drivers: net: phy: mdio-mux: Add support for Generic Mux controls

Add support for Generic Mux controls, when Mdio mux node is a consumer
of mux produced by some other device.

Signed-off-by: Pankaj Bansal <pankaj.bansal@nxp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/phy/Kconfig

@@ -87,6 +87,18 @@ config MDIO_BUS_MUX_MMIOREG
 
 	  Currently, only 8/16/32 bits registers are supported.
 
+config MDIO_BUS_MUX_MULTIPLEXER
+	tristate "MDIO bus multiplexer using kernel multiplexer subsystem"
+	depends on OF
+	select MULTIPLEXER
+	select MDIO_BUS_MUX
+	help
+	  This module provides a driver for MDIO bus multiplexer
+	  that is controlled via the kernel multiplexer subsystem. The
+	  bus multiplexer connects one of several child MDIO busses to
+	  a parent bus.  Child bus selection is under the control of
+	  the kernel multiplexer subsystem.
+
 config MDIO_CAVIUM
 	tristate
 

drivers/net/phy/Makefile

@@ -29,6 +29,7 @@ obj-$(CONFIG_MDIO_BUS_MUX)	+= mdio-mux.o
 obj-$(CONFIG_MDIO_BUS_MUX_BCM_IPROC)	+= mdio-mux-bcm-iproc.o
 obj-$(CONFIG_MDIO_BUS_MUX_GPIO)	+= mdio-mux-gpio.o
 obj-$(CONFIG_MDIO_BUS_MUX_MMIOREG) += mdio-mux-mmioreg.o
+obj-$(CONFIG_MDIO_BUS_MUX_MULTIPLEXER) += mdio-mux-multiplexer.o
 obj-$(CONFIG_MDIO_CAVIUM)	+= mdio-cavium.o
 obj-$(CONFIG_MDIO_GPIO)		+= mdio-gpio.o
 obj-$(CONFIG_MDIO_HISI_FEMAC)	+= mdio-hisi-femac.o

drivers/net/phy/mdio-mux-multiplexer.c

@@ -0,0 +1,122 @@
+// SPDX-License-Identifier: GPL-2.0+
+/* MDIO bus multiplexer using kernel multiplexer subsystem
+ *
+ * Copyright 2019 NXP
+ */
+
+#include <linux/platform_device.h>
+#include <linux/mdio-mux.h>
+#include <linux/module.h>
+#include <linux/mux/consumer.h>
+
+struct mdio_mux_multiplexer_state {
+	struct mux_control *muxc;
+	bool do_deselect;
+	void *mux_handle;
+};
+
+/**
+ * mdio_mux_multiplexer_switch_fn - This function is called by the mdio-mux
+ *                                  layer when it thinks the mdio bus
+ *                                  multiplexer needs to switch.
+ * @current_child:  current value of the mux register.
+ * @desired_child: value of the 'reg' property of the target child MDIO node.
+ * @data: Private data used by this switch_fn passed to mdio_mux_init function
+ *        via mdio_mux_init(.., .., .., .., data, ..).
+ *
+ * The first time this function is called, current_child == -1.
+ * If current_child == desired_child, then the mux is already set to the
+ * correct bus.
+ */
+static int mdio_mux_multiplexer_switch_fn(int current_child, int desired_child,
+					  void *data)
+{
+	struct platform_device *pdev;
+	struct mdio_mux_multiplexer_state *s;
+	int ret = 0;
+
+	pdev = (struct platform_device *)data;
+	s = platform_get_drvdata(pdev);
+
+	if (!(current_child ^ desired_child))
+		return 0;
+
+	if (s->do_deselect)
+		ret = mux_control_deselect(s->muxc);
+	if (ret) {
+		dev_err(&pdev->dev, "mux_control_deselect failed in %s: %d\n",
+			__func__, ret);
+		return ret;
+	}
+
+	ret =  mux_control_select(s->muxc, desired_child);
+	if (!ret) {
+		dev_dbg(&pdev->dev, "%s %d -> %d\n", __func__, current_child,
+			desired_child);
+		s->do_deselect = true;
+	} else {
+		s->do_deselect = false;
+	}
+
+	return ret;
+}
+
+static int mdio_mux_multiplexer_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct mdio_mux_multiplexer_state *s;
+	int ret = 0;
+
+	s = devm_kzalloc(&pdev->dev, sizeof(*s), GFP_KERNEL);
+	if (!s)
+		return -ENOMEM;
+
+	s->muxc = devm_mux_control_get(dev, NULL);
+	if (IS_ERR(s->muxc)) {
+		ret = PTR_ERR(s->muxc);
+		if (ret != -EPROBE_DEFER)
+			dev_err(&pdev->dev, "Failed to get mux: %d\n", ret);
+		return ret;
+	}
+
+	platform_set_drvdata(pdev, s);
+
+	ret = mdio_mux_init(&pdev->dev, pdev->dev.of_node,
+			    mdio_mux_multiplexer_switch_fn, &s->mux_handle,
+			    pdev, NULL);
+
+	return ret;
+}
+
+static int mdio_mux_multiplexer_remove(struct platform_device *pdev)
+{
+	struct mdio_mux_multiplexer_state *s = platform_get_drvdata(pdev);
+
+	mdio_mux_uninit(s->mux_handle);
+
+	if (s->do_deselect)
+		mux_control_deselect(s->muxc);
+
+	return 0;
+}
+
+static const struct of_device_id mdio_mux_multiplexer_match[] = {
+	{ .compatible = "mdio-mux-multiplexer", },
+	{},
+};
+MODULE_DEVICE_TABLE(of, mdio_mux_multiplexer_match);
+
+static struct platform_driver mdio_mux_multiplexer_driver = {
+	.driver = {
+		.name		= "mdio-mux-multiplexer",
+		.of_match_table	= mdio_mux_multiplexer_match,
+	},
+	.probe		= mdio_mux_multiplexer_probe,
+	.remove		= mdio_mux_multiplexer_remove,
+};
+
+module_platform_driver(mdio_mux_multiplexer_driver);
+
+MODULE_DESCRIPTION("MDIO bus multiplexer using kernel multiplexer subsystem");
+MODULE_AUTHOR("Pankaj Bansal <pankaj.bansal@nxp.com>");
+MODULE_LICENSE("GPL");