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         policy->min = longrun_low_freq + msr_lo *
  51                 ((longrun_high_freq - longrun_low_freq) / 100);
  52         policy->max = longrun_low_freq + msr_hi *
  53                 ((longrun_high_freq - longrun_low_freq) / 100);
  54         policy->cpu = 0;
  55 }
  56
  57
  58 /**
  59  * longrun_set_policy - sets a new CPUFreq policy
  60  * @policy: new policy
  61  *
  62  * Sets a new CPUFreq policy on LongRun-capable processors. This function
  63  * has to be called with cpufreq_driver locked.
  64  */
  65 static int longrun_set_policy(struct cpufreq_policy *policy)
  66 {
  67         u32 msr_lo, msr_hi;
  68         u32 pctg_lo, pctg_hi;
  69
  70         if (!policy)
  71                 return -EINVAL;
  72
  73         pctg_lo = (policy->min - longrun_low_freq) /
  74                 ((longrun_high_freq - longrun_low_freq) / 100);
  75         pctg_hi = (policy->max - longrun_low_freq) /
  76                 ((longrun_high_freq - longrun_low_freq) / 100);
  77
  78         if (pctg_hi > 100)
  79                 pctg_hi = 100;
  80         if (pctg_lo > pctg_hi)
  81                 pctg_lo = pctg_hi;
  82
  83         /* performance or economy mode */
  84         rdmsr(MSR_TMTA_LONGRUN_FLAGS, msr_lo, msr_hi);
  85         msr_lo &= 0xFFFFFFFE;
  86         switch (policy->policy) {
  87         case CPUFREQ_POLICY_PERFORMANCE:
  88                 msr_lo |= 0x00000001;
  89                 break;
  90         case CPUFREQ_POLICY_POWERSAVE:
  91                 break;
  92         }
  93         wrmsr(MSR_TMTA_LONGRUN_FLAGS, msr_lo, msr_hi);
  94
  95         /* lower and upper boundary */
  96         rdmsr(MSR_TMTA_LONGRUN_CTRL, msr_lo, msr_hi);
  97         msr_lo &= 0xFFFFFF80;
  98         msr_hi &= 0xFFFFFF80;
  99         msr_lo |= pctg_lo;
 100         msr_hi |= pctg_hi;
 101         wrmsr(MSR_TMTA_LONGRUN_CTRL, msr_lo, msr_hi);
 102
 103         return 0;
 104 }
 105
 106
 107 /**
 108  * longrun_verify_poliy - verifies a new CPUFreq policy
 109  * @policy: the policy to verify
 110  *
 111  * Validates a new CPUFreq policy. This function has to be called with
 112  * cpufreq_driver locked.
 113  */
 114 static int longrun_verify_policy(struct cpufreq_policy *policy)
 115 {
 116         if (!policy)
 117                 return -EINVAL;
 118
 119         policy->cpu = 0;
 120         cpufreq_verify_within_limits(policy,
 121                 policy->cpuinfo.min_freq,
 122                 policy->cpuinfo.max_freq);
 123
 124         if ((policy->policy != CPUFREQ_POLICY_POWERSAVE) &&
 125             (policy->policy != CPUFREQ_POLICY_PERFORMANCE))
 126                 return -EINVAL;
 127
 128         return 0;
 129 }
 130
 131
 132 /**
 133  * longrun_determine_freqs - determines the lowest and highest possible core frequency
 134  * @low_freq: an int to put the lowest frequency into
 135  * @high_freq: an int to put the highest frequency into
 136  *
 137  * Determines the lowest and highest possible core frequencies on this CPU.
 138  * This is necessary to calculate the performance percentage according to
 139  * TMTA rules:
 140  * performance_pctg = (target_freq - low_freq)/(high_freq - low_freq)
 141  */
 142 static unsigned int __init longrun_determine_freqs(unsigned int *low_freq,
 143                                                    unsigned int *high_freq)
 144 {
 145         u32 msr_lo, msr_hi;
 146         u32 save_lo, save_hi;
 147         u32 eax, ebx, ecx, edx;
 148         u32 try_hi;
 149         struct cpuinfo_x86 *c = cpu_data;
 150
 151         if (!low_freq || !high_freq)
 152                 return -EINVAL;
 153
 154         if (cpu_has(c, X86_FEATURE_LRTI)) {
 155                 /* if the LongRun Table Interface is present, the
 156                  * detection is a bit easier:
 157                  * For minimum frequency, read out the maximum
 158                  * level (msr_hi), write that into "currently
 159                  * selected level", and read out the frequency.
 160                  * For maximum frequency, read out level zero.
 161                  */
 162                 /* minimum */
 163                 rdmsr(MSR_TMTA_LRTI_READOUT, msr_lo, msr_hi);
 164                 wrmsr(MSR_TMTA_LRTI_READOUT, msr_hi, msr_hi);
 165                 rdmsr(MSR_TMTA_LRTI_VOLT_MHZ, msr_lo, msr_hi);
 166                 *low_freq = msr_lo * 1000; /* to kHz */
 167
 168                 /* maximum */
 169                 wrmsr(MSR_TMTA_LRTI_READOUT, 0, msr_hi);
 170                 rdmsr(MSR_TMTA_LRTI_VOLT_MHZ, msr_lo, msr_hi);
 171                 *high_freq = msr_lo * 1000; /* to kHz */
 172
 173                 if (*low_freq > *high_freq)
 174                         *low_freq = *high_freq;
 175                 return 0;
 176         }
 177
 178         /* set the upper border to the value determined during TSC init */
 179         *high_freq = (cpu_khz / 1000);
 180         *high_freq = *high_freq * 1000;
 181
 182         /* get current borders */
 183         rdmsr(MSR_TMTA_LONGRUN_CTRL, msr_lo, msr_hi);
 184         save_lo = msr_lo & 0x0000007F;
 185         save_hi = msr_hi & 0x0000007F;
 186
 187         /* if current perf_pctg is larger than 90%, we need to decrease the
 188          * upper limit to make the calculation more accurate.
 189          */
 190         cpuid(0x80860007, &eax, &ebx, &ecx, &edx);
 191         /* try decreasing in 10% steps, some processors react only
 192          * on some barrier values */
 193         for (try_hi = 80; try_hi > 0 && ecx > 90; try_hi -=10) {
 194                 /* set to 0 to try_hi perf_pctg */
 195                 msr_lo &= 0xFFFFFF80;
 196                 msr_hi &= 0xFFFFFF80;
 197                 msr_lo |= 0;
 198                 msr_hi |= try_hi;
 199                 wrmsr(MSR_TMTA_LONGRUN_CTRL, msr_lo, msr_hi);
 200
 201                 /* read out current core MHz and current perf_pctg */
 202                 cpuid(0x80860007, &eax, &ebx, &ecx, &edx);
 203
 204                 /* restore values */
 205                 wrmsr(MSR_TMTA_LONGRUN_CTRL, save_lo, save_hi);
 206         }
 207
 208         /* performance_pctg = (current_freq - low_freq)/(high_freq - low_freq)
 209          * eqals
 210          * low_freq * ( 1 - perf_pctg) = (cur_freq - high_freq * perf_pctg)
 211          *
 212          * high_freq * perf_pctg is stored tempoarily into "ebx".
 213          */
 214         ebx = (((cpu_khz / 1000) * ecx) / 100); /* to MHz */
 215
 216         if ((ecx > 95) || (ecx == 0) || (eax < ebx))
 217                 return -EIO;
 218
 219         edx = (eax - ebx) / (100 - ecx);
 220         *low_freq = edx * 1000; /* back to kHz */
 221
 222         if (*low_freq > *high_freq)
 223                 *low_freq = *high_freq;
 224
 225         return 0;
 226 }
 227
 228
 229 static int __init longrun_cpu_init(struct cpufreq_policy *policy)
 230 {
 231         int                     result = 0;
 232
 233         /* capability check */
 234         if (policy->cpu != 0)
 235                 return -ENODEV;
 236
 237         /* detect low and high frequency */
 238         result = longrun_determine_freqs(&longrun_low_freq, &longrun_high_freq);
 239         if (result)
 240                 return result;
 241
 242         /* cpuinfo and default policy values */
 243         policy->cpuinfo.min_freq = longrun_low_freq;
 244         policy->cpuinfo.max_freq = longrun_high_freq;
 245         policy->cpuinfo.transition_latency = CPUFREQ_ETERNAL;
 246         longrun_get_policy(policy);
 247
 248         return 0;
 249 }
 250
 251
 252 static struct cpufreq_driver longrun_driver = {
 253         .verify         = longrun_verify_policy,
 254         .setpolicy      = longrun_set_policy,
 255         .init           = longrun_cpu_init,
 256         .name           = "longrun",
 257         .owner          = THIS_MODULE,
 258 };
 259
 260
 261 /**
 262  * longrun_init - initializes the Transmeta Crusoe LongRun CPUFreq driver
 263  *
 264  * Initializes the LongRun support.
 265  */
 266 static int __init longrun_init(void)
 267 {
 268         struct cpuinfo_x86 *c = cpu_data;
 269
 270         if (c->x86_vendor != X86_VENDOR_TRANSMETA ||
 271             !cpu_has(c, X86_FEATURE_LONGRUN))
 272                 return -ENODEV;
 273
 274         return cpufreq_register_driver(&longrun_driver);
 275 }
 276
 277
 278 /**
 279  * longrun_exit - unregisters LongRun support
 280  */
 281 static void __exit longrun_exit(void)
 282 {
 283         cpufreq_unregister_driver(&longrun_driver);
 284 }
 285
 286
 287 MODULE_AUTHOR ("Dominik Brodowski <linux@brodo.de>");
 288 MODULE_DESCRIPTION ("LongRun driver for Transmeta Crusoe processors.");
 289 MODULE_LICENSE ("GPL");
 290
 291 module_init(longrun_init);
 292 module_exit(longrun_exit);