arch/i386/kernel/cpu/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/slab.h>
  13 #include <linux/cpufreq.h>
  14
  15 #include <asm/msr.h>
  16 #include <asm/processor.h>
  17 #include <asm/timex.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 __init 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         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         msr_lo &= 0x0000007F;
  48         msr_hi &= 0x0000007F;
  49
  50         if ( longrun_high_freq <= longrun_low_freq ) {
  51                 /* Assume degenerate Longrun table */
  52                 policy->min = policy->max = longrun_high_freq;
  53         } else {
  54                 policy->min = longrun_low_freq + msr_lo *
  55                         ((longrun_high_freq - longrun_low_freq) / 100);
  56                 policy->max = longrun_low_freq + msr_hi *
  57                         ((longrun_high_freq - longrun_low_freq) / 100);
  58         }
  59         policy->cpu = 0;
  60 }
  61
  62
  63 /**
  64  * longrun_set_policy - sets a new CPUFreq policy
  65  * @policy: new policy
  66  *
  67  * Sets a new CPUFreq policy on LongRun-capable processors. This function
  68  * has to be called with cpufreq_driver locked.
  69  */
  70 static int longrun_set_policy(struct cpufreq_policy *policy)
  71 {
  72         u32 msr_lo, msr_hi;
  73         u32 pctg_lo, pctg_hi;
  74
  75         if (!policy)
  76                 return -EINVAL;
  77
  78         if ( longrun_high_freq <= longrun_low_freq ) {
  79                 /* Assume degenerate Longrun table */
  80                 pctg_lo = pctg_hi = 100;
  81         } else {
  82                 pctg_lo = (policy->min - longrun_low_freq) /
  83                         ((longrun_high_freq - longrun_low_freq) / 100);
  84                 pctg_hi = (policy->max - longrun_low_freq) /
  85                         ((longrun_high_freq - longrun_low_freq) / 100);
  86         }
  87
  88         if (pctg_hi > 100)
  89                 pctg_hi = 100;
  90         if (pctg_lo > pctg_hi)
  91                 pctg_lo = pctg_hi;
  92
  93         /* performance or economy mode */
  94         rdmsr(MSR_TMTA_LONGRUN_FLAGS, msr_lo, msr_hi);
  95         msr_lo &= 0xFFFFFFFE;
  96         switch (policy->policy) {
  97         case CPUFREQ_POLICY_PERFORMANCE:
  98                 msr_lo |= 0x00000001;
  99                 break;
 100         case CPUFREQ_POLICY_POWERSAVE:
 101                 break;
 102         }
 103         wrmsr(MSR_TMTA_LONGRUN_FLAGS, msr_lo, msr_hi);
 104
 105         /* lower and upper boundary */
 106         rdmsr(MSR_TMTA_LONGRUN_CTRL, msr_lo, msr_hi);
 107         msr_lo &= 0xFFFFFF80;
 108         msr_hi &= 0xFFFFFF80;
 109         msr_lo |= pctg_lo;
 110         msr_hi |= pctg_hi;
 111         wrmsr(MSR_TMTA_LONGRUN_CTRL, msr_lo, msr_hi);
 112
 113         return 0;
 114 }
 115
 116
 117 /**
 118  * longrun_verify_poliy - verifies a new CPUFreq policy
 119  * @policy: the policy to verify
 120  *
 121  * Validates a new CPUFreq policy. This function has to be called with
 122  * cpufreq_driver locked.
 123  */
 124 static int longrun_verify_policy(struct cpufreq_policy *policy)
 125 {
 126         if (!policy)
 127                 return -EINVAL;
 128
 129         policy->cpu = 0;
 130         cpufreq_verify_within_limits(policy,
 131                 policy->cpuinfo.min_freq,
 132                 policy->cpuinfo.max_freq);
 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
 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 unsigned int __init 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;
 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                 if (*low_freq > *high_freq)
 195                         *low_freq = *high_freq;
 196                 return 0;
 197         }
 198
 199         /* set the upper border to the value determined during TSC init */
 200         *high_freq = (cpu_khz / 1000);
 201         *high_freq = *high_freq * 1000;
 202
 203         /* get current borders */
 204         rdmsr(MSR_TMTA_LONGRUN_CTRL, msr_lo, msr_hi);
 205         save_lo = msr_lo & 0x0000007F;
 206         save_hi = msr_hi & 0x0000007F;
 207
 208         /* if current perf_pctg is larger than 90%, we need to decrease the
 209          * upper limit to make the calculation more accurate.
 210          */
 211         cpuid(0x80860007, &eax, &ebx, &ecx, &edx);
 212         /* try decreasing in 10% steps, some processors react only
 213          * on some barrier values */
 214         for (try_hi = 80; try_hi > 0 && ecx > 90; try_hi -=10) {
 215                 /* set to 0 to try_hi perf_pctg */
 216                 msr_lo &= 0xFFFFFF80;
 217                 msr_hi &= 0xFFFFFF80;
 218                 msr_lo |= 0;
 219                 msr_hi |= try_hi;
 220                 wrmsr(MSR_TMTA_LONGRUN_CTRL, msr_lo, msr_hi);
 221
 222                 /* read out current core MHz and current perf_pctg */
 223                 cpuid(0x80860007, &eax, &ebx, &ecx, &edx);
 224
 225                 /* restore values */
 226                 wrmsr(MSR_TMTA_LONGRUN_CTRL, save_lo, save_hi);
 227         }
 228
 229         /* performance_pctg = (current_freq - low_freq)/(high_freq - low_freq)
 230          * eqals
 231          * low_freq * ( 1 - perf_pctg) = (cur_freq - high_freq * perf_pctg)
 232          *
 233          * high_freq * perf_pctg is stored tempoarily into "ebx".
 234          */
 235         ebx = (((cpu_khz / 1000) * ecx) / 100); /* to MHz */
 236
 237         if ((ecx > 95) || (ecx == 0) || (eax < ebx))
 238                 return -EIO;
 239
 240         edx = (eax - ebx) / (100 - ecx);
 241         *low_freq = edx * 1000; /* back to kHz */
 242
 243         if (*low_freq > *high_freq)
 244                 *low_freq = *high_freq;
 245
 246         return 0;
 247 }
 248
 249
 250 static int __init longrun_cpu_init(struct cpufreq_policy *policy)
 251 {
 252         int                     result = 0;
 253
 254         /* capability check */
 255         if (policy->cpu != 0)
 256                 return -ENODEV;
 257
 258         /* detect low and high frequency */
 259         result = longrun_determine_freqs(&longrun_low_freq, &longrun_high_freq);
 260         if (result)
 261                 return result;
 262
 263         /* cpuinfo and default policy values */
 264         policy->cpuinfo.min_freq = longrun_low_freq;
 265         policy->cpuinfo.max_freq = longrun_high_freq;
 266         policy->cpuinfo.transition_latency = CPUFREQ_ETERNAL;
 267         longrun_get_policy(policy);
 268
 269         return 0;
 270 }
 271
 272
 273 static struct cpufreq_driver longrun_driver = {
 274         .flags          = CPUFREQ_CONST_LOOPS,
 275         .verify         = longrun_verify_policy,
 276         .setpolicy      = longrun_set_policy,
 277         .get            = longrun_get,
 278         .init           = longrun_cpu_init,
 279         .name           = "longrun",
 280         .owner          = THIS_MODULE,
 281 };
 282
 283
 284 /**
 285  * longrun_init - initializes the Transmeta Crusoe LongRun CPUFreq driver
 286  *
 287  * Initializes the LongRun support.
 288  */
 289 static int __init longrun_init(void)
 290 {
 291         struct cpuinfo_x86 *c = cpu_data;
 292
 293         if (c->x86_vendor != X86_VENDOR_TRANSMETA ||
 294             !cpu_has(c, X86_FEATURE_LONGRUN))
 295                 return -ENODEV;
 296
 297         return cpufreq_register_driver(&longrun_driver);
 298 }
 299
 300
 301 /**
 302  * longrun_exit - unregisters LongRun support
 303  */
 304 static void __exit longrun_exit(void)
 305 {
 306         cpufreq_unregister_driver(&longrun_driver);
 307 }
 308
 309
 310 MODULE_AUTHOR ("Dominik Brodowski <linux@brodo.de>");
 311 MODULE_DESCRIPTION ("LongRun driver for Transmeta Crusoe processors.");
 312 MODULE_LICENSE ("GPL");
 313
 314 module_init(longrun_init);
 315 module_exit(longrun_exit);