// SPDX-License-Identifier: GPL-2.0-only

  /*
   * (C) 2002 - 2003  Dominik Brodowski <linux@brodo.de>
   *

   *  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/timex.h>

  
  #include <asm/msr.h>
  #include <asm/processor.h>

  #include <asm/cpu_device_id.h>

  static struct cpufreq_driver	longrun_driver;

  
  /**
   * longrun_{low,high}_freq is needed for the conversion of cpufreq kHz
   * values into per cent values. In TMTA microcode, the following is valid:
   * performance_pctg = (current_freq - low_freq)/(high_freq - low_freq)
   */
  static unsigned int longrun_low_freq, longrun_high_freq;
  
  
  /**
   * longrun_get_policy - get the current LongRun policy
   * @policy: struct cpufreq_policy where current policy is written into
   *
   * Reads the current LongRun policy by access to MSR_TMTA_LONGRUN_FLAGS
   * and MSR_TMTA_LONGRUN_CTRL
   */

  static void longrun_get_policy(struct cpufreq_policy *policy)

  {
  	u32 msr_lo, msr_hi;
  
  	rdmsr(MSR_TMTA_LONGRUN_FLAGS, msr_lo, msr_hi);

  	pr_debug("longrun flags are %x - %x
  ", msr_lo, msr_hi);

  	if (msr_lo & 0x01)
  		policy->policy = CPUFREQ_POLICY_PERFORMANCE;
  	else
  		policy->policy = CPUFREQ_POLICY_POWERSAVE;
  
  	rdmsr(MSR_TMTA_LONGRUN_CTRL, msr_lo, msr_hi);

  	pr_debug("longrun ctrl is %x - %x
  ", msr_lo, msr_hi);

  	msr_lo &= 0x0000007F;
  	msr_hi &= 0x0000007F;

  	if (longrun_high_freq <= longrun_low_freq) {

  		/* Assume degenerate Longrun table */
  		policy->min = policy->max = longrun_high_freq;
  	} else {
  		policy->min = longrun_low_freq + msr_lo *
  			((longrun_high_freq - longrun_low_freq) / 100);
  		policy->max = longrun_low_freq + msr_hi *
  			((longrun_high_freq - longrun_low_freq) / 100);
  	}
  	policy->cpu = 0;
  }
  
  
  /**
   * longrun_set_policy - sets a new CPUFreq policy
   * @policy: new policy
   *
   * Sets a new CPUFreq policy on LongRun-capable processors. This function
   * has to be called with cpufreq_driver locked.
   */
  static int longrun_set_policy(struct cpufreq_policy *policy)
  {
  	u32 msr_lo, msr_hi;
  	u32 pctg_lo, pctg_hi;
  
  	if (!policy)
  		return -EINVAL;

  	if (longrun_high_freq <= longrun_low_freq) {

  		/* Assume degenerate Longrun table */
  		pctg_lo = pctg_hi = 100;
  	} else {
  		pctg_lo = (policy->min - longrun_low_freq) /
  			((longrun_high_freq - longrun_low_freq) / 100);
  		pctg_hi = (policy->max - longrun_low_freq) /
  			((longrun_high_freq - longrun_low_freq) / 100);
  	}
  
  	if (pctg_hi > 100)
  		pctg_hi = 100;
  	if (pctg_lo > pctg_hi)
  		pctg_lo = pctg_hi;
  
  	/* performance or economy mode */
  	rdmsr(MSR_TMTA_LONGRUN_FLAGS, msr_lo, msr_hi);
  	msr_lo &= 0xFFFFFFFE;
  	switch (policy->policy) {
  	case CPUFREQ_POLICY_PERFORMANCE:
  		msr_lo |= 0x00000001;
  		break;
  	case CPUFREQ_POLICY_POWERSAVE:
  		break;
  	}
  	wrmsr(MSR_TMTA_LONGRUN_FLAGS, msr_lo, msr_hi);
  
  	/* lower and upper boundary */
  	rdmsr(MSR_TMTA_LONGRUN_CTRL, msr_lo, msr_hi);
  	msr_lo &= 0xFFFFFF80;
  	msr_hi &= 0xFFFFFF80;
  	msr_lo |= pctg_lo;
  	msr_hi |= pctg_hi;
  	wrmsr(MSR_TMTA_LONGRUN_CTRL, msr_lo, msr_hi);
  
  	return 0;
  }
  
  
  /**
   * longrun_verify_poliy - verifies a new CPUFreq policy
   * @policy: the policy to verify
   *
   * Validates a new CPUFreq policy. This function has to be called with
   * cpufreq_driver locked.
   */

  static int longrun_verify_policy(struct cpufreq_policy_data *policy)

  {
  	if (!policy)
  		return -EINVAL;
  
  	policy->cpu = 0;

  	cpufreq_verify_within_cpu_limits(policy);

  	return 0;
  }
  
  static unsigned int longrun_get(unsigned int cpu)
  {
  	u32 eax, ebx, ecx, edx;
  
  	if (cpu)
  		return 0;
  
  	cpuid(0x80860007, &eax, &ebx, &ecx, &edx);

  	pr_debug("cpuid eax is %u
  ", eax);

  	return eax * 1000;

  }
  
  /**
   * longrun_determine_freqs - determines the lowest and highest possible core frequency
   * @low_freq: an int to put the lowest frequency into
   * @high_freq: an int to put the highest frequency into
   *
   * Determines the lowest and highest possible core frequencies on this CPU.
   * This is necessary to calculate the performance percentage according to
   * TMTA rules:
   * performance_pctg = (target_freq - low_freq)/(high_freq - low_freq)
   */

  static int longrun_determine_freqs(unsigned int *low_freq,

  						      unsigned int *high_freq)

  {
  	u32 msr_lo, msr_hi;
  	u32 save_lo, save_hi;
  	u32 eax, ebx, ecx, edx;
  	u32 try_hi;

  	struct cpuinfo_x86 *c = &cpu_data(0);

  
  	if (!low_freq || !high_freq)
  		return -EINVAL;
  
  	if (cpu_has(c, X86_FEATURE_LRTI)) {
  		/* if the LongRun Table Interface is present, the
  		 * detection is a bit easier:
  		 * For minimum frequency, read out the maximum
  		 * level (msr_hi), write that into "currently
  		 * selected level", and read out the frequency.
  		 * For maximum frequency, read out level zero.
  		 */
  		/* minimum */
  		rdmsr(MSR_TMTA_LRTI_READOUT, msr_lo, msr_hi);
  		wrmsr(MSR_TMTA_LRTI_READOUT, msr_hi, msr_hi);
  		rdmsr(MSR_TMTA_LRTI_VOLT_MHZ, msr_lo, msr_hi);
  		*low_freq = msr_lo * 1000; /* to kHz */
  
  		/* maximum */
  		wrmsr(MSR_TMTA_LRTI_READOUT, 0, msr_hi);
  		rdmsr(MSR_TMTA_LRTI_VOLT_MHZ, msr_lo, msr_hi);
  		*high_freq = msr_lo * 1000; /* to kHz */

  		pr_debug("longrun table interface told %u - %u kHz
  ",

  				*low_freq, *high_freq);

  
  		if (*low_freq > *high_freq)
  			*low_freq = *high_freq;
  		return 0;
  	}
  
  	/* set the upper border to the value determined during TSC init */
  	*high_freq = (cpu_khz / 1000);
  	*high_freq = *high_freq * 1000;

  	pr_debug("high frequency is %u kHz
  ", *high_freq);

  
  	/* get current borders */
  	rdmsr(MSR_TMTA_LONGRUN_CTRL, msr_lo, msr_hi);
  	save_lo = msr_lo & 0x0000007F;
  	save_hi = msr_hi & 0x0000007F;
  
  	/* if current perf_pctg is larger than 90%, we need to decrease the
  	 * upper limit to make the calculation more accurate.
  	 */
  	cpuid(0x80860007, &eax, &ebx, &ecx, &edx);
  	/* try decreasing in 10% steps, some processors react only
  	 * on some barrier values */

  	for (try_hi = 80; try_hi > 0 && ecx > 90; try_hi -= 10) {

  		/* set to 0 to try_hi perf_pctg */
  		msr_lo &= 0xFFFFFF80;
  		msr_hi &= 0xFFFFFF80;

  		msr_hi |= try_hi;
  		wrmsr(MSR_TMTA_LONGRUN_CTRL, msr_lo, msr_hi);
  
  		/* read out current core MHz and current perf_pctg */
  		cpuid(0x80860007, &eax, &ebx, &ecx, &edx);
  
  		/* restore values */
  		wrmsr(MSR_TMTA_LONGRUN_CTRL, save_lo, save_hi);
  	}

  	pr_debug("percentage is %u %%, freq is %u MHz
  ", ecx, eax);

  
  	/* performance_pctg = (current_freq - low_freq)/(high_freq - low_freq)
  	 * eqals

  	 * low_freq * (1 - perf_pctg) = (cur_freq - high_freq * perf_pctg)

  	 *
  	 * high_freq * perf_pctg is stored tempoarily into "ebx".
  	 */
  	ebx = (((cpu_khz / 1000) * ecx) / 100); /* to MHz */
  
  	if ((ecx > 95) || (ecx == 0) || (eax < ebx))
  		return -EIO;

  	edx = ((eax - ebx) * 100) / (100 - ecx);

  	*low_freq = edx * 1000; /* back to kHz */

  	pr_debug("low frequency is %u kHz
  ", *low_freq);

  
  	if (*low_freq > *high_freq)
  		*low_freq = *high_freq;
  
  	return 0;
  }

  static int longrun_cpu_init(struct cpufreq_policy *policy)

  {
  	int result = 0;
  
  	/* capability check */
  	if (policy->cpu != 0)
  		return -ENODEV;
  
  	/* detect low and high frequency */
  	result = longrun_determine_freqs(&longrun_low_freq, &longrun_high_freq);
  	if (result)
  		return result;
  
  	/* cpuinfo and default policy values */
  	policy->cpuinfo.min_freq = longrun_low_freq;
  	policy->cpuinfo.max_freq = longrun_high_freq;

  	longrun_get_policy(policy);
  
  	return 0;
  }

  static struct cpufreq_driver longrun_driver = {

  	.flags		= CPUFREQ_CONST_LOOPS,
  	.verify		= longrun_verify_policy,
  	.setpolicy	= longrun_set_policy,
  	.get		= longrun_get,
  	.init		= longrun_cpu_init,
  	.name		= "longrun",

  };

  static const struct x86_cpu_id longrun_ids[] = {

  	X86_MATCH_VENDOR_FEATURE(TRANSMETA, X86_FEATURE_LONGRUN, NULL),

  	{}
  };
  MODULE_DEVICE_TABLE(x86cpu, longrun_ids);

  
  /**
   * longrun_init - initializes the Transmeta Crusoe LongRun CPUFreq driver
   *
   * Initializes the LongRun support.
   */
  static int __init longrun_init(void)
  {

  	if (!x86_match_cpu(longrun_ids))

  		return -ENODEV;

  	return cpufreq_register_driver(&longrun_driver);
  }
  
  
  /**
   * longrun_exit - unregisters LongRun support
   */
  static void __exit longrun_exit(void)
  {
  	cpufreq_unregister_driver(&longrun_driver);
  }

  MODULE_AUTHOR("Dominik Brodowski <linux@brodo.de>");
  MODULE_DESCRIPTION("LongRun driver for Transmeta Crusoe and "
  		"Efficeon processors.");
  MODULE_LICENSE("GPL");

  
  module_init(longrun_init);
  module_exit(longrun_exit);