net/mdio/mdio-mux-multiplexer.c

0001 // SPDX-License-Identifier: GPL-2.0+
0002 /* MDIO bus multiplexer using kernel multiplexer subsystem
0003  *
0004  * Copyright 2019 NXP
0005  */
0006
0007 #include <linux/mdio-mux.h>
0008 #include <linux/module.h>
0009 #include <linux/mux/consumer.h>
0010 #include <linux/platform_device.h>
0011
0012 struct mdio_mux_multiplexer_state {
0013     struct mux_control *muxc;
0014     bool do_deselect;
0015     void *mux_handle;
0016 };
0017
0018 /**
0019  * mdio_mux_multiplexer_switch_fn - This function is called by the mdio-mux
0020  *                                  layer when it thinks the mdio bus
0021  *                                  multiplexer needs to switch.
0022  * @current_child:  current value of the mux register.
0023  * @desired_child: value of the 'reg' property of the target child MDIO node.
0024  * @data: Private data used by this switch_fn passed to mdio_mux_init function
0025  *        via mdio_mux_init(.., .., .., .., data, ..).
0026  *
0027  * The first time this function is called, current_child == -1.
0028  * If current_child == desired_child, then the mux is already set to the
0029  * correct bus.
0030  */
0031 static int mdio_mux_multiplexer_switch_fn(int current_child, int desired_child,
0032                       void *data)
0033 {
0034     struct platform_device *pdev;
0035     struct mdio_mux_multiplexer_state *s;
0036     int ret = 0;
0037
0038     pdev = (struct platform_device *)data;
0039     s = platform_get_drvdata(pdev);
0040
0041     if (!(current_child ^ desired_child))
0042         return 0;
0043
0044     if (s->do_deselect)
0045         ret = mux_control_deselect(s->muxc);
0046     if (ret) {
0047         dev_err(&pdev->dev, "mux_control_deselect failed in %s: %d\n",
0048             __func__, ret);
0049         return ret;
0050     }
0051
0052     ret =  mux_control_select(s->muxc, desired_child);
0053     if (!ret) {
0054         dev_dbg(&pdev->dev, "%s %d -> %d\n", __func__, current_child,
0055             desired_child);
0056         s->do_deselect = true;
0057     } else {
0058         s->do_deselect = false;
0059     }
0060
0061     return ret;
0062 }
0063
0064 static int mdio_mux_multiplexer_probe(struct platform_device *pdev)
0065 {
0066     struct device *dev = &pdev->dev;
0067     struct mdio_mux_multiplexer_state *s;
0068     int ret = 0;
0069
0070     s = devm_kzalloc(&pdev->dev, sizeof(*s), GFP_KERNEL);
0071     if (!s)
0072         return -ENOMEM;
0073
0074     s->muxc = devm_mux_control_get(dev, NULL);
0075     if (IS_ERR(s->muxc)) {
0076         ret = PTR_ERR(s->muxc);
0077         if (ret != -EPROBE_DEFER)
0078             dev_err(&pdev->dev, "Failed to get mux: %d\n", ret);
0079         return ret;
0080     }
0081
0082     platform_set_drvdata(pdev, s);
0083
0084     ret = mdio_mux_init(&pdev->dev, pdev->dev.of_node,
0085                 mdio_mux_multiplexer_switch_fn, &s->mux_handle,
0086                 pdev, NULL);
0087
0088     return ret;
0089 }
0090
0091 static int mdio_mux_multiplexer_remove(struct platform_device *pdev)
0092 {
0093     struct mdio_mux_multiplexer_state *s = platform_get_drvdata(pdev);
0094
0095     mdio_mux_uninit(s->mux_handle);
0096
0097     if (s->do_deselect)
0098         mux_control_deselect(s->muxc);
0099
0100     return 0;
0101 }
0102
0103 static const struct of_device_id mdio_mux_multiplexer_match[] = {
0104     { .compatible = "mdio-mux-multiplexer", },
0105     {},
0106 };
0107 MODULE_DEVICE_TABLE(of, mdio_mux_multiplexer_match);
0108
0109 static struct platform_driver mdio_mux_multiplexer_driver = {
0110     .driver = {
0111         .name       = "mdio-mux-multiplexer",
0112         .of_match_table = mdio_mux_multiplexer_match,
0113     },
0114     .probe      = mdio_mux_multiplexer_probe,
0115     .remove     = mdio_mux_multiplexer_remove,
0116 };
0117
0118 module_platform_driver(mdio_mux_multiplexer_driver);
0119
0120 MODULE_DESCRIPTION("MDIO bus multiplexer using kernel multiplexer subsystem");
0121 MODULE_AUTHOR("Pankaj Bansal <pankaj.bansal@nxp.com>");
0122 MODULE_LICENSE("GPL");