text: // SPDX-License-Identifier: GPL-2.0
  /*
   * Simple memory-mapped device MDIO MUX driver
   *
   * Author: Timur Tabi <timur@freescale.com>
   *
   * Copyright 2012 Freescale Semiconductor, Inc.
   */
  
  #include <linux/platform_device.h>
  #include <linux/device.h>
  #include <linux/of_address.h>
  #include <linux/of_mdio.h>
  #include <linux/module.h>
  #include <linux/phy.h>
  #include <linux/mdio-mux.h>
  
  struct mdio_mux_mmioreg_state {
  	void *mux_handle;
  	phys_addr_t phys;
  	unsigned int iosize;
  	unsigned int mask;
  };
  
  /*
   * MDIO multiplexing switch function
   *
   * This function is called by the mdio-mux layer when it thinks the mdio bus
   * multiplexer needs to switch.
   *
   * 'current_child' is the current value of the mux register (masked via
   * s->mask).
   *
   * 'desired_child' is the value of the 'reg' property of the target child MDIO
   * node.
   *
   * The first time this function is called, current_child == -1.
   *
   * If current_child == desired_child, then the mux is already set to the
   * correct bus.
   */
  static int mdio_mux_mmioreg_switch_fn(int current_child, int desired_child,
  				      void *data)
  {
  	struct mdio_mux_mmioreg_state *s = data;
  
  	if (current_child ^ desired_child) {
  		void __iomem *p = ioremap(s->phys, s->iosize);
  		if (!p)
  			return -ENOMEM;
  
  		switch (s->iosize) {
  		case sizeof(uint8_t): {
  			uint8_t x, y;
  
  			x = ioread8(p);
  			y = (x & ~s->mask) | desired_child;
  			if (x != y) {
  				iowrite8((x & ~s->mask) | desired_child, p);
  				pr_debug("%s: %02x -> %02x\n", __func__, x, y);
  			}
  
  			break;
  		}
  		case sizeof(uint16_t): {
  			uint16_t x, y;
  
  			x = ioread16(p);
  			y = (x & ~s->mask) | desired_child;
  			if (x != y) {
  				iowrite16((x & ~s->mask) | desired_child, p);
  				pr_debug("%s: %04x -> %04x\n", __func__, x, y);
  			}
  
  			break;
  		}
  		case sizeof(uint32_t): {
  			uint32_t x, y;
  
  			x = ioread32(p);
  			y = (x & ~s->mask) | desired_child;
  			if (x != y) {
  				iowrite32((x & ~s->mask) | desired_child, p);
  				pr_debug("%s: %08x -> %08x\n", __func__, x, y);
  			}
  
  			break;
  		}
  		}
  
  		iounmap(p);
  	}
  
  	return 0;
  }
  
  static int mdio_mux_mmioreg_probe(struct platform_device *pdev)
  {
  	struct device_node *np2, *np = pdev->dev.of_node;
  	struct mdio_mux_mmioreg_state *s;
  	struct resource res;
  	const __be32 *iprop;
  	int len, ret;
  
  	dev_dbg(&pdev->dev, "probing node %pOF\n", np);
  
  	s = devm_kzalloc(&pdev->dev, sizeof(*s), GFP_KERNEL);
  	if (!s)
  		return -ENOMEM;
  
  	ret = of_address_to_resource(np, 0, &res);
  	if (ret) {
  		dev_err(&pdev->dev, "could not obtain memory map for node %pOF\n",
  			np);
  		return ret;
  	}
  	s->phys = res.start;
  
  	s->iosize = resource_size(&res);
  	if (s->iosize != sizeof(uint8_t) &&
  	    s->iosize != sizeof(uint16_t) &&
  	    s->iosize != sizeof(uint32_t)) {
  		dev_err(&pdev->dev, "only 8/16/32-bit registers are supported\n");
  		return -EINVAL;
  	}
  
  	iprop = of_get_property(np, "mux-mask", &len);
  	if (!iprop || len != sizeof(uint32_t)) {
  		dev_err(&pdev->dev, "missing or invalid mux-mask property\n");
  		return -ENODEV;
  	}
  	if (be32_to_cpup(iprop) >= BIT(s->iosize * 8)) {
  		dev_err(&pdev->dev, "only 8/16/32-bit registers are supported\n");
  		return -EINVAL;
  	}
  	s->mask = be32_to_cpup(iprop);
  
  	/*
  	 * Verify that the 'reg' property of each child MDIO bus does not
  	 * set any bits outside of the 'mask'.
  	 */
  	for_each_available_child_of_node(np, np2) {
  		iprop = of_get_property(np2, "reg", &len);
  		if (!iprop || len != sizeof(uint32_t)) {
  			dev_err(&pdev->dev, "mdio-mux child node %pOF is "
  				"missing a 'reg' property\n", np2);
  			of_node_put(np2);
  			return -ENODEV;
  		}
  		if (be32_to_cpup(iprop) & ~s->mask) {
  			dev_err(&pdev->dev, "mdio-mux child node %pOF has "
  				"a 'reg' value with unmasked bits\n",
  				np2);
  			of_node_put(np2);
  			return -ENODEV;
  		}
  	}
  
  	ret = mdio_mux_init(&pdev->dev, pdev->dev.of_node,
  			    mdio_mux_mmioreg_switch_fn,
  			    &s->mux_handle, s, NULL);
  	if (ret) {
  		if (ret != -EPROBE_DEFER)
  			dev_err(&pdev->dev,
  				"failed to register mdio-mux bus %pOF\n", np);
  		return ret;
  	}
  
  	pdev->dev.platform_data = s;
  
  	return 0;
  }
  
  static int mdio_mux_mmioreg_remove(struct platform_device *pdev)
  {
  	struct mdio_mux_mmioreg_state *s = dev_get_platdata(&pdev->dev);
  
  	mdio_mux_uninit(s->mux_handle);
  
  	return 0;
  }
  
  static const struct of_device_id mdio_mux_mmioreg_match[] = {
  	{
  		.compatible = "mdio-mux-mmioreg",
  	},
  	{},
  };
  MODULE_DEVICE_TABLE(of, mdio_mux_mmioreg_match);
  
  static struct platform_driver mdio_mux_mmioreg_driver = {
  	.driver = {
  		.name		= "mdio-mux-mmioreg",
  		.of_match_table = mdio_mux_mmioreg_match,
  	},
  	.probe		= mdio_mux_mmioreg_probe,
  	.remove		= mdio_mux_mmioreg_remove,
  };
  
  module_platform_driver(mdio_mux_mmioreg_driver);
  
  MODULE_AUTHOR("Timur Tabi <timur@freescale.com>");
  MODULE_DESCRIPTION("Memory-mapped device MDIO MUX driver");
  MODULE_LICENSE("GPL v2");
  