 }
 
@@ -685,7 +686,6 @@ static int __maybe_unused ak4458_runtime_resume(struct device *dev)
 	if (ak4458->mute_gpiod)
 		gpiod_set_value_cansleep(ak4458->mute_gpiod, 1);
 
-	ak4458_power_off(ak4458);
 	ak4458_power_on(ak4458);
 
 	regcache_cache_only(ak4458->regmap, false);
@@ -771,10 +771,9 @@ static int ak4458_i2c_probe(struct i2c_client *i2c)
 
 	ak4458->drvdata = of_device_get_match_data(&i2c->dev);
 
-	ak4458->reset_gpiod = devm_gpiod_get_optional(ak4458->dev, "reset",
-						      GPIOD_OUT_LOW);
-	if (IS_ERR(ak4458->reset_gpiod))
-		return PTR_ERR(ak4458->reset_gpiod);
+	ak4458->reset = devm_reset_control_get_optional_shared(ak4458->dev, NULL);
+	if (IS_ERR(ak4458->reset))
+		return PTR_ERR(ak4458->reset);
 
 	ak4458->mute_gpiod = devm_gpiod_get_optional(ak4458->dev, "mute",
 						     GPIOD_OUT_LOW);
-- 
2.26.2