[PATCH 1/1] netdev/phy: add MDIO bus multiplexer driven by a regmap

[Pankaj Bansal <pankaj.bansal@nxp.com>]

Add support for an MDIO bus multiplexer controlled by a regmap
device, like an FPGA.

Tested on a NXP LX2160AQDS board which uses the "QIXIS" FPGA
attached to the i2c bus.

Signed-off-by: Pankaj Bansal <pankaj.bansal@nxp.com>
---
 drivers/net/phy/Makefile          |   2 +-
 drivers/net/phy/mdio-mux-regmap.c | 170 ++++++++++++++++++++++++++++
 include/linux/mdio-mux.h          |  20 ++++
 3 files changed, 191 insertions(+), 1 deletion(-)

diff --git a/drivers/net/phy/Makefile b/drivers/net/phy/Makefile
index f41b14115fde..16145973a42f 100644
--- a/drivers/net/phy/Makefile
+++ b/drivers/net/phy/Makefile
@@ -25,7 +25,7 @@ obj-$(CONFIG_PHYLIB)		+= libphy.o
 obj-$(CONFIG_MDIO_BCM_IPROC)	+= mdio-bcm-iproc.o
 obj-$(CONFIG_MDIO_BCM_UNIMAC)	+= mdio-bcm-unimac.o
 obj-$(CONFIG_MDIO_BITBANG)	+= mdio-bitbang.o
-obj-$(CONFIG_MDIO_BUS_MUX)	+= mdio-mux.o
+obj-$(CONFIG_MDIO_BUS_MUX)	+= mdio-mux.o mdio-mux-regmap.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
diff --git a/drivers/net/phy/mdio-mux-regmap.c b/drivers/net/phy/mdio-mux-regmap.c
new file mode 100644
index 000000000000..ca63a44da25f
--- /dev/null
+++ b/drivers/net/phy/mdio-mux-regmap.c
@@ -0,0 +1,170 @@
+// SPDX-License-Identifier: GPL-2.0+
+
+/* Simple regmap based MDIO MUX driver
+ *
+ * Copyright 2018 NXP
+ *
+ * Based on mdio-mux-mmioreg.c by Timur Tabi
+ *
+ * Author:
+ *     Pankaj Bansal <pankaj.ban...@nxp.com>
+ */
+
+#include <linux/platform_device.h>
+#include <linux/device.h>
+#include <linux/of_mdio.h>
+#include <linux/module.h>
+#include <linux/phy.h>
+#include <linux/mdio-mux.h>
+#include <linux/regmap.h>
+
+struct mdio_mux_regmap_state {
+	void		*mux_handle;
+	struct device	*dev;
+	struct regmap	*regmap;
+	u32		mux_reg;
+	u32		mask;
+};
+
+/* MDIO multiplexing switch function
+ *
+ * This function is called by the mdio-mux layer when it thinks the mdio bus
+ * multiplexer needs to switch.
+ *
+ * 'current_child' is the current value of the mux register (masked via
+ * s->mask).
+ *
+ * 'desired_child' is the value of the 'reg' property of the target child MDIO
+ * node.
+ *
+ * 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_regmap_switch_fn(int current_child, int desired_child,
+				     void *data)
+{
+	struct mdio_mux_regmap_state *s = data;
+	bool change;
+	int ret;
+
+	ret = regmap_update_bits_check(s->regmap,
+				       s->mux_reg,
+				       s->mask,
+				       desired_child,
+				       &change);
+
+	if (ret)
+		return ret;
+	if (change)
+		dev_dbg(s->dev, "%s %d -> %d\n", __func__, current_child,
+			desired_child);
+	return ret;
+}
+
+/**
+ * mdio_mux_regmap_init - control MDIO bus muxing using regmap constructs.
+ * @dev: device with which regmap construct is associated.
+ * @mux_node: mdio bus mux node that contains parent mdio bus phandle.
+ *	      This node also contains sub nodes, where each subnode denotes
+ *	      a child mdio bus. All the child mdio buses are muxed, i.e. at a
+ *	      time only one of the child mdio buses can be used.
+ * @data: to store the address of data allocated by this function
+ */
+int mdio_mux_regmap_init(struct device *dev,
+			 struct device_node *mux_node,
+			 void **data)
+{
+	struct device_node *child;
+	struct mdio_mux_regmap_state *s;
+	int ret;
+	u32 val;
+
+	dev_dbg(dev, "probing node %pOF\n", mux_node);
+
+	s = devm_kzalloc(dev, sizeof(*s), GFP_KERNEL);
+	if (!s)
+		return -ENOMEM;
+
+	s->regmap = dev_get_regmap(dev, NULL);
+	if (IS_ERR(s->regmap)) {
+		dev_err(dev, "Failed to get parent regmap\n");
+		return PTR_ERR(s->regmap);
+	}
+
+	ret = of_property_read_u32(mux_node, "reg", &s->mux_reg);
+	if (ret) {
+		dev_err(dev, "missing or invalid reg property\n");
+		return -ENODEV;
+	}
+
+	/* Test Register read write */
+	ret = regmap_read(s->regmap, s->mux_reg, &val);
+	if (ret) {
+		dev_err(dev, "error while reading reg\n");
+		return ret;
+	}
+
+	ret = regmap_write(s->regmap, s->mux_reg, val);
+	if (ret) {
+		dev_err(dev, "error while writing reg\n");
+		return ret;
+	}
+
+	ret = of_property_read_u32(mux_node, "mux-mask", &s->mask);
+	if (ret) {
+		dev_err(dev, "missing or invalid mux-mask property\n");
+		return -ENODEV;
+	}
+
+	/* Verify that the 'reg' property of each child MDIO bus does not
+	 * set any bits outside of the 'mask'.
+	 */
+	for_each_available_child_of_node(mux_node, child) {
+		ret = of_property_read_u32(child, "reg", &val);
+		if (ret) {
+			dev_err(dev, "mdio-mux child node %pOF is missing a 'reg' property\n", child);
+			of_node_put(child);
+			return -ENODEV;
+		}
+		if (val & ~s->mask) {
+			dev_err(dev, "mdio-mux child node %pOF has a 'reg' value with unmasked bits\n", child);
+			of_node_put(child);
+			return -ENODEV;
+		}
+	}
+
+	ret = mdio_mux_init(dev, mux_node, mdio_mux_regmap_switch_fn,
+			    &s->mux_handle, s, NULL);
+	if (ret) {
+		if (ret != -EPROBE_DEFER)
+			dev_err(dev, "failed to register mdio-mux bus %pOF\n", mux_node);
+		return ret;
+	}
+
+	*data = s;
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(mdio_mux_regmap_init);
+
+/**
+ * mdio_mux_regmap_uninit - relinquish the control of MDIO bus muxing using
+ *			    regmap constructs.
+ * @data: address of data allocated by mdio_mux_regmap_init
+ */
+int mdio_mux_regmap_uninit(void *data)
+{
+	struct mdio_mux_regmap_state *s = data;
+
+	mdio_mux_uninit(s->mux_handle);
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(mdio_mux_regmap_uninit);
+
+MODULE_AUTHOR("Pankaj Bansal <pankaj.bansal@nxp.com>");
+MODULE_DESCRIPTION("regmap based MDIO MUX driver");
+MODULE_LICENSE("GPL v2");
+
diff --git a/include/linux/mdio-mux.h b/include/linux/mdio-mux.h
index a5d58f221939..231cfa3ba429 100644
--- a/include/linux/mdio-mux.h
+++ b/include/linux/mdio-mux.h
@@ -29,4 +29,24 @@ int mdio_mux_init(struct device *dev,
 
 void mdio_mux_uninit(void *mux_handle);
 
+/**
+ * mdio_mux_regmap_init - control MDIO bus muxing using regmap constructs.
+ * @dev: device with which regmap construct is associated.
+ * @mux_node: mdio bus mux node that contains parent mdio bus phandle.
+ *	      This node also contains sub nodes, where each subnode denotes
+ *	      a child mdio bus. All the child mdio buses are muxed, i.e. at a
+ *	      time only one of the child mdio buses can be used.
+ * @data: to store the address of data allocated by this function
+ */
+int mdio_mux_regmap_init(struct device *dev,
+			 struct device_node *mux_node,
+			 void **data);
+
+/**
+ * mdio_mux_regmap_uninit - relinquish the control of MDIO bus muxing using
+ *			    regmap constructs.
+ * @data: address of data allocated by mdio_mux_regmap_init
+ */
+int mdio_mux_regmap_uninit(void *data);
+
 #endif /* __LINUX_MDIO_MUX_H */
-- 
2.17.1