netdev/phy: add MDIO bus multiplexer driven by a memory-mapped device

Add support for an MDIO bus multiplexer controlled by a simple memory-mapped
device, like an FPGA.  The device must be memory-mapped and contain only
8-bit registers (which keeps things simple).

Tested on a Freescale P5020DS board which uses the "PIXIS" FPGA attached
to the localbus.

Signed-off-by: Timur Tabi <timur@freescale.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 170 insertions, 0 deletions

diff --git a/drivers/net/phy/mdio-mux-mmioreg.c b/drivers/net/phy/mdio-mux-mmioreg.c
new file mode 100644
index 000000000000..098239a98b19
--- /dev/null
+++ b/drivers/net/phy/mdio-mux-mmioreg.c
@@ -0,0 +1,170 @@
+/*
+ * Simple memory-mapped device MDIO MUX driver
+ *
+ * Author: Timur Tabi <timur@freescale.com>
+ *
+ * Copyright 2012 Freescale Semiconductor, Inc.
+ *
+ * This file is licensed under the terms of the GNU General Public License
+ * version 2.  This program is licensed "as is" without any warranty of any
+ * kind, whether express or implied.
+ */
+
+#include <linux/platform_device.h>
+#include <linux/device.h>
+#include <linux/of_mdio.h>
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/phy.h>
+#include <linux/mdio-mux.h>
+
+struct mdio_mux_mmioreg_state {
+        void *mux_handle;
+        phys_addr_t phys;
+        uint8_t 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_mmioreg_switch_fn(int current_child, int desired_child,
+                                      void *data)
+{
+        struct mdio_mux_mmioreg_state *s = data;
+
+        if (current_child ^ desired_child) {
+                void *p = ioremap(s->phys, 1);
+                uint8_t x, y;
+
+                if (!p)
+                        return -ENOMEM;
+
+                x = ioread8(p);
+                y = (x & ~s->mask) | desired_child;
+                if (x != y) {
+                        iowrite8((x & ~s->mask) | desired_child, p);
+                        pr_debug("%s: %02x -> %02x\n", __func__, x, y);
+                }
+
+                iounmap(p);
+        }
+
+        return 0;
+}
+
+static int __devinit mdio_mux_mmioreg_probe(struct platform_device *pdev)
+{
+        struct device_node *np2, *np = pdev->dev.of_node;
+        struct mdio_mux_mmioreg_state *s;
+        struct resource res;
+        const __be32 *iprop;
+        int len, ret;
+
+        dev_dbg(&pdev->dev, "probing node %s\n", np->full_name);
+
+        s = devm_kzalloc(&pdev->dev, sizeof(*s), GFP_KERNEL);
+        if (!s)
+                return -ENOMEM;
+
+        ret = of_address_to_resource(np, 0, &res);
+        if (ret) {
+                dev_err(&pdev->dev, "could not obtain memory map for node %s\n",
+                        np->full_name);
+                return ret;
+        }
+        s->phys = res.start;
+
+        if (resource_size(&res) != sizeof(uint8_t)) {
+                dev_err(&pdev->dev, "only 8-bit registers are supported\n");
+                return -EINVAL;
+        }
+
+        iprop = of_get_property(np, "mux-mask", &len);
+        if (!iprop || len != sizeof(uint32_t)) {
+                dev_err(&pdev->dev, "missing or invalid mux-mask property\n");
+                return -ENODEV;
+        }
+        if (be32_to_cpup(iprop) > 255) {
+                dev_err(&pdev->dev, "only 8-bit registers are supported\n");
+                return -EINVAL;
+        }
+        s->mask = be32_to_cpup(iprop);
+
+        /*
+         * 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) {
+                iprop = of_get_property(np2, "reg", &len);
+                if (!iprop || len != sizeof(uint32_t)) {
+                        dev_err(&pdev->dev, "mdio-mux child node %s is "
+                                "missing a 'reg' property\n", np2->full_name);
+                        return -ENODEV;
+                }
+                if (be32_to_cpup(iprop) & ~s->mask) {
+                        dev_err(&pdev->dev, "mdio-mux child node %s has "
+                                "a 'reg' value with unmasked bits\n",
+                                np2->full_name);
+                        return -ENODEV;
+                }
+        }
+
+        ret = mdio_mux_init(&pdev->dev, mdio_mux_mmioreg_switch_fn,
+                            &s->mux_handle, s);
+        if (ret) {
+                dev_err(&pdev->dev, "failed to register mdio-mux bus %s\n",
+                        np->full_name);
+                return ret;
+        }
+
+        pdev->dev.platform_data = s;
+
+        return 0;
+}
+
+static int __devexit mdio_mux_mmioreg_remove(struct platform_device *pdev)
+{
+        struct mdio_mux_mmioreg_state *s = dev_get_platdata(&pdev->dev);
+
+        mdio_mux_uninit(s->mux_handle);
+
+        return 0;
+}
+
+static struct of_device_id mdio_mux_mmioreg_match[] = {
+        {
+                .compatible = "mdio-mux-mmioreg",
+        },
+        {},
+};
+MODULE_DEVICE_TABLE(of, mdio_mux_mmioreg_match);
+
+static struct platform_driver mdio_mux_mmioreg_driver = {
+        .driver = {
+                .name           = "mdio-mux-mmioreg",
+                .owner          = THIS_MODULE,
+                .of_match_table = mdio_mux_mmioreg_match,
+        },
+        .probe          = mdio_mux_mmioreg_probe,
+        .remove         = __devexit_p(mdio_mux_mmioreg_remove),
+};
+
+module_platform_driver(mdio_mux_mmioreg_driver);
+
+MODULE_AUTHOR("Timur Tabi <timur@freescale.com>");
+MODULE_DESCRIPTION("Memory-mapped device MDIO MUX driver");
+MODULE_LICENSE("GPL v2");