ASoC: codecs: wsa884x: Allow sharing reset GPIO

On some boards with multiple WSA8840/WSA8845 speakers, the reset
(shutdown) GPIO is shared between two speakers.  Use the reset
controller framework and its "reset-gpio" driver to handle this case.
This allows bring-up and proper handling of all WSA884x speakers on
X1E80100-CRD board.

Cc: Bartosz Golaszewski <brgl@bgdev.pl>
Cc: Sean Anderson <sean.anderson@seco.com>
Reviewed-by: Philipp Zabel <p.zabel@pengutronix.de>
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://msgid.link/r/20240129115216.96479-7-krzysztof.kozlowski@linaro.org
Signed-off-by: Mark Brown <broonie@kernel.org>

sound/soc/codecs/wsa884x.c

@@ -13,6 +13,7 @@
 #include <linux/pm_runtime.h>
 #include <linux/regmap.h>
 #include <linux/regulator/consumer.h>
+#include <linux/reset.h>
 #include <linux/slab.h>
 #include <linux/soundwire/sdw.h>
 #include <linux/soundwire/sdw_registers.h>
@@ -699,6 +700,7 @@ struct wsa884x_priv {
 	struct sdw_stream_runtime *sruntime;
 	struct sdw_port_config port_config[WSA884X_MAX_SWR_PORTS];
 	struct gpio_desc *sd_n;
+	struct reset_control *sd_reset;
 	bool port_prepared[WSA884X_MAX_SWR_PORTS];
 	bool port_enable[WSA884X_MAX_SWR_PORTS];
 	unsigned int variant;
@@ -1799,16 +1801,50 @@ static struct snd_soc_dai_driver wsa884x_dais[] = {
 	},
 };
 
-static void wsa884x_gpio_powerdown(void *data)
+static void wsa884x_reset_powerdown(void *data)
 {
-	gpiod_direction_output(data, 1);
+	struct wsa884x_priv *wsa884x = data;
+
+	if (wsa884x->sd_reset)
+		reset_control_assert(wsa884x->sd_reset);
+	else
+		gpiod_direction_output(wsa884x->sd_n, 1);
+}
+
+static void wsa884x_reset_deassert(struct wsa884x_priv *wsa884x)
+{
+	if (wsa884x->sd_reset)
+		reset_control_deassert(wsa884x->sd_reset);
+	else
+		gpiod_direction_output(wsa884x->sd_n, 0);
 }
 
 static void wsa884x_regulator_disable(void *data)
 {
 	regulator_bulk_disable(WSA884X_SUPPLIES_NUM, data);
 }
 
+static int wsa884x_get_reset(struct device *dev, struct wsa884x_priv *wsa884x)
+{
+	wsa884x->sd_reset = devm_reset_control_get_optional_shared(dev, NULL);
+	if (IS_ERR(wsa884x->sd_reset))
+		return dev_err_probe(dev, PTR_ERR(wsa884x->sd_reset),
+				     "Failed to get reset\n");
+	else if (wsa884x->sd_reset)
+		return 0;
+	/*
+	 * else: NULL, so use the backwards compatible way for powerdown-gpios,
+	 * which does not handle sharing GPIO properly.
+	 */
+	wsa884x->sd_n = devm_gpiod_get_optional(dev, "powerdown",
+						GPIOD_OUT_HIGH);
+	if (IS_ERR(wsa884x->sd_n))
+		return dev_err_probe(dev, PTR_ERR(wsa884x->sd_n),
+				     "Shutdown Control GPIO not found\n");
+
+	return 0;
+}
+
 static int wsa884x_probe(struct sdw_slave *pdev,
 			 const struct sdw_device_id *id)
 {
@@ -1838,11 +1874,9 @@ static int wsa884x_probe(struct sdw_slave *pdev,
 	if (ret)
 		return ret;
 
-	wsa884x->sd_n = devm_gpiod_get_optional(dev, "powerdown",
-						GPIOD_OUT_HIGH);
-	if (IS_ERR(wsa884x->sd_n))
-		return dev_err_probe(dev, PTR_ERR(wsa884x->sd_n),
-				     "Shutdown Control GPIO not found\n");
+	ret = wsa884x_get_reset(dev, wsa884x);
+	if (ret)
+		return ret;
 
 	dev_set_drvdata(dev, wsa884x);
 	wsa884x->slave = pdev;
@@ -1858,9 +1892,8 @@ static int wsa884x_probe(struct sdw_slave *pdev,
 	pdev->prop.sink_dpn_prop = wsa884x_sink_dpn_prop;
 	pdev->prop.scp_int1_mask = SDW_SCP_INT1_BUS_CLASH | SDW_SCP_INT1_PARITY;
 
-	/* Bring out of reset */
-	gpiod_direction_output(wsa884x->sd_n, 0);
-	ret = devm_add_action_or_reset(dev, wsa884x_gpio_powerdown, wsa884x->sd_n);
+	wsa884x_reset_deassert(wsa884x);
+	ret = devm_add_action_or_reset(dev, wsa884x_reset_powerdown, wsa884x);
 	if (ret)
 		return ret;