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		return dev_err_probe(&pdev->dev, PTR_ERR(s->muxc),
77				     "Failed to get mux\n");
78
79	platform_set_drvdata(pdev, s);
80
81	ret = mdio_mux_init(&pdev->dev, pdev->dev.of_node,
82			    mdio_mux_multiplexer_switch_fn, &s->mux_handle,
83			    pdev, NULL);
84
85	return ret;
86}
87
88static void mdio_mux_multiplexer_remove(struct platform_device *pdev)
89{
90	struct mdio_mux_multiplexer_state *s = platform_get_drvdata(pdev);
91
92	mdio_mux_uninit(s->mux_handle);
93
94	if (s->do_deselect)
95		mux_control_deselect(s->muxc);
96}
97
98static const struct of_device_id mdio_mux_multiplexer_match[] = {
99	{ .compatible = "mdio-mux-multiplexer", },
100	{},
101};
102MODULE_DEVICE_TABLE(of, mdio_mux_multiplexer_match);
103
104static struct platform_driver mdio_mux_multiplexer_driver = {
105	.driver = {
106		.name		= "mdio-mux-multiplexer",
107		.of_match_table	= mdio_mux_multiplexer_match,
108	},
109	.probe		= mdio_mux_multiplexer_probe,
110	.remove_new	= mdio_mux_multiplexer_remove,
111};
112
113module_platform_driver(mdio_mux_multiplexer_driver);
114
115MODULE_DESCRIPTION("MDIO bus multiplexer using kernel multiplexer subsystem");
116MODULE_AUTHOR("Pankaj Bansal <pankaj.bansal@nxp.com>");
117MODULE_LICENSE("GPL");
118