/*
   *	sc520_freq.c: cpufreq driver for the AMD Elan sc520
   *
   *	Copyright (C) 2005 Sean Young <sean@mess.org>
   *
   *	This program is free software; you can redistribute it and/or
   *	modify it under the terms of the GNU General Public License
   *	as published by the Free Software Foundation; either version
   *	2 of the License, or (at your option) any later version.
   *
   *	Based on elanfreq.c
   *
   *	2005-03-30: - initial revision
   */
  
  #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/msr.h>

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

  #define PFX "sc520_freq: "

  
  static struct cpufreq_frequency_table sc520_freq_table[] = {
  	{0x01,	100000},
  	{0x02,	133000},
  	{0,	CPUFREQ_TABLE_END},
  };
  
  static unsigned int sc520_freq_get_cpu_frequency(unsigned int cpu)
  {
  	u8 clockspeed_reg = *cpuctl;
  
  	switch (clockspeed_reg & 0x03) {
  	default:

  		printk(KERN_ERR PFX "error: cpuctl register has unexpected "
  				"value %02x
  ", clockspeed_reg);

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

  static void sc520_freq_set_cpu_state(unsigned int state)

  {
  
  	struct cpufreq_freqs	freqs;
  	u8 clockspeed_reg;
  
  	freqs.old = sc520_freq_get_cpu_frequency(0);
  	freqs.new = sc520_freq_table[state].frequency;
  	freqs.cpu = 0; /* AMD Elan is UP */
  
  	cpufreq_notify_transition(&freqs, CPUFREQ_PRECHANGE);

  	pr_debug("attempting to set frequency to %i kHz
  ",

  			sc520_freq_table[state].frequency);
  
  	local_irq_disable();
  
  	clockspeed_reg = *cpuctl & ~0x03;
  	*cpuctl = clockspeed_reg | sc520_freq_table[state].index;
  
  	local_irq_enable();
  
  	cpufreq_notify_transition(&freqs, CPUFREQ_POSTCHANGE);
  };

  static int sc520_freq_verify(struct cpufreq_policy *policy)

  {
  	return cpufreq_frequency_table_verify(policy, &sc520_freq_table[0]);
  }

  static int sc520_freq_target(struct cpufreq_policy *policy,

  			    unsigned int target_freq,
  			    unsigned int relation)
  {
  	unsigned int newstate = 0;

  	if (cpufreq_frequency_table_target(policy, sc520_freq_table,
  				target_freq, relation, &newstate))

  		return -EINVAL;
  
  	sc520_freq_set_cpu_state(newstate);
  
  	return 0;
  }
  
  
  /*
   *	Module init and exit code
   */
  
  static int sc520_freq_cpu_init(struct cpufreq_policy *policy)
  {

  	struct cpuinfo_x86 *c = &cpu_data(0);

  	int result;
  
  	/* 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->cur = sc520_freq_get_cpu_frequency(0);
  
  	result = cpufreq_frequency_table_cpuinfo(policy, sc520_freq_table);
  	if (result)

  		return result;

  
  	cpufreq_frequency_table_get_attr(sc520_freq_table, policy->cpu);
  
  	return 0;
  }
  
  
  static int sc520_freq_cpu_exit(struct cpufreq_policy *policy)
  {
  	cpufreq_frequency_table_put_attr(policy->cpu);
  	return 0;
  }

  static struct freq_attr *sc520_freq_attr[] = {

  	&cpufreq_freq_attr_scaling_available_freqs,
  	NULL,
  };

  static struct cpufreq_driver sc520_freq_driver = {

  	.get	= sc520_freq_get_cpu_frequency,
  	.verify	= sc520_freq_verify,
  	.target	= sc520_freq_target,
  	.init	= sc520_freq_cpu_init,
  	.exit	= sc520_freq_cpu_exit,
  	.name	= "sc520_freq",
  	.owner	= THIS_MODULE,
  	.attr	= sc520_freq_attr,
  };
  
  
  static int __init sc520_freq_init(void)
  {

  	struct cpuinfo_x86 *c = &cpu_data(0);

  	int err;

  
  	/* Test if we have the right hardware */

  	if (c->x86_vendor != X86_VENDOR_AMD ||
  	    c->x86 != 4 || c->x86_model != 9) {

  		pr_debug("no Elan SC520 processor found!
  ");

  		return -ENODEV;
  	}
  	cpuctl = ioremap((unsigned long)(MMCR_BASE + OFFS_CPUCTL), 1);

  	if (!cpuctl) {

  		printk(KERN_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);