linux/drivers/cpufreq/longrun.c
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   1/*
   2 * (C) 2002 - 2003  Dominik Brodowski <linux@brodo.de>
   3 *
   4 *  Licensed under the terms of the GNU GPL License version 2.
   5 *
   6 *  BIG FAT DISCLAIMER: Work in progress code. Possibly *dangerous*
   7 */
   8
   9#include <linux/kernel.h>
  10#include <linux/module.h>
  11#include <linux/init.h>
  12#include <linux/cpufreq.h>
  13#include <linux/timex.h>
  14
  15#include <asm/msr.h>
  16#include <asm/processor.h>
  17#include <asm/cpu_device_id.h>
  18
  19static struct cpufreq_driver    longrun_driver;
  20
  21/**
  22 * longrun_{low,high}_freq is needed for the conversion of cpufreq kHz
  23 * values into per cent values. In TMTA microcode, the following is valid:
  24 * performance_pctg = (current_freq - low_freq)/(high_freq - low_freq)
  25 */
  26static unsigned int longrun_low_freq, longrun_high_freq;
  27
  28
  29/**
  30 * longrun_get_policy - get the current LongRun policy
  31 * @policy: struct cpufreq_policy where current policy is written into
  32 *
  33 * Reads the current LongRun policy by access to MSR_TMTA_LONGRUN_FLAGS
  34 * and MSR_TMTA_LONGRUN_CTRL
  35 */
  36static void longrun_get_policy(struct cpufreq_policy *policy)
  37{
  38        u32 msr_lo, msr_hi;
  39
  40        rdmsr(MSR_TMTA_LONGRUN_FLAGS, msr_lo, msr_hi);
  41        pr_debug("longrun flags are %x - %x\n", msr_lo, msr_hi);
  42        if (msr_lo & 0x01)
  43                policy->policy = CPUFREQ_POLICY_PERFORMANCE;
  44        else
  45                policy->policy = CPUFREQ_POLICY_POWERSAVE;
  46
  47        rdmsr(MSR_TMTA_LONGRUN_CTRL, msr_lo, msr_hi);
  48        pr_debug("longrun ctrl is %x - %x\n", msr_lo, msr_hi);
  49        msr_lo &= 0x0000007F;
  50        msr_hi &= 0x0000007F;
  51
  52        if (longrun_high_freq <= longrun_low_freq) {
  53                /* Assume degenerate Longrun table */
  54                policy->min = policy->max = longrun_high_freq;
  55        } else {
  56                policy->min = longrun_low_freq + msr_lo *
  57                        ((longrun_high_freq - longrun_low_freq) / 100);
  58                policy->max = longrun_low_freq + msr_hi *
  59                        ((longrun_high_freq - longrun_low_freq) / 100);
  60        }
  61        policy->cpu = 0;
  62}
  63
  64
  65/**
  66 * longrun_set_policy - sets a new CPUFreq policy
  67 * @policy: new policy
  68 *
  69 * Sets a new CPUFreq policy on LongRun-capable processors. This function
  70 * has to be called with cpufreq_driver locked.
  71 */
  72static int longrun_set_policy(struct cpufreq_policy *policy)
  73{
  74        u32 msr_lo, msr_hi;
  75        u32 pctg_lo, pctg_hi;
  76
  77        if (!policy)
  78                return -EINVAL;
  79
  80        if (longrun_high_freq <= longrun_low_freq) {
  81                /* Assume degenerate Longrun table */
  82                pctg_lo = pctg_hi = 100;
  83        } else {
  84                pctg_lo = (policy->min - longrun_low_freq) /
  85                        ((longrun_high_freq - longrun_low_freq) / 100);
  86                pctg_hi = (policy->max - longrun_low_freq) /
  87                        ((longrun_high_freq - longrun_low_freq) / 100);
  88        }
  89
  90        if (pctg_hi > 100)
  91                pctg_hi = 100;
  92        if (pctg_lo > pctg_hi)
  93                pctg_lo = pctg_hi;
  94
  95        /* performance or economy mode */
  96        rdmsr(MSR_TMTA_LONGRUN_FLAGS, msr_lo, msr_hi);
  97        msr_lo &= 0xFFFFFFFE;
  98        switch (policy->policy) {
  99        case CPUFREQ_POLICY_PERFORMANCE:
 100                msr_lo |= 0x00000001;
 101                break;
 102        case CPUFREQ_POLICY_POWERSAVE:
 103                break;
 104        }
 105        wrmsr(MSR_TMTA_LONGRUN_FLAGS, msr_lo, msr_hi);
 106
 107        /* lower and upper boundary */
 108        rdmsr(MSR_TMTA_LONGRUN_CTRL, msr_lo, msr_hi);
 109        msr_lo &= 0xFFFFFF80;
 110        msr_hi &= 0xFFFFFF80;
 111        msr_lo |= pctg_lo;
 112        msr_hi |= pctg_hi;
 113        wrmsr(MSR_TMTA_LONGRUN_CTRL, msr_lo, msr_hi);
 114
 115        return 0;
 116}
 117
 118
 119/**
 120 * longrun_verify_poliy - verifies a new CPUFreq policy
 121 * @policy: the policy to verify
 122 *
 123 * Validates a new CPUFreq policy. This function has to be called with
 124 * cpufreq_driver locked.
 125 */
 126static int longrun_verify_policy(struct cpufreq_policy *policy)
 127{
 128        if (!policy)
 129                return -EINVAL;
 130
 131        policy->cpu = 0;
 132        cpufreq_verify_within_limits(policy,
 133                policy->cpuinfo.min_freq,
 134                policy->cpuinfo.max_freq);
 135
 136        if ((policy->policy != CPUFREQ_POLICY_POWERSAVE) &&
 137            (policy->policy != CPUFREQ_POLICY_PERFORMANCE))
 138                return -EINVAL;
 139
 140        return 0;
 141}
 142
 143static unsigned int longrun_get(unsigned int cpu)
 144{
 145        u32 eax, ebx, ecx, edx;
 146
 147        if (cpu)
 148                return 0;
 149
 150        cpuid(0x80860007, &eax, &ebx, &ecx, &edx);
 151        pr_debug("cpuid eax is %u\n", eax);
 152
 153        return eax * 1000;
 154}
 155
 156/**
 157 * longrun_determine_freqs - determines the lowest and highest possible core frequency
 158 * @low_freq: an int to put the lowest frequency into
 159 * @high_freq: an int to put the highest frequency into
 160 *
 161 * Determines the lowest and highest possible core frequencies on this CPU.
 162 * This is necessary to calculate the performance percentage according to
 163 * TMTA rules:
 164 * performance_pctg = (target_freq - low_freq)/(high_freq - low_freq)
 165 */
 166static int longrun_determine_freqs(unsigned int *low_freq,
 167                                                      unsigned int *high_freq)
 168{
 169        u32 msr_lo, msr_hi;
 170        u32 save_lo, save_hi;
 171        u32 eax, ebx, ecx, edx;
 172        u32 try_hi;
 173        struct cpuinfo_x86 *c = &cpu_data(0);
 174
 175        if (!low_freq || !high_freq)
 176                return -EINVAL;
 177
 178        if (cpu_has(c, X86_FEATURE_LRTI)) {
 179                /* if the LongRun Table Interface is present, the
 180                 * detection is a bit easier:
 181                 * For minimum frequency, read out the maximum
 182                 * level (msr_hi), write that into "currently
 183                 * selected level", and read out the frequency.
 184                 * For maximum frequency, read out level zero.
 185                 */
 186                /* minimum */
 187                rdmsr(MSR_TMTA_LRTI_READOUT, msr_lo, msr_hi);
 188                wrmsr(MSR_TMTA_LRTI_READOUT, msr_hi, msr_hi);
 189                rdmsr(MSR_TMTA_LRTI_VOLT_MHZ, msr_lo, msr_hi);
 190                *low_freq = msr_lo * 1000; /* to kHz */
 191
 192                /* maximum */
 193                wrmsr(MSR_TMTA_LRTI_READOUT, 0, msr_hi);
 194                rdmsr(MSR_TMTA_LRTI_VOLT_MHZ, msr_lo, msr_hi);
 195                *high_freq = msr_lo * 1000; /* to kHz */
 196
 197                pr_debug("longrun table interface told %u - %u kHz\n",
 198                                *low_freq, *high_freq);
 199
 200                if (*low_freq > *high_freq)
 201                        *low_freq = *high_freq;
 202                return 0;
 203        }
 204
 205        /* set the upper border to the value determined during TSC init */
 206        *high_freq = (cpu_khz / 1000);
 207        *high_freq = *high_freq * 1000;
 208        pr_debug("high frequency is %u kHz\n", *high_freq);
 209
 210        /* get current borders */
 211        rdmsr(MSR_TMTA_LONGRUN_CTRL, msr_lo, msr_hi);
 212        save_lo = msr_lo & 0x0000007F;
 213        save_hi = msr_hi & 0x0000007F;
 214
 215        /* if current perf_pctg is larger than 90%, we need to decrease the
 216         * upper limit to make the calculation more accurate.
 217         */
 218        cpuid(0x80860007, &eax, &ebx, &ecx, &edx);
 219        /* try decreasing in 10% steps, some processors react only
 220         * on some barrier values */
 221        for (try_hi = 80; try_hi > 0 && ecx > 90; try_hi -= 10) {
 222                /* set to 0 to try_hi perf_pctg */
 223                msr_lo &= 0xFFFFFF80;
 224                msr_hi &= 0xFFFFFF80;
 225                msr_hi |= try_hi;
 226                wrmsr(MSR_TMTA_LONGRUN_CTRL, msr_lo, msr_hi);
 227
 228                /* read out current core MHz and current perf_pctg */
 229                cpuid(0x80860007, &eax, &ebx, &ecx, &edx);
 230
 231                /* restore values */
 232                wrmsr(MSR_TMTA_LONGRUN_CTRL, save_lo, save_hi);
 233        }
 234        pr_debug("percentage is %u %%, freq is %u MHz\n", ecx, eax);
 235
 236        /* performance_pctg = (current_freq - low_freq)/(high_freq - low_freq)
 237         * eqals
 238         * low_freq * (1 - perf_pctg) = (cur_freq - high_freq * perf_pctg)
 239         *
 240         * high_freq * perf_pctg is stored tempoarily into "ebx".
 241         */
 242        ebx = (((cpu_khz / 1000) * ecx) / 100); /* to MHz */
 243
 244        if ((ecx > 95) || (ecx == 0) || (eax < ebx))
 245                return -EIO;
 246
 247        edx = ((eax - ebx) * 100) / (100 - ecx);
 248        *low_freq = edx * 1000; /* back to kHz */
 249
 250        pr_debug("low frequency is %u kHz\n", *low_freq);
 251
 252        if (*low_freq > *high_freq)
 253                *low_freq = *high_freq;
 254
 255        return 0;
 256}
 257
 258
 259static int longrun_cpu_init(struct cpufreq_policy *policy)
 260{
 261        int result = 0;
 262
 263        /* capability check */
 264        if (policy->cpu != 0)
 265                return -ENODEV;
 266
 267        /* detect low and high frequency */
 268        result = longrun_determine_freqs(&longrun_low_freq, &longrun_high_freq);
 269        if (result)
 270                return result;
 271
 272        /* cpuinfo and default policy values */
 273        policy->cpuinfo.min_freq = longrun_low_freq;
 274        policy->cpuinfo.max_freq = longrun_high_freq;
 275        policy->cpuinfo.transition_latency = CPUFREQ_ETERNAL;
 276        longrun_get_policy(policy);
 277
 278        return 0;
 279}
 280
 281
 282static struct cpufreq_driver longrun_driver = {
 283        .flags          = CPUFREQ_CONST_LOOPS,
 284        .verify         = longrun_verify_policy,
 285        .setpolicy      = longrun_set_policy,
 286        .get            = longrun_get,
 287        .init           = longrun_cpu_init,
 288        .name           = "longrun",
 289        .owner          = THIS_MODULE,
 290};
 291
 292static const struct x86_cpu_id longrun_ids[] = {
 293        { X86_VENDOR_TRANSMETA, X86_FAMILY_ANY, X86_MODEL_ANY,
 294          X86_FEATURE_LONGRUN },
 295        {}
 296};
 297MODULE_DEVICE_TABLE(x86cpu, longrun_ids);
 298
 299/**
 300 * longrun_init - initializes the Transmeta Crusoe LongRun CPUFreq driver
 301 *
 302 * Initializes the LongRun support.
 303 */
 304static int __init longrun_init(void)
 305{
 306        if (!x86_match_cpu(longrun_ids))
 307                return -ENODEV;
 308        return cpufreq_register_driver(&longrun_driver);
 309}
 310
 311
 312/**
 313 * longrun_exit - unregisters LongRun support
 314 */
 315static void __exit longrun_exit(void)
 316{
 317        cpufreq_unregister_driver(&longrun_driver);
 318}
 319
 320
 321MODULE_AUTHOR("Dominik Brodowski <linux@brodo.de>");
 322MODULE_DESCRIPTION("LongRun driver for Transmeta Crusoe and "
 323                "Efficeon processors.");
 324MODULE_LICENSE("GPL");
 325
 326module_init(longrun_init);
 327module_exit(longrun_exit);
 328
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