/*
   *  This file was based upon code in Powertweak Linux (http://powertweak.sf.net)

   *  (C) 2000-2003  Dave Jones, Arjan van de Ven, Janne Pänkälä,
   *                 Dominik Brodowski.

   *
   *  Licensed under the terms of the GNU GPL License version 2.
   *
   *  BIG FAT DISCLAIMER: Work in progress code. Possibly *dangerous*
   */
  
  #include <linux/kernel.h>

  #include <linux/module.h>

  #include <linux/init.h>
  #include <linux/cpufreq.h>
  #include <linux/ioport.h>

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

  #include <asm/msr.h>

  #define POWERNOW_IOPORT 0xfff0          /* it doesn't matter where, as long
  					   as it is unused */

  #define PFX "powernow-k6: "

  static unsigned int                     busfreq;   /* FSB, in 10 kHz */
  static unsigned int                     max_multiplier;
  
  
  /* Clock ratio multiplied by 10 - see table 27 in AMD#23446 */
  static struct cpufreq_frequency_table clock_ratio[] = {
  	{45,  /* 000 -> 4.5x */ 0},
  	{50,  /* 001 -> 5.0x */ 0},
  	{40,  /* 010 -> 4.0x */ 0},
  	{55,  /* 011 -> 5.5x */ 0},
  	{20,  /* 100 -> 2.0x */ 0},
  	{30,  /* 101 -> 3.0x */ 0},
  	{60,  /* 110 -> 6.0x */ 0},
  	{35,  /* 111 -> 3.5x */ 0},
  	{0, CPUFREQ_TABLE_END}
  };
  
  
  /**
   * powernow_k6_get_cpu_multiplier - returns the current FSB multiplier
   *
   *   Returns the current setting of the frequency multiplier. Core clock
   * speed is frequency of the Front-Side Bus multiplied with this value.
   */
  static int powernow_k6_get_cpu_multiplier(void)
  {

  	u64 invalue = 0;
  	u32 msrval;

  	msrval = POWERNOW_IOPORT + 0x1;
  	wrmsr(MSR_K6_EPMR, msrval, 0); /* enable the PowerNow port */

  	invalue = inl(POWERNOW_IOPORT + 0x8);

  	msrval = POWERNOW_IOPORT + 0x0;
  	wrmsr(MSR_K6_EPMR, msrval, 0); /* disable it again */
  
  	return clock_ratio[(invalue >> 5)&7].index;
  }
  
  
  /**
   * powernow_k6_set_state - set the PowerNow! multiplier
   * @best_i: clock_ratio[best_i] is the target multiplier
   *
   *   Tries to change the PowerNow! multiplier
   */

  static void powernow_k6_set_state(unsigned int best_i)

  {

  	unsigned long outvalue = 0, invalue = 0;
  	unsigned long msrval;
  	struct cpufreq_freqs freqs;

  
  	if (clock_ratio[best_i].index > max_multiplier) {

  		printk(KERN_ERR PFX "invalid target frequency
  ");

  		return;
  	}
  
  	freqs.old = busfreq * powernow_k6_get_cpu_multiplier();
  	freqs.new = busfreq * clock_ratio[best_i].index;
  	freqs.cpu = 0; /* powernow-k6.c is UP only driver */

  	cpufreq_notify_transition(&freqs, CPUFREQ_PRECHANGE);
  
  	/* we now need to transform best_i to the BVC format, see AMD#23446 */
  
  	outvalue = (1<<12) | (1<<10) | (1<<9) | (best_i<<5);
  
  	msrval = POWERNOW_IOPORT + 0x1;
  	wrmsr(MSR_K6_EPMR, msrval, 0); /* enable the PowerNow port */

  	invalue = inl(POWERNOW_IOPORT + 0x8);

  	invalue = invalue & 0xf;
  	outvalue = outvalue | invalue;

  	outl(outvalue , (POWERNOW_IOPORT + 0x8));

  	msrval = POWERNOW_IOPORT + 0x0;
  	wrmsr(MSR_K6_EPMR, msrval, 0); /* disable it again */
  
  	cpufreq_notify_transition(&freqs, CPUFREQ_POSTCHANGE);
  
  	return;
  }
  
  
  /**
   * powernow_k6_verify - verifies a new CPUfreq policy
   * @policy: new policy
   *
   * Policy must be within lowest and highest possible CPU Frequency,
   * and at least one possible state must be within min and max.
   */
  static int powernow_k6_verify(struct cpufreq_policy *policy)
  {
  	return cpufreq_frequency_table_verify(policy, &clock_ratio[0]);
  }
  
  
  /**
   * powernow_k6_setpolicy - sets a new CPUFreq policy
   * @policy: new policy
   * @target_freq: the target frequency

   * @relation: how that frequency relates to achieved frequency
   *  (CPUFREQ_RELATION_L or CPUFREQ_RELATION_H)

   *
   * sets a new CPUFreq policy
   */

  static int powernow_k6_target(struct cpufreq_policy *policy,

  			       unsigned int target_freq,
  			       unsigned int relation)
  {

  	unsigned int newstate = 0;

  	if (cpufreq_frequency_table_target(policy, &clock_ratio[0],
  				target_freq, relation, &newstate))

  		return -EINVAL;
  
  	powernow_k6_set_state(newstate);
  
  	return 0;
  }
  
  
  static int powernow_k6_cpu_init(struct cpufreq_policy *policy)
  {

  	unsigned int i, f;

  	int result;
  
  	if (policy->cpu != 0)
  		return -ENODEV;
  
  	/* get frequencies */
  	max_multiplier = powernow_k6_get_cpu_multiplier();
  	busfreq = cpu_khz / max_multiplier;
  
  	/* table init */

  	for (i = 0; (clock_ratio[i].frequency != CPUFREQ_TABLE_END); i++) {

  		f = clock_ratio[i].index;
  		if (f > max_multiplier)

  			clock_ratio[i].frequency = CPUFREQ_ENTRY_INVALID;
  		else

  			clock_ratio[i].frequency = busfreq * f;

  	}
  
  	/* cpuinfo and default policy values */

  	policy->cpuinfo.transition_latency = 200000;

  	policy->cur = busfreq * max_multiplier;
  
  	result = cpufreq_frequency_table_cpuinfo(policy, clock_ratio);
  	if (result)

  		return result;

  
  	cpufreq_frequency_table_get_attr(clock_ratio, policy->cpu);
  
  	return 0;
  }
  
  
  static int powernow_k6_cpu_exit(struct cpufreq_policy *policy)
  {
  	unsigned int i;

  	for (i = 0; i < 8; i++) {
  		if (i == max_multiplier)

  			powernow_k6_set_state(i);
  	}
  	cpufreq_frequency_table_put_attr(policy->cpu);

  	return 0;

  }
  
  static unsigned int powernow_k6_get(unsigned int cpu)
  {

  	unsigned int ret;
  	ret = (busfreq * powernow_k6_get_cpu_multiplier());
  	return ret;

  }

  static struct freq_attr *powernow_k6_attr[] = {

  	&cpufreq_freq_attr_scaling_available_freqs,
  	NULL,
  };

  static struct cpufreq_driver powernow_k6_driver = {

  	.verify		= powernow_k6_verify,
  	.target		= powernow_k6_target,

  	.init		= powernow_k6_cpu_init,
  	.exit		= powernow_k6_cpu_exit,
  	.get		= powernow_k6_get,
  	.name		= "powernow-k6",
  	.owner		= THIS_MODULE,
  	.attr		= powernow_k6_attr,
  };
  
  
  /**
   * powernow_k6_init - initializes the k6 PowerNow! CPUFreq driver
   *
   *   Initializes the K6 PowerNow! support. Returns -ENODEV on unsupported
   * devices, -EINVAL or -ENOMEM on problems during initiatization, and zero
   * on success.
   */
  static int __init powernow_k6_init(void)

  {

  	struct cpuinfo_x86 *c = &cpu_data(0);

  
  	if ((c->x86_vendor != X86_VENDOR_AMD) || (c->x86 != 5) ||
  		((c->x86_model != 12) && (c->x86_model != 13)))
  		return -ENODEV;
  
  	if (!request_region(POWERNOW_IOPORT, 16, "PowerNow!")) {

  		printk(KERN_INFO PFX "PowerNow IOPORT region already used.
  ");

  		return -EIO;
  	}
  
  	if (cpufreq_register_driver(&powernow_k6_driver)) {

  		release_region(POWERNOW_IOPORT, 16);

  		return -EINVAL;
  	}
  
  	return 0;
  }
  
  
  /**
   * powernow_k6_exit - unregisters AMD K6-2+/3+ PowerNow! support
   *
   *   Unregisters AMD K6-2+ / K6-3+ PowerNow! support.
   */
  static void __exit powernow_k6_exit(void)
  {
  	cpufreq_unregister_driver(&powernow_k6_driver);

  	release_region(POWERNOW_IOPORT, 16);

  }

  MODULE_AUTHOR("Arjan van de Ven, Dave Jones <davej@redhat.com>, "
  		"Dominik Brodowski <linux@brodo.de>");

  MODULE_DESCRIPTION("PowerNow! driver for AMD K6-2+ / K6-3+ processors.");
  MODULE_LICENSE("GPL");

  
  module_init(powernow_k6_init);
  module_exit(powernow_k6_exit);