drivers/cpufreq/longrun.c

   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
  19 static 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  */
  26 static 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  */
  36 static 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  */
  72 static 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  */
 126 static 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
 143 static 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  */
 166 static 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
 259 static 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
 282 static 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 };
 290
 291 static const struct x86_cpu_id longrun_ids[] = {
 292         { X86_VENDOR_TRANSMETA, X86_FAMILY_ANY, X86_MODEL_ANY,
 293           X86_FEATURE_LONGRUN },
 294         {}
 295 };
 296 MODULE_DEVICE_TABLE(x86cpu, longrun_ids);
 297
 298 /**
 299  * longrun_init - initializes the Transmeta Crusoe LongRun CPUFreq driver
 300  *
 301  * Initializes the LongRun support.
 302  */
 303 static int __init longrun_init(void)
 304 {
 305         if (!x86_match_cpu(longrun_ids))
 306                 return -ENODEV;
 307         return cpufreq_register_driver(&longrun_driver);
 308 }
 309
 310
 311 /**
 312  * longrun_exit - unregisters LongRun support
 313  */
 314 static void __exit longrun_exit(void)
 315 {
 316         cpufreq_unregister_driver(&longrun_driver);
 317 }
 318
 319
 320 MODULE_AUTHOR("Dominik Brodowski <linux@brodo.de>");
 321 MODULE_DESCRIPTION("LongRun driver for Transmeta Crusoe and "
 322                 "Efficeon processors.");
 323 MODULE_LICENSE("GPL");
 324
 325 module_init(longrun_init);
 326 module_exit(longrun_exit);