1// SPDX-License-Identifier: GPL-2.0+
2/* MDIO bus multiplexer using kernel multiplexer subsystem
3 *
4 * Copyright 2019 NXP
5 */
6
7#include <linux/mdio-mux.h>
8#include <linux/module.h>
9#include <linux/mux/consumer.h>
10#include <linux/platform_device.h>
11
12struct mdio_mux_multiplexer_state {
13	struct mux_control *muxc;
14	bool do_deselect;
15	void *mux_handle;
16};
17
18/**
19 * mdio_mux_multiplexer_switch_fn - This function is called by the mdio-mux
20 *                                  layer when it thinks the mdio bus
21 *                                  multiplexer needs to switch.
22 * @current_child:  current value of the mux register.
23 * @desired_child: value of the 'reg' property of the target child MDIO node.
24 * @data: Private data used by this switch_fn passed to mdio_mux_init function
25 *        via mdio_mux_init(.., .., .., .., data, ..).
26 *
27 * The first time this function is called, current_child == -1.
28 * If current_child == desired_child, then the mux is already set to the
29 * correct bus.
30 */
31static int mdio_mux_multiplexer_switch_fn(int current_child, int desired_child,
32					  void *data)
33{
34	struct platform_device *pdev;
35	struct mdio_mux_multiplexer_state *s;
36	int ret = 0;
37
38	pdev = (struct platform_device *)data;
39	s = platform_get_drvdata(pdev);
40
41	if (!(current_child ^ desired_child))
42		return 0;
43
44	if (s->do_deselect)
45		ret = mux_control_deselect(s->muxc);
46	if (ret) {
47		dev_err(&pdev->dev, "mux_control_deselect failed in %s: %d\n",
48			__func__, ret);
49		return ret;
50	}
51
52	ret =  mux_control_select(s->muxc, desired_child);
53	if (!ret) {
54		dev_dbg(&pdev->dev, "%s %d -> %d\n", __func__, current_child,
55			desired_child);
56		s->do_deselect = true;
57	} else {
58		s->do_deselect = false;
59	}
60
61	return ret;
62}
63
64static int mdio_mux_multiplexer_probe(struct platform_device *pdev)
65{
66	struct device *dev = &pdev->dev;
67	struct mdio_mux_multiplexer_state *s;
68	int ret = 0;
69
70	s = devm_kzalloc(&pdev->dev, sizeof(*s), GFP_KERNEL);
71	if (!s)
72		return -ENOMEM;
73
74	s->muxc = devm_mux_control_get(dev, NULL);
75	if (IS_ERR(s->muxc)) {
76		ret = PTR_ERR(s->muxc);
77		if (ret != -EPROBE_DEFER)
78			dev_err(&pdev->dev, "Failed to get mux: %d\n", ret);
79		return ret;
80	}
81
82	platform_set_drvdata(pdev, s);
83
84	ret = mdio_mux_init(&pdev->dev, pdev->dev.of_node,
85			    mdio_mux_multiplexer_switch_fn, &s->mux_handle,
86			    pdev, NULL);
87
88	return ret;
89}
90
91static int mdio_mux_multiplexer_remove(struct platform_device *pdev)
92{
93	struct mdio_mux_multiplexer_state *s = platform_get_drvdata(pdev);
94
95	mdio_mux_uninit(s->mux_handle);
96
97	if (s->do_deselect)
98		mux_control_deselect(s->muxc);
99
100	return 0;
101}
102
103static const struct of_device_id mdio_mux_multiplexer_match[] = {
104	{ .compatible = "mdio-mux-multiplexer", },
105	{},
106};
107MODULE_DEVICE_TABLE(of, mdio_mux_multiplexer_match);
108
109static struct platform_driver mdio_mux_multiplexer_driver = {
110	.driver = {
111		.name		= "mdio-mux-multiplexer",
112		.of_match_table	= mdio_mux_multiplexer_match,
113	},
114	.probe		= mdio_mux_multiplexer_probe,
115	.remove		= mdio_mux_multiplexer_remove,
116};
117
118module_platform_driver(mdio_mux_multiplexer_driver);
119
120MODULE_DESCRIPTION("MDIO bus multiplexer using kernel multiplexer subsystem");
121MODULE_AUTHOR("Pankaj Bansal <pankaj.bansal@nxp.com>");
122MODULE_LICENSE("GPL");
123