LXR linux/drivers/cpufreq/speedstep-lib.c

   1// SPDX-License-Identifier: GPL-2.0-only
   2/*
   3 * (C) 2002 - 2003 Dominik Brodowski <linux@brodo.de>
   4 *
   5 *  Library for common functions for Intel SpeedStep v.1 and v.2 support
   6 *
   7 *  BIG FAT DISCLAIMER: Work in progress code. Possibly *dangerous*
   8 */
   9
  10#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  11
  12#include <linux/kernel.h>
  13#include <linux/module.h>
  14#include <linux/moduleparam.h>
  15#include <linux/init.h>
  16#include <linux/cpufreq.h>
  17
  18#include <asm/msr.h>
  19#include <asm/tsc.h>
  20#include "speedstep-lib.h"
  21
  22#define PFX "speedstep-lib: "
  23
  24#ifdef CONFIG_X86_SPEEDSTEP_RELAXED_CAP_CHECK
  25static int relaxed_check;
  26#else
  27#define relaxed_check 0
  28#endif
  29
  30/*********************************************************************
  31 *                   GET PROCESSOR CORE SPEED IN KHZ                 *
  32 *********************************************************************/
  33
  34static unsigned int pentium3_get_frequency(enum speedstep_processor processor)
  35{
  36        /* See table 14 of p3_ds.pdf and table 22 of 29834003.pdf */
  37        static const struct {
  38                unsigned int ratio;     /* Frequency Multiplier (x10) */
  39                u8 bitmap;              /* power on configuration bits
  40                                        [27, 25:22] (in MSR 0x2a) */
  41        } msr_decode_mult[] = {
  42                { 30, 0x01 },
  43                { 35, 0x05 },
  44                { 40, 0x02 },
  45                { 45, 0x06 },
  46                { 50, 0x00 },
  47                { 55, 0x04 },
  48                { 60, 0x0b },
  49                { 65, 0x0f },
  50                { 70, 0x09 },
  51                { 75, 0x0d },
  52                { 80, 0x0a },
  53                { 85, 0x26 },
  54                { 90, 0x20 },
  55                { 100, 0x2b },
  56                { 0, 0xff }     /* error or unknown value */
  57        };
  58
  59        /* PIII(-M) FSB settings: see table b1-b of 24547206.pdf */
  60        static const struct {
  61                unsigned int value;     /* Front Side Bus speed in MHz */
  62                u8 bitmap;              /* power on configuration bits [18: 19]
  63                                        (in MSR 0x2a) */
  64        } msr_decode_fsb[] = {
  65                {  66, 0x0 },
  66                { 100, 0x2 },
  67                { 133, 0x1 },
  68                {   0, 0xff}
  69        };
  70
  71        u32 msr_lo, msr_tmp;
  72        int i = 0, j = 0;
  73
  74        /* read MSR 0x2a - we only need the low 32 bits */
  75        rdmsr(MSR_IA32_EBL_CR_POWERON, msr_lo, msr_tmp);
  76        pr_debug("P3 - MSR_IA32_EBL_CR_POWERON: 0x%x 0x%x\n", msr_lo, msr_tmp);
  77        msr_tmp = msr_lo;
  78
  79        /* decode the FSB */
  80        msr_tmp &= 0x00c0000;
  81        msr_tmp >>= 18;
  82        while (msr_tmp != msr_decode_fsb[i].bitmap) {
  83                if (msr_decode_fsb[i].bitmap == 0xff)
  84                        return 0;
  85                i++;
  86        }
  87
  88        /* decode the multiplier */
  89        if (processor == SPEEDSTEP_CPU_PIII_C_EARLY) {
  90                pr_debug("workaround for early PIIIs\n");
  91                msr_lo &= 0x03c00000;
  92        } else
  93                msr_lo &= 0x0bc00000;
  94        msr_lo >>= 22;
  95        while (msr_lo != msr_decode_mult[j].bitmap) {
  96                if (msr_decode_mult[j].bitmap == 0xff)
  97                        return 0;
  98                j++;
  99        }
 100
 101        pr_debug("speed is %u\n",
 102                (msr_decode_mult[j].ratio * msr_decode_fsb[i].value * 100));
 103
 104        return msr_decode_mult[j].ratio * msr_decode_fsb[i].value * 100;
 105}
 106
 107
 108static unsigned int pentiumM_get_frequency(void)
 109{
 110        u32 msr_lo, msr_tmp;
 111
 112        rdmsr(MSR_IA32_EBL_CR_POWERON, msr_lo, msr_tmp);
 113        pr_debug("PM - MSR_IA32_EBL_CR_POWERON: 0x%x 0x%x\n", msr_lo, msr_tmp);
 114
 115        /* see table B-2 of 24547212.pdf */
 116        if (msr_lo & 0x00040000) {
 117                printk(KERN_DEBUG PFX "PM - invalid FSB: 0x%x 0x%x\n",
 118                                msr_lo, msr_tmp);
 119                return 0;
 120        }
 121
 122        msr_tmp = (msr_lo >> 22) & 0x1f;
 123        pr_debug("bits 22-26 are 0x%x, speed is %u\n",
 124                        msr_tmp, (msr_tmp * 100 * 1000));
 125
 126        return msr_tmp * 100 * 1000;
 127}
 128
 129static unsigned int pentium_core_get_frequency(void)
 130{
 131        u32 fsb = 0;
 132        u32 msr_lo, msr_tmp;
 133        int ret;
 134
 135        rdmsr(MSR_FSB_FREQ, msr_lo, msr_tmp);
 136        /* see table B-2 of 25366920.pdf */
 137        switch (msr_lo & 0x07) {
 138        case 5:
 139                fsb = 100000;
 140                break;
 141        case 1:
 142                fsb = 133333;
 143                break;
 144        case 3:
 145                fsb = 166667;
 146                break;
 147        case 2:
 148                fsb = 200000;
 149                break;
 150        case 0:
 151                fsb = 266667;
 152                break;
 153        case 4:
 154                fsb = 333333;
 155                break;
 156        default:
 157                pr_err("PCORE - MSR_FSB_FREQ undefined value\n");
 158        }
 159
 160        rdmsr(MSR_IA32_EBL_CR_POWERON, msr_lo, msr_tmp);
 161        pr_debug("PCORE - MSR_IA32_EBL_CR_POWERON: 0x%x 0x%x\n",
 162                        msr_lo, msr_tmp);
 163
 164        msr_tmp = (msr_lo >> 22) & 0x1f;
 165        pr_debug("bits 22-26 are 0x%x, speed is %u\n",
 166                        msr_tmp, (msr_tmp * fsb));
 167
 168        ret = (msr_tmp * fsb);
 169        return ret;
 170}
 171
 172
 173static unsigned int pentium4_get_frequency(void)
 174{
 175        struct cpuinfo_x86 *c = &boot_cpu_data;
 176        u32 msr_lo, msr_hi, mult;
 177        unsigned int fsb = 0;
 178        unsigned int ret;
 179        u8 fsb_code;
 180
 181        /* Pentium 4 Model 0 and 1 do not have the Core Clock Frequency
 182         * to System Bus Frequency Ratio Field in the Processor Frequency
 183         * Configuration Register of the MSR. Therefore the current
 184         * frequency cannot be calculated and has to be measured.
 185         */
 186        if (c->x86_model < 2)
 187                return cpu_khz;
 188
 189        rdmsr(0x2c, msr_lo, msr_hi);
 190
 191        pr_debug("P4 - MSR_EBC_FREQUENCY_ID: 0x%x 0x%x\n", msr_lo, msr_hi);
 192
 193        /* decode the FSB: see IA-32 Intel (C) Architecture Software
 194         * Developer's Manual, Volume 3: System Prgramming Guide,
 195         * revision #12 in Table B-1: MSRs in the Pentium 4 and
 196         * Intel Xeon Processors, on page B-4 and B-5.
 197         */
 198        fsb_code = (msr_lo >> 16) & 0x7;
 199        switch (fsb_code) {
 200        case 0:
 201                fsb = 100 * 1000;
 202                break;
 203        case 1:
 204                fsb = 13333 * 10;
 205                break;
 206        case 2:
 207                fsb = 200 * 1000;
 208                break;
 209        }
 210
 211        if (!fsb)
 212                printk(KERN_DEBUG PFX "couldn't detect FSB speed. "
 213                                "Please send an e-mail to <linux@brodo.de>\n");
 214
 215        /* Multiplier. */
 216        mult = msr_lo >> 24;
 217
 218        pr_debug("P4 - FSB %u kHz; Multiplier %u; Speed %u kHz\n",
 219                        fsb, mult, (fsb * mult));
 220
 221        ret = (fsb * mult);
 222        return ret;
 223}
 224
 225
 226/* Warning: may get called from smp_call_function_single. */
 227unsigned int speedstep_get_frequency(enum speedstep_processor processor)
 228{
 229        switch (processor) {
 230        case SPEEDSTEP_CPU_PCORE:
 231                return pentium_core_get_frequency();
 232        case SPEEDSTEP_CPU_PM:
 233                return pentiumM_get_frequency();
 234        case SPEEDSTEP_CPU_P4D:
 235        case SPEEDSTEP_CPU_P4M:
 236                return pentium4_get_frequency();
 237        case SPEEDSTEP_CPU_PIII_T:
 238        case SPEEDSTEP_CPU_PIII_C:
 239        case SPEEDSTEP_CPU_PIII_C_EARLY:
 240                return pentium3_get_frequency(processor);
 241        default:
 242                return 0;
 243        }
 244        return 0;
 245}
 246EXPORT_SYMBOL_GPL(speedstep_get_frequency);
 247
 248
 249/*********************************************************************
 250 *                 DETECT SPEEDSTEP-CAPABLE PROCESSOR                *
 251 *********************************************************************/
 252
 253/* Keep in sync with the x86_cpu_id tables in the different modules */
 254enum speedstep_processor speedstep_detect_processor(void)
 255{
 256        struct cpuinfo_x86 *c = &cpu_data(0);
 257        u32 ebx, msr_lo, msr_hi;
 258
 259        pr_debug("x86: %x, model: %x\n", c->x86, c->x86_model);
 260
 261        if ((c->x86_vendor != X86_VENDOR_INTEL) ||
 262            ((c->x86 != 6) && (c->x86 != 0xF)))
 263                return 0;
 264
 265        if (c->x86 == 0xF) {
 266                /* Intel Mobile Pentium 4-M
 267                 * or Intel Mobile Pentium 4 with 533 MHz FSB */
 268                if (c->x86_model != 2)
 269                        return 0;
 270
 271                ebx = cpuid_ebx(0x00000001);
 272                ebx &= 0x000000FF;
 273
 274                pr_debug("ebx value is %x, x86_stepping is %x\n", ebx, c->x86_stepping);
 275
 276                switch (c->x86_stepping) {
 277                case 4:
 278                        /*
 279                         * B-stepping [M-P4-M]
 280                         * sample has ebx = 0x0f, production has 0x0e.
 281                         */
 282                        if ((ebx == 0x0e) || (ebx == 0x0f))
 283                                return SPEEDSTEP_CPU_P4M;
 284                        break;
 285                case 7:
 286                        /*
 287                         * C-stepping [M-P4-M]
 288                         * needs to have ebx=0x0e, else it's a celeron:
 289                         * cf. 25130917.pdf / page 7, footnote 5 even
 290                         * though 25072120.pdf / page 7 doesn't say
 291                         * samples are only of B-stepping...
 292                         */
 293                        if (ebx == 0x0e)
 294                                return SPEEDSTEP_CPU_P4M;
 295                        break;
 296                case 9:
 297                        /*
 298                         * D-stepping [M-P4-M or M-P4/533]
 299                         *
 300                         * this is totally strange: CPUID 0x0F29 is
 301                         * used by M-P4-M, M-P4/533 and(!) Celeron CPUs.
 302                         * The latter need to be sorted out as they don't
 303                         * support speedstep.
 304                         * Celerons with CPUID 0x0F29 may have either
 305                         * ebx=0x8 or 0xf -- 25130917.pdf doesn't say anything
 306                         * specific.
 307                         * M-P4-Ms may have either ebx=0xe or 0xf [see above]
 308                         * M-P4/533 have either ebx=0xe or 0xf. [25317607.pdf]
 309                         * also, M-P4M HTs have ebx=0x8, too
 310                         * For now, they are distinguished by the model_id
 311                         * string
 312                         */
 313                        if ((ebx == 0x0e) ||
 314                                (strstr(c->x86_model_id,
 315                                    "Mobile Intel(R) Pentium(R) 4") != NULL))
 316                                return SPEEDSTEP_CPU_P4M;
 317                        break;
 318                default:
 319                        break;
 320                }
 321                return 0;
 322        }
 323
 324        switch (c->x86_model) {
 325        case 0x0B: /* Intel PIII [Tualatin] */
 326                /* cpuid_ebx(1) is 0x04 for desktop PIII,
 327                 * 0x06 for mobile PIII-M */
 328                ebx = cpuid_ebx(0x00000001);
 329                pr_debug("ebx is %x\n", ebx);
 330
 331                ebx &= 0x000000FF;
 332
 333                if (ebx != 0x06)
 334                        return 0;
 335
 336                /* So far all PIII-M processors support SpeedStep. See
 337                 * Intel's 24540640.pdf of June 2003
 338                 */
 339                return SPEEDSTEP_CPU_PIII_T;
 340
 341        case 0x08: /* Intel PIII [Coppermine] */
 342
 343                /* all mobile PIII Coppermines have FSB 100 MHz
 344                 * ==> sort out a few desktop PIIIs. */
 345                rdmsr(MSR_IA32_EBL_CR_POWERON, msr_lo, msr_hi);
 346                pr_debug("Coppermine: MSR_IA32_EBL_CR_POWERON is 0x%x, 0x%x\n",
 347                                msr_lo, msr_hi);
 348                msr_lo &= 0x00c0000;
 349                if (msr_lo != 0x0080000)
 350                        return 0;
 351
 352                /*
 353                 * If the processor is a mobile version,
 354                 * platform ID has bit 50 set
 355                 * it has SpeedStep technology if either
 356                 * bit 56 or 57 is set
 357                 */
 358                rdmsr(MSR_IA32_PLATFORM_ID, msr_lo, msr_hi);
 359                pr_debug("Coppermine: MSR_IA32_PLATFORM ID is 0x%x, 0x%x\n",
 360                                msr_lo, msr_hi);
 361                if ((msr_hi & (1<<18)) &&
 362                    (relaxed_check ? 1 : (msr_hi & (3<<24)))) {
 363                        if (c->x86_stepping == 0x01) {
 364                                pr_debug("early PIII version\n");
 365                                return SPEEDSTEP_CPU_PIII_C_EARLY;
 366                        } else
 367                                return SPEEDSTEP_CPU_PIII_C;
 368                }
 369                fallthrough;
 370        default:
 371                return 0;
 372        }
 373}
 374EXPORT_SYMBOL_GPL(speedstep_detect_processor);
 375
 376
 377/*********************************************************************
 378 *                     DETECT SPEEDSTEP SPEEDS                       *
 379 *********************************************************************/
 380
 381unsigned int speedstep_get_freqs(enum speedstep_processor processor,
 382                                  unsigned int *low_speed,
 383                                  unsigned int *high_speed,
 384                                  unsigned int *transition_latency,
 385                                  void (*set_state) (unsigned int state))
 386{
 387        unsigned int prev_speed;
 388        unsigned int ret = 0;
 389        unsigned long flags;
 390        ktime_t tv1, tv2;
 391
 392        if ((!processor) || (!low_speed) || (!high_speed) || (!set_state))
 393                return -EINVAL;
 394
 395        pr_debug("trying to determine both speeds\n");
 396
 397        /* get current speed */
 398        prev_speed = speedstep_get_frequency(processor);
 399        if (!prev_speed)
 400                return -EIO;
 401
 402        pr_debug("previous speed is %u\n", prev_speed);
 403
 404        preempt_disable();
 405        local_irq_save(flags);
 406
 407        /* switch to low state */
 408        set_state(SPEEDSTEP_LOW);
 409        *low_speed = speedstep_get_frequency(processor);
 410        if (!*low_speed) {
 411                ret = -EIO;
 412                goto out;
 413        }
 414
 415        pr_debug("low speed is %u\n", *low_speed);
 416
 417        /* start latency measurement */
 418        if (transition_latency)
 419                tv1 = ktime_get();
 420
 421        /* switch to high state */
 422        set_state(SPEEDSTEP_HIGH);
 423
 424        /* end latency measurement */
 425        if (transition_latency)
 426                tv2 = ktime_get();
 427
 428        *high_speed = speedstep_get_frequency(processor);
 429        if (!*high_speed) {
 430                ret = -EIO;
 431                goto out;
 432        }
 433
 434        pr_debug("high speed is %u\n", *high_speed);
 435
 436        if (*low_speed == *high_speed) {
 437                ret = -ENODEV;
 438                goto out;
 439        }
 440
 441        /* switch to previous state, if necessary */
 442        if (*high_speed != prev_speed)
 443                set_state(SPEEDSTEP_LOW);
 444
 445        if (transition_latency) {
 446                *transition_latency = ktime_to_us(ktime_sub(tv2, tv1));
 447                pr_debug("transition latency is %u uSec\n", *transition_latency);
 448
 449                /* convert uSec to nSec and add 20% for safety reasons */
 450                *transition_latency *= 1200;
 451
 452                /* check if the latency measurement is too high or too low
 453                 * and set it to a safe value (500uSec) in that case
 454                 */
 455                if (*transition_latency > 10000000 ||
 456                    *transition_latency < 50000) {
 457                        pr_warn("frequency transition measured seems out of range (%u nSec), falling back to a safe one of %u nSec\n",
 458                                *transition_latency, 500000);
 459                        *transition_latency = 500000;
 460                }
 461        }
 462
 463out:
 464        local_irq_restore(flags);
 465        preempt_enable();
 466
 467        return ret;
 468}
 469EXPORT_SYMBOL_GPL(speedstep_get_freqs);
 470
 471#ifdef CONFIG_X86_SPEEDSTEP_RELAXED_CAP_CHECK
 472module_param(relaxed_check, int, 0444);
 473MODULE_PARM_DESC(relaxed_check,
 474                "Don't do all checks for speedstep capability.");
 475#endif
 476
 477MODULE_AUTHOR("Dominik Brodowski <linux@brodo.de>");
 478MODULE_DESCRIPTION("Library for Intel SpeedStep 1 or 2 cpufreq drivers.");
 479MODULE_LICENSE("GPL");
 480