Date:   Sun,  7 Oct 2018 23:54:23 +0530
From:   Pankaj Bansal <pankaj.bansal@....com>
To:     Andrew Lunn <andrew@...n.ch>,
        Florian Fainelli <f.fainelli@...il.com>
Cc:     netdev@...r.kernel.org, Pankaj Bansal <pankaj.bansal@....com>
Subject: [PATCH v2 2/2] netdev/phy: add MDIO bus multiplexer driven by a regmap

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@....com>
---

Notes:
    V2:
     - replaced be32_to_cpup with of_property_read_u32
     - incorporated Andrew's comments

 drivers/net/phy/Kconfig           |  13 +++
 drivers/net/phy/Makefile          |   1 +
 drivers/net/phy/mdio-mux-regmap.c | 171 ++++++++++++++++++++++++++++
 3 files changed, 185 insertions(+)

diff --git a/drivers/net/phy/Kconfig b/drivers/net/phy/Kconfig
index 82070792edbb..d1ac9e70cbb2 100644
--- a/drivers/net/phy/Kconfig
+++ b/drivers/net/phy/Kconfig
@@ -87,6 +87,19 @@ config MDIO_BUS_MUX_MMIOREG
 
 	  Currently, only 8/16/32 bits registers are supported.
 
+config MDIO_BUS_MUX_REGMAP
+	tristate "REGMAP controlled MDIO bus multiplexers"
+	depends on OF_MDIO && REGMAP
+	select MDIO_BUS_MUX
+	help
+	  This module provides a driver for MDIO bus multiplexers that
+	  are controlled via a regmap device, like an FPGA connected to i2c.
+	  The multiplexer connects one of several child MDIO busses to a
+	  parent bus.Child bus selection is under the control of one of
+	  the FPGA's registers.
+
+	  Currently, only upto 32 bits registers are supported.
+
 config MDIO_CAVIUM
 	tristate
 
diff --git a/drivers/net/phy/Makefile b/drivers/net/phy/Makefile
index 5805c0b7d60e..33053f9f320d 100644
--- a/drivers/net/phy/Makefile
+++ b/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-$(CONFIG_MDIO_BUS_MUX_REGMAP) += mdio-mux-regmap.o
 obj-$(CONFIG_MDIO_CAVIUM)	+= mdio-cavium.o
 obj-$(CONFIG_MDIO_GPIO)		+= mdio-gpio.o
 obj-$(CONFIG_MDIO_HISI_FEMAC)	+= mdio-hisi-femac.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..6068d05a728a
--- /dev/null
+++ b/drivers/net/phy/mdio-mux-regmap.c
@@ -0,0 +1,171 @@
+// 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.bansal@....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 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)
+		pr_debug("%s %d -> %d\n", __func__, current_child,
+			 desired_child);
+	return ret;
+}
+
+static int mdio_mux_regmap_probe(struct platform_device *pdev)
+{
+	struct device_node *np2, *np = pdev->dev.of_node;
+	struct mdio_mux_regmap_state *s;
+	int ret;
+	u32 val;
+
+	dev_dbg(&pdev->dev, "probing node %pOF\n", np);
+
+	s = devm_kzalloc(&pdev->dev, sizeof(*s), GFP_KERNEL);
+	if (!s)
+		return -ENOMEM;
+
+	s->regmap = dev_get_regmap(pdev->dev.parent, NULL);
+	if (IS_ERR(s->regmap)) {
+		dev_err(&pdev->dev, "Failed to get parent regmap\n");
+		return PTR_ERR(s->regmap);
+	}
+
+	ret = of_property_read_u32(np, "reg", &s->mux_reg);
+	if (ret) {
+		dev_err(&pdev->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(&pdev->dev, "error while reading reg\n");
+		return ret;
+	}
+
+	ret = regmap_write(s->regmap, s->mux_reg, val);
+	if (ret) {
+		dev_err(&pdev->dev, "error while writing reg\n");
+		return ret;
+	}
+
+	ret = of_property_read_u32(np, "mux-mask", &s->mask);
+	if (ret) {
+		dev_err(&pdev->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(np, np2) {
+		ret = of_property_read_u32(np2, "reg", &val);
+		if (ret) {
+			dev_err(&pdev->dev, "mdio-mux child node %pOF is missing a 'reg' property\n", np2);
+			of_node_put(np2);
+			return -ENODEV;
+		}
+		if (val & ~s->mask) {
+			dev_err(&pdev->dev, "mdio-mux child node %pOF has a 'reg' value with unmasked bits\n", np2);
+			of_node_put(np2);
+			return -ENODEV;
+		}
+	}
+
+	ret = mdio_mux_init(&pdev->dev, pdev->dev.of_node,
+			    mdio_mux_regmap_switch_fn,
+			    &s->mux_handle, s, NULL);
+	if (ret) {
+		if (ret != -EPROBE_DEFER)
+			dev_err(&pdev->dev,
+				"failed to register mdio-mux bus %pOF\n", np);
+		return ret;
+	}
+
+	pdev->dev.platform_data = s;
+
+	return 0;
+}
+
+static int mdio_mux_regmap_remove(struct platform_device *pdev)
+{
+	struct mdio_mux_regmap_state *s = dev_get_platdata(&pdev->dev);
+
+	mdio_mux_uninit(s->mux_handle);
+
+	return 0;
+}
+
+static const struct of_device_id mdio_mux_regmap_match[] = {
+	{
+		.compatible = "mdio-mux-regmap",
+	},
+	{},
+};
+MODULE_DEVICE_TABLE(of, mdio_mux_regmap_match);
+
+static struct platform_driver mdio_mux_regmap_driver = {
+	.driver = {
+		.name		= "mdio-mux-regmap",
+		.of_match_table = mdio_mux_regmap_match,
+	},
+	.probe		= mdio_mux_regmap_probe,
+	.remove		= mdio_mux_regmap_remove,
+};
+
+module_platform_driver(mdio_mux_regmap_driver);
+
+MODULE_AUTHOR("Pankaj Bansal <pankaj.bansal@....com>");
+MODULE_DESCRIPTION("regmap device MDIO MUX driver");
+MODULE_LICENSE("GPL v2");
-- 
2.17.1

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