1/*
  2 * Simple memory-mapped device MDIO MUX driver
  3 *
  4 * Author: Timur Tabi <timur@freescale.com>
  5 *
  6 * Copyright 2012 Freescale Semiconductor, Inc.
  7 *
  8 * This file is licensed under the terms of the GNU General Public License
  9 * version 2.  This program is licensed "as is" without any warranty of any
 10 * kind, whether express or implied.
 11 */
 12
 13#include <linux/platform_device.h>
 14#include <linux/device.h>
 15#include <linux/of_address.h>
 16#include <linux/of_mdio.h>
 17#include <linux/module.h>
 18#include <linux/phy.h>
 19#include <linux/mdio-mux.h>
 20
 21struct mdio_mux_mmioreg_state {
 22	void *mux_handle;
 23	phys_addr_t phys;
 24	uint8_t mask;
 25};
 26
 27/*
 28 * MDIO multiplexing switch function
 29 *
 30 * This function is called by the mdio-mux layer when it thinks the mdio bus
 31 * multiplexer needs to switch.
 32 *
 33 * 'current_child' is the current value of the mux register (masked via
 34 * s->mask).
 35 *
 36 * 'desired_child' is the value of the 'reg' property of the target child MDIO
 37 * node.
 38 *
 39 * The first time this function is called, current_child == -1.
 40 *
 41 * If current_child == desired_child, then the mux is already set to the
 42 * correct bus.
 43 */
 44static int mdio_mux_mmioreg_switch_fn(int current_child, int desired_child,
 45				      void *data)
 46{
 47	struct mdio_mux_mmioreg_state *s = data;
 48
 49	if (current_child ^ desired_child) {
 50		void __iomem *p = ioremap(s->phys, 1);
 51		uint8_t x, y;
 52
 53		if (!p)
 54			return -ENOMEM;
 55
 56		x = ioread8(p);
 57		y = (x & ~s->mask) | desired_child;
 58		if (x != y) {
 59			iowrite8((x & ~s->mask) | desired_child, p);
 60			pr_debug("%s: %02x -> %02x\n", __func__, x, y);
 61		}
 62
 63		iounmap(p);
 64	}
 65
 66	return 0;
 67}
 68
 69static int mdio_mux_mmioreg_probe(struct platform_device *pdev)
 70{
 71	struct device_node *np2, *np = pdev->dev.of_node;
 72	struct mdio_mux_mmioreg_state *s;
 73	struct resource res;
 74	const __be32 *iprop;
 75	int len, ret;
 76
 77	dev_dbg(&pdev->dev, "probing node %s\n", np->full_name);
 78
 79	s = devm_kzalloc(&pdev->dev, sizeof(*s), GFP_KERNEL);
 80	if (!s)
 81		return -ENOMEM;
 82
 83	ret = of_address_to_resource(np, 0, &res);
 84	if (ret) {
 85		dev_err(&pdev->dev, "could not obtain memory map for node %s\n",
 86			np->full_name);
 87		return ret;
 88	}
 89	s->phys = res.start;
 90
 91	if (resource_size(&res) != sizeof(uint8_t)) {
 92		dev_err(&pdev->dev, "only 8-bit registers are supported\n");
 93		return -EINVAL;
 94	}
 95
 96	iprop = of_get_property(np, "mux-mask", &len);
 97	if (!iprop || len != sizeof(uint32_t)) {
 98		dev_err(&pdev->dev, "missing or invalid mux-mask property\n");
 99		return -ENODEV;
100	}
101	if (be32_to_cpup(iprop) > 255) {
102		dev_err(&pdev->dev, "only 8-bit registers are supported\n");
103		return -EINVAL;
104	}
105	s->mask = be32_to_cpup(iprop);
106
107	/*
108	 * Verify that the 'reg' property of each child MDIO bus does not
109	 * set any bits outside of the 'mask'.
110	 */
111	for_each_available_child_of_node(np, np2) {
112		iprop = of_get_property(np2, "reg", &len);
113		if (!iprop || len != sizeof(uint32_t)) {
114			dev_err(&pdev->dev, "mdio-mux child node %s is "
115				"missing a 'reg' property\n", np2->full_name);
116			return -ENODEV;
117		}
118		if (be32_to_cpup(iprop) & ~s->mask) {
119			dev_err(&pdev->dev, "mdio-mux child node %s has "
120				"a 'reg' value with unmasked bits\n",
121				np2->full_name);
122			return -ENODEV;
123		}
124	}
125
126	ret = mdio_mux_init(&pdev->dev, mdio_mux_mmioreg_switch_fn,
127			    &s->mux_handle, s);
128	if (ret) {
129		dev_err(&pdev->dev, "failed to register mdio-mux bus %s\n",
130			np->full_name);
131		return ret;
132	}
133
134	pdev->dev.platform_data = s;
135
136	return 0;
137}
138
139static int mdio_mux_mmioreg_remove(struct platform_device *pdev)
140{
141	struct mdio_mux_mmioreg_state *s = dev_get_platdata(&pdev->dev);
142
143	mdio_mux_uninit(s->mux_handle);
144
145	return 0;
146}
147
148static struct of_device_id mdio_mux_mmioreg_match[] = {
149	{
150		.compatible = "mdio-mux-mmioreg",
151	},
152	{},
153};
154MODULE_DEVICE_TABLE(of, mdio_mux_mmioreg_match);
155
156static struct platform_driver mdio_mux_mmioreg_driver = {
157	.driver = {
158		.name		= "mdio-mux-mmioreg",
159		.owner		= THIS_MODULE,
160		.of_match_table = mdio_mux_mmioreg_match,
161	},
162	.probe		= mdio_mux_mmioreg_probe,
163	.remove		= mdio_mux_mmioreg_remove,
164};
165
166module_platform_driver(mdio_mux_mmioreg_driver);
167
168MODULE_AUTHOR("Timur Tabi <timur@freescale.com>");
169MODULE_DESCRIPTION("Memory-mapped device MDIO MUX driver");
170MODULE_LICENSE("GPL v2");