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longrun.c

/*
 * (C) 2002 - 2003  Dominik Brodowski <linux@brodo.de>
 *
 *  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/slab.h>
#include <linux/cpufreq.h>

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

#define dprintk(msg...) cpufreq_debug_printk(CPUFREQ_DEBUG_DRIVER, "longrun", msg)

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 __init longrun_get_policy(struct cpufreq_policy *policy)
{
      u32 msr_lo, msr_hi;

      rdmsr(MSR_TMTA_LONGRUN_FLAGS, msr_lo, msr_hi);
      dprintk("longrun flags are %x - %x\n", 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);
      dprintk("longrun ctrl is %x - %x\n", 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 *policy)
{
      if (!policy)
            return -EINVAL;

      policy->cpu = 0;
      cpufreq_verify_within_limits(policy,
            policy->cpuinfo.min_freq,
            policy->cpuinfo.max_freq);

      if ((policy->policy != CPUFREQ_POLICY_POWERSAVE) &&
          (policy->policy != CPUFREQ_POLICY_PERFORMANCE))
            return -EINVAL;

      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);
      dprintk("cpuid eax is %u\n", 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 unsigned int __init 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 */

            dprintk("longrun table interface told %u - %u kHz\n", *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;
      dprintk("high frequency is %u kHz\n", *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);
      }
      dprintk("percentage is %u %%, freq is %u MHz\n", 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 - ecx);
      *low_freq = edx * 1000; /* back to kHz */

      dprintk("low frequency is %u kHz\n", *low_freq);

      if (*low_freq > *high_freq)
            *low_freq = *high_freq;

      return 0;
}


static int __init 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;
      policy->cpuinfo.transition_latency = CPUFREQ_ETERNAL;
      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",
      .owner            = THIS_MODULE,
};


/**
 * longrun_init - initializes the Transmeta Crusoe LongRun CPUFreq driver
 *
 * Initializes the LongRun support.
 */
static int __init longrun_init(void)
{
      struct cpuinfo_x86 *c = &cpu_data(0);

      if (c->x86_vendor != X86_VENDOR_TRANSMETA ||
          !cpu_has(c, X86_FEATURE_LONGRUN))
            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);

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