text: // SPDX-License-Identifier: GPL-2.0
  
  /*
   * Memory Mapped IO Fixed clock driver
   *
   * Copyright (C) 2018 Cadence Design Systems, Inc.
   *
   * Authors:
   *	Jan Kotas <jank@cadence.com>
   */
  
  #include <linux/clk-provider.h>
  #include <linux/of_address.h>
  #include <linux/module.h>
  #include <linux/platform_device.h>
  
  static struct clk_hw *fixed_mmio_clk_setup(struct device_node *node)
  {
  	struct clk_hw *clk;
  	const char *clk_name = node->name;
  	void __iomem *base;
  	u32 freq;
  	int ret;
  
  	base = of_iomap(node, 0);
  	if (!base) {
  		pr_err("%pOFn: failed to map address\n", node);
  		return ERR_PTR(-EIO);
  	}
  
  	freq = readl(base);
  	iounmap(base);
  	of_property_read_string(node, "clock-output-names", &clk_name);
  
  	clk = clk_hw_register_fixed_rate(NULL, clk_name, NULL, 0, freq);
  	if (IS_ERR(clk)) {
  		pr_err("%pOFn: failed to register fixed rate clock\n", node);
  		return clk;
  	}
  
  	ret = of_clk_add_hw_provider(node, of_clk_hw_simple_get, clk);
  	if (ret) {
  		pr_err("%pOFn: failed to add clock provider\n", node);
  		clk_hw_unregister(clk);
  		clk = ERR_PTR(ret);
  	}
  
  	return clk;
  }
  
  static void __init of_fixed_mmio_clk_setup(struct device_node *node)
  {
  	fixed_mmio_clk_setup(node);
  }
  CLK_OF_DECLARE(fixed_mmio_clk, "fixed-mmio-clock", of_fixed_mmio_clk_setup);
  
  /**
   * This is not executed when of_fixed_mmio_clk_setup succeeded.
   */
  static int of_fixed_mmio_clk_probe(struct platform_device *pdev)
  {
  	struct clk_hw *clk;
  
  	clk = fixed_mmio_clk_setup(pdev->dev.of_node);
  	if (IS_ERR(clk))
  		return PTR_ERR(clk);
  
  	platform_set_drvdata(pdev, clk);
  
  	return 0;
  }
  
  static int of_fixed_mmio_clk_remove(struct platform_device *pdev)
  {
  	struct clk_hw *clk = platform_get_drvdata(pdev);
  
  	of_clk_del_provider(pdev->dev.of_node);
  	clk_hw_unregister_fixed_rate(clk);
  
  	return 0;
  }
  
  static const struct of_device_id of_fixed_mmio_clk_ids[] = {
  	{ .compatible = "fixed-mmio-clock" },
  	{ }
  };
  MODULE_DEVICE_TABLE(of, of_fixed_mmio_clk_ids);
  
  static struct platform_driver of_fixed_mmio_clk_driver = {
  	.driver = {
  		.name = "of_fixed_mmio_clk",
  		.of_match_table = of_fixed_mmio_clk_ids,
  	},
  	.probe = of_fixed_mmio_clk_probe,
  	.remove = of_fixed_mmio_clk_remove,
  };
  module_platform_driver(of_fixed_mmio_clk_driver);
  
  MODULE_AUTHOR("Jan Kotas <jank@cadence.com>");
  MODULE_DESCRIPTION("Memory Mapped IO Fixed clock driver");
  MODULE_LICENSE("GPL v2");
  