drivers/net/mdio/mdio-mux-multiplexer.c

   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");