// SPDX-License-Identifier: GPL-2.0-or-later

  /*
   *	sc520_freq.c: cpufreq driver for the AMD Elan sc520
   *
   *	Copyright (C) 2005 Sean Young <sean@mess.org>
   *

   *	Based on elanfreq.c
   *
   *	2005-03-30: - initial revision
   */

  #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

  #include <linux/kernel.h>
  #include <linux/module.h>
  #include <linux/init.h>
  
  #include <linux/delay.h>
  #include <linux/cpufreq.h>

  #include <linux/timex.h>
  #include <linux/io.h>

  #include <asm/cpu_device_id.h>

  #include <asm/msr.h>

  
  #define MMCR_BASE	0xfffef000	/* The default base address */
  #define OFFS_CPUCTL	0x2   /* CPU Control Register */
  
  static __u8 __iomem *cpuctl;

  static struct cpufreq_frequency_table sc520_freq_table[] = {

  	{0, 0x01,	100000},
  	{0, 0x02,	133000},
  	{0, 0,	CPUFREQ_TABLE_END},

  };
  
  static unsigned int sc520_freq_get_cpu_frequency(unsigned int cpu)
  {
  	u8 clockspeed_reg = *cpuctl;
  
  	switch (clockspeed_reg & 0x03) {
  	default:

  		pr_err("error: cpuctl register has unexpected value %02x
  ",

  		       clockspeed_reg);

  	case 0x01:
  		return 100000;
  	case 0x02:
  		return 133000;
  	}
  }

  static int sc520_freq_target(struct cpufreq_policy *policy, unsigned int state)

  {

  	u8 clockspeed_reg;

  	local_irq_disable();
  
  	clockspeed_reg = *cpuctl & ~0x03;

  	*cpuctl = clockspeed_reg | sc520_freq_table[state].driver_data;

  
  	local_irq_enable();

  	return 0;
  }

  /*
   *	Module init and exit code
   */
  
  static int sc520_freq_cpu_init(struct cpufreq_policy *policy)
  {

  	struct cpuinfo_x86 *c = &cpu_data(0);

  
  	/* capability check */
  	if (c->x86_vendor != X86_VENDOR_AMD ||
  	    c->x86 != 4 || c->x86_model != 9)
  		return -ENODEV;
  
  	/* cpuinfo and default policy values */

  	policy->cpuinfo.transition_latency = 1000000; /* 1ms */

  	policy->freq_table = sc520_freq_table;

  	return 0;

  }

  static struct cpufreq_driver sc520_freq_driver = {

  	.get	= sc520_freq_get_cpu_frequency,

  	.verify	= cpufreq_generic_frequency_table_verify,

  	.target_index = sc520_freq_target,

  	.init	= sc520_freq_cpu_init,

  	.name	= "sc520_freq",

  	.attr	= cpufreq_generic_attr,

  };

  static const struct x86_cpu_id sc520_ids[] = {

  	X86_MATCH_VENDOR_FAM_MODEL(AMD, 4, 9, NULL),

  	{}
  };
  MODULE_DEVICE_TABLE(x86cpu, sc520_ids);

  
  static int __init sc520_freq_init(void)
  {

  	int err;

  	if (!x86_match_cpu(sc520_ids))

  		return -ENODEV;

  	cpuctl = ioremap((unsigned long)(MMCR_BASE + OFFS_CPUCTL), 1);

  	if (!cpuctl) {

  		pr_err("sc520_freq: error: failed to remap memory
  ");

  		return -ENOMEM;
  	}

  	err = cpufreq_register_driver(&sc520_freq_driver);
  	if (err)
  		iounmap(cpuctl);
  
  	return err;

  }
  
  
  static void __exit sc520_freq_exit(void)
  {
  	cpufreq_unregister_driver(&sc520_freq_driver);
  	iounmap(cpuctl);
  }
  
  
  MODULE_LICENSE("GPL");
  MODULE_AUTHOR("Sean Young <sean@mess.org>");
  MODULE_DESCRIPTION("cpufreq driver for AMD's Elan sc520 CPU");
  
  module_init(sc520_freq_init);
  module_exit(sc520_freq_exit);