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_cpu_limits(policy);
 133
 134         if ((policy->policy != CPUFREQ_POLICY_POWERSAVE) &&
 135             (policy->policy != CPUFREQ_POLICY_PERFORMANCE))
 136                 return -EINVAL;
 137
 138         return 0;
 139 }
 140
 141 static unsigned int longrun_get(unsigned int cpu)
 142 {
 143         u32 eax, ebx, ecx, edx;
 144
 145         if (cpu)
 146                 return 0;
 147
 148         cpuid(0x80860007, &eax, &ebx, &ecx, &edx);
 149         pr_debug("cpuid eax is %u\n", eax);
 150
 151         return eax * 1000;
 152 }
 153
 154 /**
 155  * longrun_determine_freqs - determines the lowest and highest possible core frequency
 156  * @low_freq: an int to put the lowest frequency into
 157  * @high_freq: an int to put the highest frequency into
 158  *
 159  * Determines the lowest and highest possible core frequencies on this CPU.
 160  * This is necessary to calculate the performance percentage according to
 161  * TMTA rules:
 162  * performance_pctg = (target_freq - low_freq)/(high_freq - low_freq)
 163  */
 164 static int longrun_determine_freqs(unsigned int *low_freq,
 165                                                       unsigned int *high_freq)
 166 {
 167         u32 msr_lo, msr_hi;
 168         u32 save_lo, save_hi;
 169         u32 eax, ebx, ecx, edx;
 170         u32 try_hi;
 171         struct cpuinfo_x86 *c = &cpu_data(0);
 172
 173         if (!low_freq || !high_freq)
 174                 return -EINVAL;
 175
 176         if (cpu_has(c, X86_FEATURE_LRTI)) {
 177                 /* if the LongRun Table Interface is present, the
 178                  * detection is a bit easier:
 179                  * For minimum frequency, read out the maximum
 180                  * level (msr_hi), write that into "currently
 181                  * selected level", and read out the frequency.
 182                  * For maximum frequency, read out level zero.
 183                  */
 184                 /* minimum */
 185                 rdmsr(MSR_TMTA_LRTI_READOUT, msr_lo, msr_hi);
 186                 wrmsr(MSR_TMTA_LRTI_READOUT, msr_hi, msr_hi);
 187                 rdmsr(MSR_TMTA_LRTI_VOLT_MHZ, msr_lo, msr_hi);
 188                 *low_freq = msr_lo * 1000; /* to kHz */
 189
 190                 /* maximum */
 191                 wrmsr(MSR_TMTA_LRTI_READOUT, 0, msr_hi);
 192                 rdmsr(MSR_TMTA_LRTI_VOLT_MHZ, msr_lo, msr_hi);
 193                 *high_freq = msr_lo * 1000; /* to kHz */
 194
 195                 pr_debug("longrun table interface told %u - %u kHz\n",
 196                                 *low_freq, *high_freq);
 197
 198                 if (*low_freq > *high_freq)
 199                         *low_freq = *high_freq;
 200                 return 0;
 201         }
 202
 203         /* set the upper border to the value determined during TSC init */
 204         *high_freq = (cpu_khz / 1000);
 205         *high_freq = *high_freq * 1000;
 206         pr_debug("high frequency is %u kHz\n", *high_freq);
 207
 208         /* get current borders */
 209         rdmsr(MSR_TMTA_LONGRUN_CTRL, msr_lo, msr_hi);
 210         save_lo = msr_lo & 0x0000007F;
 211         save_hi = msr_hi & 0x0000007F;
 212
 213         /* if current perf_pctg is larger than 90%, we need to decrease the
 214          * upper limit to make the calculation more accurate.
 215          */
 216         cpuid(0x80860007, &eax, &ebx, &ecx, &edx);
 217         /* try decreasing in 10% steps, some processors react only
 218          * on some barrier values */
 219         for (try_hi = 80; try_hi > 0 && ecx > 90; try_hi -= 10) {
 220                 /* set to 0 to try_hi perf_pctg */
 221                 msr_lo &= 0xFFFFFF80;
 222                 msr_hi &= 0xFFFFFF80;
 223                 msr_hi |= try_hi;
 224                 wrmsr(MSR_TMTA_LONGRUN_CTRL, msr_lo, msr_hi);
 225
 226                 /* read out current core MHz and current perf_pctg */
 227                 cpuid(0x80860007, &eax, &ebx, &ecx, &edx);
 228
 229                 /* restore values */
 230                 wrmsr(MSR_TMTA_LONGRUN_CTRL, save_lo, save_hi);
 231         }
 232         pr_debug("percentage is %u %%, freq is %u MHz\n", ecx, eax);
 233
 234         /* performance_pctg = (current_freq - low_freq)/(high_freq - low_freq)
 235          * eqals
 236          * low_freq * (1 - perf_pctg) = (cur_freq - high_freq * perf_pctg)
 237          *
 238          * high_freq * perf_pctg is stored tempoarily into "ebx".
 239          */
 240         ebx = (((cpu_khz / 1000) * ecx) / 100); /* to MHz */
 241
 242         if ((ecx > 95) || (ecx == 0) || (eax < ebx))
 243                 return -EIO;
 244
 245         edx = ((eax - ebx) * 100) / (100 - ecx);
 246         *low_freq = edx * 1000; /* back to kHz */
 247
 248         pr_debug("low frequency is %u kHz\n", *low_freq);
 249
 250         if (*low_freq > *high_freq)
 251                 *low_freq = *high_freq;
 252
 253         return 0;
 254 }
 255
 256
 257 static int longrun_cpu_init(struct cpufreq_policy *policy)
 258 {
 259         int result = 0;
 260
 261         /* capability check */
 262         if (policy->cpu != 0)
 263                 return -ENODEV;
 264
 265         /* detect low and high frequency */
 266         result = longrun_determine_freqs(&longrun_low_freq, &longrun_high_freq);
 267         if (result)
 268                 return result;
 269
 270         /* cpuinfo and default policy values */
 271         policy->cpuinfo.min_freq = longrun_low_freq;
 272         policy->cpuinfo.max_freq = longrun_high_freq;
 273         policy->cpuinfo.transition_latency = CPUFREQ_ETERNAL;
 274         longrun_get_policy(policy);
 275
 276         return 0;
 277 }
 278
 279
 280 static struct cpufreq_driver longrun_driver = {
 281         .flags          = CPUFREQ_CONST_LOOPS,
 282         .verify         = longrun_verify_policy,
 283         .setpolicy      = longrun_set_policy,
 284         .get            = longrun_get,
 285         .init           = longrun_cpu_init,
 286         .name           = "longrun",
 287 };
 288
 289 static const struct x86_cpu_id longrun_ids[] = {
 290         { X86_VENDOR_TRANSMETA, X86_FAMILY_ANY, X86_MODEL_ANY,
 291           X86_FEATURE_LONGRUN },
 292         {}
 293 };
 294 MODULE_DEVICE_TABLE(x86cpu, longrun_ids);
 295
 296 /**
 297  * longrun_init - initializes the Transmeta Crusoe LongRun CPUFreq driver
 298  *
 299  * Initializes the LongRun support.
 300  */
 301 static int __init longrun_init(void)
 302 {
 303         if (!x86_match_cpu(longrun_ids))
 304                 return -ENODEV;
 305         return cpufreq_register_driver(&longrun_driver);
 306 }
 307
 308
 309 /**
 310  * longrun_exit - unregisters LongRun support
 311  */
 312 static void __exit longrun_exit(void)
 313 {
 314         cpufreq_unregister_driver(&longrun_driver);
 315 }
 316
 317
 318 MODULE_AUTHOR("Dominik Brodowski <linux@brodo.de>");
 319 MODULE_DESCRIPTION("LongRun driver for Transmeta Crusoe and "
 320                 "Efficeon processors.");
 321 MODULE_LICENSE("GPL");
 322
 323 module_init(longrun_init);
 324 module_exit(longrun_exit);