phy: renesas: rcar-gen3-usb2: Use mux-state for phyrst management

Add support for selecting the phyrst mux-state using the Linux mux
subsystem in the R-Car Gen3 USB2 PHY driver. This ensures correct hardware
initialization and integration with systems utilizing the mux-state device
tree property.

A temporary wrapper for optional muxes is introduced until native support
is available in the multiplexer subsystem.

Signed-off-by: Tommaso Merciai <[e-mail]>
Link: https://patch.msgid.link/80aafdb236[e-mail]
Signed-off-by: Vinod Koul <[e-mail]>

drivers/phy/renesas/Kconfig

···
 	depends on EXTCON || !EXTCON # if EXTCON=m, this cannot be built-in
 	depends on USB_SUPPORT
 	select GENERIC_PHY
+	select MULTIPLEXER
 	select USB_COMMON
 	help
 	  Support for USB 2.0 PHY found on Renesas R-Car generation 3 SoCs.

drivers/phy/renesas/phy-rcar-gen3-usb2.c

···
 #include <linux/io.h>
 #include <linux/module.h>
 #include <linux/mutex.h>
+#include <linux/mux/consumer.h>
 #include <linux/of.h>
 #include <linux/phy/phy.h>
 #include <linux/platform_device.h>
···
 	return rcar_gen3_phy_usb2_vbus_regulator_get_exclusive_enable(channel, enable);
 }
 
+/* Temporary wrapper until the multiplexer subsystem supports optional muxes */
+static inline struct mux_state *
+devm_mux_state_get_optional(struct device *dev, const char *mux_name)
+{
+	if (!of_property_present(dev->of_node, "mux-states"))
+		return NULL;
+
+	return devm_mux_state_get(dev, mux_name);
+}
+
+static void rcar_gen3_phy_mux_state_deselect(void *data)
+{
+	mux_state_deselect(data);
+}
+
 static int rcar_gen3_phy_usb2_probe(struct platform_device *pdev)
 {
 	struct device *dev = &pdev->dev;
 	struct rcar_gen3_chan *channel;
 	struct phy_provider *provider;
+	struct mux_state *mux_state;
 	int ret = 0, i, irq;
 
 	if (!dev->of_node) {
···
 		channel->rphys[i].ch = channel;
 		channel->rphys[i].int_enable_bits = rcar_gen3_int_enable[i];
 		phy_set_drvdata(channel->rphys[i].phy, &channel->rphys[i]);
+	}
+
+	mux_state = devm_mux_state_get_optional(dev, NULL);
+	if (IS_ERR(mux_state))
+		return PTR_ERR(mux_state);
+	if (mux_state) {
+		ret = mux_state_select(mux_state);
+		if (ret)
+			return dev_err_probe(dev, ret, "Failed to select USB mux\n");
+
+		ret = devm_add_action_or_reset(dev, rcar_gen3_phy_mux_state_deselect,
+					       mux_state);
+		if (ret)
+			return dev_err_probe(dev, ret,
+					     "Failed to register USB mux state deselect\n");
 	}
 
 	if (channel->phy_data->no_adp_ctrl && channel->is_otg_channel) {