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 
12 struct 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  */
31 static 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 
64 static 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 
88 static int 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 	return 0;
98 }
99 
100 static const struct of_device_id mdio_mux_multiplexer_match[] = {
101 	{ .compatible = "mdio-mux-multiplexer", },
102 	{},
103 };
104 MODULE_DEVICE_TABLE(of, mdio_mux_multiplexer_match);
105 
106 static struct platform_driver mdio_mux_multiplexer_driver = {
107 	.driver = {
108 		.name		= "mdio-mux-multiplexer",
109 		.of_match_table	= mdio_mux_multiplexer_match,
110 	},
111 	.probe		= mdio_mux_multiplexer_probe,
112 	.remove		= mdio_mux_multiplexer_remove,
113 };
114 
115 module_platform_driver(mdio_mux_multiplexer_driver);
116 
117 MODULE_DESCRIPTION("MDIO bus multiplexer using kernel multiplexer subsystem");
118 MODULE_AUTHOR("Pankaj Bansal <pankaj.bansal@nxp.com>");
119 MODULE_LICENSE("GPL");
120