drivers/cpufreq/longrun.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * (C) 2002 - 2003  Dominik Brodowski <linux@brodo.de>
   4  *
   5  *  BIG FAT DISCLAIMER: Work in progress code. Possibly *dangerous*
   6  */
   7
   8 #include <linux/kernel.h>
   9 #include <linux/module.h>
  10 #include <linux/init.h>
  11 #include <linux/cpufreq.h>
  12 #include <linux/timex.h>
  13
  14 #include <asm/msr.h>
  15 #include <asm/processor.h>
  16 #include <asm/cpu_device_id.h>
  17
  18 static struct cpufreq_driver    longrun_driver;
  19
  20 /**
  21  * longrun_{low,high}_freq is needed for the conversion of cpufreq kHz
  22  * values into per cent values. In TMTA microcode, the following is valid:
  23  * performance_pctg = (current_freq - low_freq)/(high_freq - low_freq)
  24  */
  25 static unsigned int longrun_low_freq, longrun_high_freq;
  26
  27
  28 /**
  29  * longrun_get_policy - get the current LongRun policy
  30  * @policy: struct cpufreq_policy where current policy is written into
  31  *
  32  * Reads the current LongRun policy by access to MSR_TMTA_LONGRUN_FLAGS
  33  * and MSR_TMTA_LONGRUN_CTRL
  34  */
  35 static void longrun_get_policy(struct cpufreq_policy *policy)
  36 {
  37         u32 msr_lo, msr_hi;
  38
  39         rdmsr(MSR_TMTA_LONGRUN_FLAGS, msr_lo, msr_hi);
  40         pr_debug("longrun flags are %x - %x\n", msr_lo, msr_hi);
  41         if (msr_lo & 0x01)
  42                 policy->policy = CPUFREQ_POLICY_PERFORMANCE;
  43         else
  44                 policy->policy = CPUFREQ_POLICY_POWERSAVE;
  45
  46         rdmsr(MSR_TMTA_LONGRUN_CTRL, msr_lo, msr_hi);
  47         pr_debug("longrun ctrl is %x - %x\n", msr_lo, msr_hi);
  48         msr_lo &= 0x0000007F;
  49         msr_hi &= 0x0000007F;
  50
  51         if (longrun_high_freq <= longrun_low_freq) {
  52                 /* Assume degenerate Longrun table */
  53                 policy->min = policy->max = longrun_high_freq;
  54         } else {
  55                 policy->min = longrun_low_freq + msr_lo *
  56                         ((longrun_high_freq - longrun_low_freq) / 100);
  57                 policy->max = longrun_low_freq + msr_hi *
  58                         ((longrun_high_freq - longrun_low_freq) / 100);
  59         }
  60         policy->cpu = 0;
  61 }
  62
  63
  64 /**
  65  * longrun_set_policy - sets a new CPUFreq policy
  66  * @policy: new policy
  67  *
  68  * Sets a new CPUFreq policy on LongRun-capable processors. This function
  69  * has to be called with cpufreq_driver locked.
  70  */
  71 static int longrun_set_policy(struct cpufreq_policy *policy)
  72 {
  73         u32 msr_lo, msr_hi;
  74         u32 pctg_lo, pctg_hi;
  75
  76         if (!policy)
  77                 return -EINVAL;
  78
  79         if (longrun_high_freq <= longrun_low_freq) {
  80                 /* Assume degenerate Longrun table */
  81                 pctg_lo = pctg_hi = 100;
  82         } else {
  83                 pctg_lo = (policy->min - longrun_low_freq) /
  84                         ((longrun_high_freq - longrun_low_freq) / 100);
  85                 pctg_hi = (policy->max - longrun_low_freq) /
  86                         ((longrun_high_freq - longrun_low_freq) / 100);
  87         }
  88
  89         if (pctg_hi > 100)
  90                 pctg_hi = 100;
  91         if (pctg_lo > pctg_hi)
  92                 pctg_lo = pctg_hi;
  93
  94         /* performance or economy mode */
  95         rdmsr(MSR_TMTA_LONGRUN_FLAGS, msr_lo, msr_hi);
  96         msr_lo &= 0xFFFFFFFE;
  97         switch (policy->policy) {
  98         case CPUFREQ_POLICY_PERFORMANCE:
  99                 msr_lo |= 0x00000001;
 100                 break;
 101         case CPUFREQ_POLICY_POWERSAVE:
 102                 break;
 103         }
 104         wrmsr(MSR_TMTA_LONGRUN_FLAGS, msr_lo, msr_hi);
 105
 106         /* lower and upper boundary */
 107         rdmsr(MSR_TMTA_LONGRUN_CTRL, msr_lo, msr_hi);
 108         msr_lo &= 0xFFFFFF80;
 109         msr_hi &= 0xFFFFFF80;
 110         msr_lo |= pctg_lo;
 111         msr_hi |= pctg_hi;
 112         wrmsr(MSR_TMTA_LONGRUN_CTRL, msr_lo, msr_hi);
 113
 114         return 0;
 115 }
 116
 117
 118 /**
 119  * longrun_verify_poliy - verifies a new CPUFreq policy
 120  * @policy: the policy to verify
 121  *
 122  * Validates a new CPUFreq policy. This function has to be called with
 123  * cpufreq_driver locked.
 124  */
 125 static int longrun_verify_policy(struct cpufreq_policy *policy)
 126 {
 127         if (!policy)
 128                 return -EINVAL;
 129
 130         policy->cpu = 0;
 131         cpufreq_verify_within_cpu_limits(policy);
 132
 133         if ((policy->policy != CPUFREQ_POLICY_POWERSAVE) &&
 134             (policy->policy != CPUFREQ_POLICY_PERFORMANCE))
 135                 return -EINVAL;
 136
 137         return 0;
 138 }
 139
 140 static unsigned int longrun_get(unsigned int cpu)
 141 {
 142         u32 eax, ebx, ecx, edx;
 143
 144         if (cpu)
 145                 return 0;
 146
 147         cpuid(0x80860007, &eax, &ebx, &ecx, &edx);
 148         pr_debug("cpuid eax is %u\n", eax);
 149
 150         return eax * 1000;
 151 }
 152
 153 /**
 154  * longrun_determine_freqs - determines the lowest and highest possible core frequency
 155  * @low_freq: an int to put the lowest frequency into
 156  * @high_freq: an int to put the highest frequency into
 157  *
 158  * Determines the lowest and highest possible core frequencies on this CPU.
 159  * This is necessary to calculate the performance percentage according to
 160  * TMTA rules:
 161  * performance_pctg = (target_freq - low_freq)/(high_freq - low_freq)
 162  */
 163 static int longrun_determine_freqs(unsigned int *low_freq,
 164                                                       unsigned int *high_freq)
 165 {
 166         u32 msr_lo, msr_hi;
 167         u32 save_lo, save_hi;
 168         u32 eax, ebx, ecx, edx;
 169         u32 try_hi;
 170         struct cpuinfo_x86 *c = &cpu_data(0);
 171
 172         if (!low_freq || !high_freq)
 173                 return -EINVAL;
 174
 175         if (cpu_has(c, X86_FEATURE_LRTI)) {
 176                 /* if the LongRun Table Interface is present, the
 177                  * detection is a bit easier:
 178                  * For minimum frequency, read out the maximum
 179                  * level (msr_hi), write that into "currently
 180                  * selected level", and read out the frequency.
 181                  * For maximum frequency, read out level zero.
 182                  */
 183                 /* minimum */
 184                 rdmsr(MSR_TMTA_LRTI_READOUT, msr_lo, msr_hi);
 185                 wrmsr(MSR_TMTA_LRTI_READOUT, msr_hi, msr_hi);
 186                 rdmsr(MSR_TMTA_LRTI_VOLT_MHZ, msr_lo, msr_hi);
 187                 *low_freq = msr_lo * 1000; /* to kHz */
 188
 189                 /* maximum */
 190                 wrmsr(MSR_TMTA_LRTI_READOUT, 0, msr_hi);
 191                 rdmsr(MSR_TMTA_LRTI_VOLT_MHZ, msr_lo, msr_hi);
 192                 *high_freq = msr_lo * 1000; /* to kHz */
 193
 194                 pr_debug("longrun table interface told %u - %u kHz\n",
 195                                 *low_freq, *high_freq);
 196
 197                 if (*low_freq > *high_freq)
 198                         *low_freq = *high_freq;
 199                 return 0;
 200         }
 201
 202         /* set the upper border to the value determined during TSC init */
 203         *high_freq = (cpu_khz / 1000);
 204         *high_freq = *high_freq * 1000;
 205         pr_debug("high frequency is %u kHz\n", *high_freq);
 206
 207         /* get current borders */
 208         rdmsr(MSR_TMTA_LONGRUN_CTRL, msr_lo, msr_hi);
 209         save_lo = msr_lo & 0x0000007F;
 210         save_hi = msr_hi & 0x0000007F;
 211
 212         /* if current perf_pctg is larger than 90%, we need to decrease the
 213          * upper limit to make the calculation more accurate.
 214          */
 215         cpuid(0x80860007, &eax, &ebx, &ecx, &edx);
 216         /* try decreasing in 10% steps, some processors react only
 217          * on some barrier values */
 218         for (try_hi = 80; try_hi > 0 && ecx > 90; try_hi -= 10) {
 219                 /* set to 0 to try_hi perf_pctg */
 220                 msr_lo &= 0xFFFFFF80;
 221                 msr_hi &= 0xFFFFFF80;
 222                 msr_hi |= try_hi;
 223                 wrmsr(MSR_TMTA_LONGRUN_CTRL, msr_lo, msr_hi);
 224
 225                 /* read out current core MHz and current perf_pctg */
 226                 cpuid(0x80860007, &eax, &ebx, &ecx, &edx);
 227
 228                 /* restore values */
 229                 wrmsr(MSR_TMTA_LONGRUN_CTRL, save_lo, save_hi);
 230         }
 231         pr_debug("percentage is %u %%, freq is %u MHz\n", ecx, eax);
 232
 233         /* performance_pctg = (current_freq - low_freq)/(high_freq - low_freq)
 234          * eqals
 235          * low_freq * (1 - perf_pctg) = (cur_freq - high_freq * perf_pctg)
 236          *
 237          * high_freq * perf_pctg is stored tempoarily into "ebx".
 238          */
 239         ebx = (((cpu_khz / 1000) * ecx) / 100); /* to MHz */
 240
 241         if ((ecx > 95) || (ecx == 0) || (eax < ebx))
 242                 return -EIO;
 243
 244         edx = ((eax - ebx) * 100) / (100 - ecx);
 245         *low_freq = edx * 1000; /* back to kHz */
 246
 247         pr_debug("low frequency is %u kHz\n", *low_freq);
 248
 249         if (*low_freq > *high_freq)
 250                 *low_freq = *high_freq;
 251
 252         return 0;
 253 }
 254
 255
 256 static int longrun_cpu_init(struct cpufreq_policy *policy)
 257 {
 258         int result = 0;
 259
 260         /* capability check */
 261         if (policy->cpu != 0)
 262                 return -ENODEV;
 263
 264         /* detect low and high frequency */
 265         result = longrun_determine_freqs(&longrun_low_freq, &longrun_high_freq);
 266         if (result)
 267                 return result;
 268
 269         /* cpuinfo and default policy values */
 270         policy->cpuinfo.min_freq = longrun_low_freq;
 271         policy->cpuinfo.max_freq = longrun_high_freq;
 272         longrun_get_policy(policy);
 273
 274         return 0;
 275 }
 276
 277
 278 static struct cpufreq_driver longrun_driver = {
 279         .flags          = CPUFREQ_CONST_LOOPS,
 280         .verify         = longrun_verify_policy,
 281         .setpolicy      = longrun_set_policy,
 282         .get            = longrun_get,
 283         .init           = longrun_cpu_init,
 284         .name           = "longrun",
 285 };
 286
 287 static const struct x86_cpu_id longrun_ids[] = {
 288         { X86_VENDOR_TRANSMETA, X86_FAMILY_ANY, X86_MODEL_ANY,
 289           X86_FEATURE_LONGRUN },
 290         {}
 291 };
 292 MODULE_DEVICE_TABLE(x86cpu, longrun_ids);
 293
 294 /**
 295  * longrun_init - initializes the Transmeta Crusoe LongRun CPUFreq driver
 296  *
 297  * Initializes the LongRun support.
 298  */
 299 static int __init longrun_init(void)
 300 {
 301         if (!x86_match_cpu(longrun_ids))
 302                 return -ENODEV;
 303         return cpufreq_register_driver(&longrun_driver);
 304 }
 305
 306
 307 /**
 308  * longrun_exit - unregisters LongRun support
 309  */
 310 static void __exit longrun_exit(void)
 311 {
 312         cpufreq_unregister_driver(&longrun_driver);
 313 }
 314
 315
 316 MODULE_AUTHOR("Dominik Brodowski <linux@brodo.de>");
 317 MODULE_DESCRIPTION("LongRun driver for Transmeta Crusoe and "
 318                 "Efficeon processors.");
 319 MODULE_LICENSE("GPL");
 320
 321 module_init(longrun_init);
 322 module_exit(longrun_exit);