arch/i386/kernel/cpu/cpufreq/powernow-k7.c

   1 /*
   2  *  AMD K7 Powernow driver.
   3  *  (C) 2003 Dave Jones <davej@codemonkey.org.uk> on behalf of SuSE Labs.
   4  *  (C) 2003-2004 Dave Jones <davej@redhat.com>
   5  *
   6  *  Licensed under the terms of the GNU GPL License version 2.
   7  *  Based upon datasheets & sample CPUs kindly provided by AMD.
   8  *
   9  * Errata 5: Processor may fail to execute a FID/VID change in presence of interrupt.
  10  * - We cli/sti on stepping A0 CPUs around the FID/VID transition.
  11  * Errata 15: Processors with half frequency multipliers may hang upon wakeup from disconnect.
  12  * - We disable half multipliers if ACPI is used on A0 stepping CPUs.
  13  */
  14
  15 #include <linux/kernel.h>
  16 #include <linux/module.h>
  17 #include <linux/moduleparam.h>
  18 #include <linux/init.h>
  19 #include <linux/cpufreq.h>
  20 #include <linux/slab.h>
  21 #include <linux/string.h>
  22 #include <linux/dmi.h>
  23
  24 #include <asm/msr.h>
  25 #include <asm/timer.h>
  26 #include <asm/timex.h>
  27 #include <asm/io.h>
  28 #include <asm/system.h>
  29
  30 #ifdef CONFIG_X86_POWERNOW_K7_ACPI
  31 #include <linux/acpi.h>
  32 #include <acpi/processor.h>
  33 #endif
  34
  35 #include "powernow-k7.h"
  36
  37 #define PFX "powernow: "
  38
  39
  40 struct psb_s {
  41         u8 signature[10];
  42         u8 tableversion;
  43         u8 flags;
  44         u16 settlingtime;
  45         u8 reserved1;
  46         u8 numpst;
  47 };
  48
  49 struct pst_s {
  50         u32 cpuid;
  51         u8 fsbspeed;
  52         u8 maxfid;
  53         u8 startvid;
  54         u8 numpstates;
  55 };
  56
  57 #ifdef CONFIG_X86_POWERNOW_K7_ACPI
  58 union powernow_acpi_control_t {
  59         struct {
  60                 unsigned long fid:5,
  61                 vid:5,
  62                 sgtc:20,
  63                 res1:2;
  64         } bits;
  65         unsigned long val;
  66 };
  67 #endif
  68
  69 #ifdef CONFIG_CPU_FREQ_DEBUG
  70 /* divide by 1000 to get VCore voltage in V. */
  71 static const int mobile_vid_table[32] = {
  72     2000, 1950, 1900, 1850, 1800, 1750, 1700, 1650,
  73     1600, 1550, 1500, 1450, 1400, 1350, 1300, 0,
  74     1275, 1250, 1225, 1200, 1175, 1150, 1125, 1100,
  75     1075, 1050, 1025, 1000, 975, 950, 925, 0,
  76 };
  77 #endif
  78
  79 /* divide by 10 to get FID. */
  80 static const int fid_codes[32] = {
  81     110, 115, 120, 125, 50, 55, 60, 65,
  82     70, 75, 80, 85, 90, 95, 100, 105,
  83     30, 190, 40, 200, 130, 135, 140, 210,
  84     150, 225, 160, 165, 170, 180, -1, -1,
  85 };
  86
  87 /* This parameter is used in order to force ACPI instead of legacy method for
  88  * configuration purpose.
  89  */
  90
  91 static int acpi_force;
  92
  93 static struct cpufreq_frequency_table *powernow_table;
  94
  95 static unsigned int can_scale_bus;
  96 static unsigned int can_scale_vid;
  97 static unsigned int minimum_speed=-1;
  98 static unsigned int maximum_speed;
  99 static unsigned int number_scales;
 100 static unsigned int fsb;
 101 static unsigned int latency;
 102 static char have_a0;
 103
 104 #define dprintk(msg...) cpufreq_debug_printk(CPUFREQ_DEBUG_DRIVER, "powernow-k7", msg)
 105
 106 static int check_fsb(unsigned int fsbspeed)
 107 {
 108         int delta;
 109         unsigned int f = fsb / 1000;
 110
 111         delta = (fsbspeed > f) ? fsbspeed - f : f - fsbspeed;
 112         return (delta < 5);
 113 }
 114
 115 static int check_powernow(void)
 116 {
 117         struct cpuinfo_x86 *c = cpu_data;
 118         unsigned int maxei, eax, ebx, ecx, edx;
 119
 120         if ((c->x86_vendor != X86_VENDOR_AMD) || (c->x86 !=6)) {
 121 #ifdef MODULE
 122                 printk (KERN_INFO PFX "This module only works with AMD K7 CPUs\n");
 123 #endif
 124                 return 0;
 125         }
 126
 127         /* Get maximum capabilities */
 128         maxei = cpuid_eax (0x80000000);
 129         if (maxei < 0x80000007) {       /* Any powernow info ? */
 130 #ifdef MODULE
 131                 printk (KERN_INFO PFX "No powernow capabilities detected\n");
 132 #endif
 133                 return 0;
 134         }
 135
 136         if ((c->x86_model == 6) && (c->x86_mask == 0)) {
 137                 printk (KERN_INFO PFX "K7 660[A0] core detected, enabling errata workarounds\n");
 138                 have_a0 = 1;
 139         }
 140
 141         cpuid(0x80000007, &eax, &ebx, &ecx, &edx);
 142
 143         /* Check we can actually do something before we say anything.*/
 144         if (!(edx & (1 << 1 | 1 << 2)))
 145                 return 0;
 146
 147         printk (KERN_INFO PFX "PowerNOW! Technology present. Can scale: ");
 148
 149         if (edx & 1 << 1) {
 150                 printk ("frequency");
 151                 can_scale_bus=1;
 152         }
 153
 154         if ((edx & (1 << 1 | 1 << 2)) == 0x6)
 155                 printk (" and ");
 156
 157         if (edx & 1 << 2) {
 158                 printk ("voltage");
 159                 can_scale_vid=1;
 160         }
 161
 162         printk (".\n");
 163         return 1;
 164 }
 165
 166
 167 static int get_ranges (unsigned char *pst)
 168 {
 169         unsigned int j;
 170         unsigned int speed;
 171         u8 fid, vid;
 172
 173         powernow_table = kzalloc((sizeof(struct cpufreq_frequency_table) * (number_scales + 1)), GFP_KERNEL);
 174         if (!powernow_table)
 175                 return -ENOMEM;
 176
 177         for (j=0 ; j < number_scales; j++) {
 178                 fid = *pst++;
 179
 180                 powernow_table[j].frequency = (fsb * fid_codes[fid]) / 10;
 181                 powernow_table[j].index = fid; /* lower 8 bits */
 182
 183                 speed = powernow_table[j].frequency;
 184
 185                 if ((fid_codes[fid] % 10)==5) {
 186 #ifdef CONFIG_X86_POWERNOW_K7_ACPI
 187                         if (have_a0 == 1)
 188                                 powernow_table[j].frequency = CPUFREQ_ENTRY_INVALID;
 189 #endif
 190                 }
 191
 192                 if (speed < minimum_speed)
 193                         minimum_speed = speed;
 194                 if (speed > maximum_speed)
 195                         maximum_speed = speed;
 196
 197                 vid = *pst++;
 198                 powernow_table[j].index |= (vid << 8); /* upper 8 bits */
 199
 200                 dprintk ("   FID: 0x%x (%d.%dx [%dMHz])  "
 201                          "VID: 0x%x (%d.%03dV)\n", fid, fid_codes[fid] / 10,
 202                          fid_codes[fid] % 10, speed/1000, vid,
 203                          mobile_vid_table[vid]/1000,
 204                          mobile_vid_table[vid]%1000);
 205         }
 206         powernow_table[number_scales].frequency = CPUFREQ_TABLE_END;
 207         powernow_table[number_scales].index = 0;
 208
 209         return 0;
 210 }
 211
 212
 213 static void change_FID(int fid)
 214 {
 215         union msr_fidvidctl fidvidctl;
 216
 217         rdmsrl (MSR_K7_FID_VID_CTL, fidvidctl.val);
 218         if (fidvidctl.bits.FID != fid) {
 219                 fidvidctl.bits.SGTC = latency;
 220                 fidvidctl.bits.FID = fid;
 221                 fidvidctl.bits.VIDC = 0;
 222                 fidvidctl.bits.FIDC = 1;
 223                 wrmsrl (MSR_K7_FID_VID_CTL, fidvidctl.val);
 224         }
 225 }
 226
 227
 228 static void change_VID(int vid)
 229 {
 230         union msr_fidvidctl fidvidctl;
 231
 232         rdmsrl (MSR_K7_FID_VID_CTL, fidvidctl.val);
 233         if (fidvidctl.bits.VID != vid) {
 234                 fidvidctl.bits.SGTC = latency;
 235                 fidvidctl.bits.VID = vid;
 236                 fidvidctl.bits.FIDC = 0;
 237                 fidvidctl.bits.VIDC = 1;
 238                 wrmsrl (MSR_K7_FID_VID_CTL, fidvidctl.val);
 239         }
 240 }
 241
 242
 243 static void change_speed (unsigned int index)
 244 {
 245         u8 fid, vid;
 246         struct cpufreq_freqs freqs;
 247         union msr_fidvidstatus fidvidstatus;
 248         int cfid;
 249
 250         /* fid are the lower 8 bits of the index we stored into
 251          * the cpufreq frequency table in powernow_decode_bios,
 252          * vid are the upper 8 bits.
 253          */
 254
 255         fid = powernow_table[index].index & 0xFF;
 256         vid = (powernow_table[index].index & 0xFF00) >> 8;
 257
 258         freqs.cpu = 0;
 259
 260         rdmsrl (MSR_K7_FID_VID_STATUS, fidvidstatus.val);
 261         cfid = fidvidstatus.bits.CFID;
 262         freqs.old = fsb * fid_codes[cfid] / 10;
 263
 264         freqs.new = powernow_table[index].frequency;
 265
 266         cpufreq_notify_transition(&freqs, CPUFREQ_PRECHANGE);
 267
 268         /* Now do the magic poking into the MSRs.  */
 269
 270         if (have_a0 == 1)       /* A0 errata 5 */
 271                 local_irq_disable();
 272
 273         if (freqs.old > freqs.new) {
 274                 /* Going down, so change FID first */
 275                 change_FID(fid);
 276                 change_VID(vid);
 277         } else {
 278                 /* Going up, so change VID first */
 279                 change_VID(vid);
 280                 change_FID(fid);
 281         }
 282
 283
 284         if (have_a0 == 1)
 285                 local_irq_enable();
 286
 287         cpufreq_notify_transition(&freqs, CPUFREQ_POSTCHANGE);
 288 }
 289
 290
 291 #ifdef CONFIG_X86_POWERNOW_K7_ACPI
 292
 293 static struct acpi_processor_performance *acpi_processor_perf;
 294
 295 static int powernow_acpi_init(void)
 296 {
 297         int i;
 298         int retval = 0;
 299         union powernow_acpi_control_t pc;
 300
 301         if (acpi_processor_perf != NULL && powernow_table != NULL) {
 302                 retval = -EINVAL;
 303                 goto err0;
 304         }
 305
 306         acpi_processor_perf = kzalloc(sizeof(struct acpi_processor_performance),
 307                                       GFP_KERNEL);
 308         if (!acpi_processor_perf) {
 309                 retval = -ENOMEM;
 310                 goto err0;
 311         }
 312
 313         if (acpi_processor_register_performance(acpi_processor_perf, 0)) {
 314                 retval = -EIO;
 315                 goto err1;
 316         }
 317
 318         if (acpi_processor_perf->control_register.space_id != ACPI_ADR_SPACE_FIXED_HARDWARE) {
 319                 retval = -ENODEV;
 320                 goto err2;
 321         }
 322
 323         if (acpi_processor_perf->status_register.space_id != ACPI_ADR_SPACE_FIXED_HARDWARE) {
 324                 retval = -ENODEV;
 325                 goto err2;
 326         }
 327
 328         number_scales = acpi_processor_perf->state_count;
 329
 330         if (number_scales < 2) {
 331                 retval = -ENODEV;
 332                 goto err2;
 333         }
 334
 335         powernow_table = kzalloc((number_scales + 1) * (sizeof(struct cpufreq_frequency_table)), GFP_KERNEL);
 336         if (!powernow_table) {
 337                 retval = -ENOMEM;
 338                 goto err2;
 339         }
 340
 341         pc.val = (unsigned long) acpi_processor_perf->states[0].control;
 342         for (i = 0; i < number_scales; i++) {
 343                 u8 fid, vid;
 344                 unsigned int speed;
 345
 346                 pc.val = (unsigned long) acpi_processor_perf->states[i].control;
 347                 dprintk ("acpi:  P%d: %d MHz %d mW %d uS control %08x SGTC %d\n",
 348                          i,
 349                          (u32) acpi_processor_perf->states[i].core_frequency,
 350                          (u32) acpi_processor_perf->states[i].power,
 351                          (u32) acpi_processor_perf->states[i].transition_latency,
 352                          (u32) acpi_processor_perf->states[i].control,
 353                          pc.bits.sgtc);
 354
 355                 vid = pc.bits.vid;
 356                 fid = pc.bits.fid;
 357
 358                 powernow_table[i].frequency = fsb * fid_codes[fid] / 10;
 359                 powernow_table[i].index = fid; /* lower 8 bits */
 360                 powernow_table[i].index |= (vid << 8); /* upper 8 bits */
 361
 362                 speed = powernow_table[i].frequency;
 363
 364                 if ((fid_codes[fid] % 10)==5) {
 365                         if (have_a0 == 1)
 366                                 powernow_table[i].frequency = CPUFREQ_ENTRY_INVALID;
 367                 }
 368
 369                 dprintk ("   FID: 0x%x (%d.%dx [%dMHz])  "
 370                          "VID: 0x%x (%d.%03dV)\n", fid, fid_codes[fid] / 10,
 371                          fid_codes[fid] % 10, speed/1000, vid,
 372                          mobile_vid_table[vid]/1000,
 373                          mobile_vid_table[vid]%1000);
 374
 375                 if (latency < pc.bits.sgtc)
 376                         latency = pc.bits.sgtc;
 377
 378                 if (speed < minimum_speed)
 379                         minimum_speed = speed;
 380                 if (speed > maximum_speed)
 381                         maximum_speed = speed;
 382         }
 383
 384         powernow_table[i].frequency = CPUFREQ_TABLE_END;
 385         powernow_table[i].index = 0;
 386
 387         /* notify BIOS that we exist */
 388         acpi_processor_notify_smm(THIS_MODULE);
 389
 390         return 0;
 391
 392 err2:
 393         acpi_processor_unregister_performance(acpi_processor_perf, 0);
 394 err1:
 395         kfree(acpi_processor_perf);
 396 err0:
 397         printk(KERN_WARNING PFX "ACPI perflib can not be used in this platform\n");
 398         acpi_processor_perf = NULL;
 399         return retval;
 400 }
 401 #else
 402 static int powernow_acpi_init(void)
 403 {
 404         printk(KERN_INFO PFX "no support for ACPI processor found."
 405                "  Please recompile your kernel with ACPI processor\n");
 406         return -EINVAL;
 407 }
 408 #endif
 409
 410 static int powernow_decode_bios (int maxfid, int startvid)
 411 {
 412         struct psb_s *psb;
 413         struct pst_s *pst;
 414         unsigned int i, j;
 415         unsigned char *p;
 416         unsigned int etuple;
 417         unsigned int ret;
 418
 419         etuple = cpuid_eax(0x80000001);
 420
 421         for (i=0xC0000; i < 0xffff0 ; i+=16) {
 422
 423                 p = phys_to_virt(i);
 424
 425                 if (memcmp(p, "AMDK7PNOW!",  10) == 0){
 426                         dprintk ("Found PSB header at %p\n", p);
 427                         psb = (struct psb_s *) p;
 428                         dprintk ("Table version: 0x%x\n", psb->tableversion);
 429                         if (psb->tableversion != 0x12) {
 430                                 printk (KERN_INFO PFX "Sorry, only v1.2 tables supported right now\n");
 431                                 return -ENODEV;
 432                         }
 433
 434                         dprintk ("Flags: 0x%x\n", psb->flags);
 435                         if ((psb->flags & 1)==0) {
 436                                 dprintk ("Mobile voltage regulator\n");
 437                         } else {
 438                                 dprintk ("Desktop voltage regulator\n");
 439                         }
 440
 441                         latency = psb->settlingtime;
 442                         if (latency < 100) {
 443                                 printk (KERN_INFO PFX "BIOS set settling time to %d microseconds."
 444                                                 "Should be at least 100. Correcting.\n", latency);
 445                                 latency = 100;
 446                         }
 447                         dprintk ("Settling Time: %d microseconds.\n", psb->settlingtime);
 448                         dprintk ("Has %d PST tables. (Only dumping ones relevant to this CPU).\n", psb->numpst);
 449
 450                         p += sizeof (struct psb_s);
 451
 452                         pst = (struct pst_s *) p;
 453
 454                         for (j=0; j<psb->numpst; j++) {
 455                                 pst = (struct pst_s *) p;
 456                                 number_scales = pst->numpstates;
 457
 458                                 if ((etuple == pst->cpuid) && check_fsb(pst->fsbspeed) &&
 459                                     (maxfid==pst->maxfid) && (startvid==pst->startvid))
 460                                 {
 461                                         dprintk ("PST:%d (@%p)\n", j, pst);
 462                                         dprintk (" cpuid: 0x%x  fsb: %d  maxFID: 0x%x  startvid: 0x%x\n",
 463                                                  pst->cpuid, pst->fsbspeed, pst->maxfid, pst->startvid);
 464
 465                                         ret = get_ranges ((char *) pst + sizeof (struct pst_s));
 466                                         return ret;
 467                                 } else {
 468                                         unsigned int k;
 469                                         p = (char *) pst + sizeof (struct pst_s);
 470                                         for (k=0; k<number_scales; k++)
 471                                                 p+=2;
 472                                 }
 473                         }
 474                         printk (KERN_INFO PFX "No PST tables match this cpuid (0x%x)\n", etuple);
 475                         printk (KERN_INFO PFX "This is indicative of a broken BIOS.\n");
 476
 477                         return -EINVAL;
 478                 }
 479                 p++;
 480         }
 481
 482         return -ENODEV;
 483 }
 484
 485
 486 static int powernow_target (struct cpufreq_policy *policy,
 487                             unsigned int target_freq,
 488                             unsigned int relation)
 489 {
 490         unsigned int newstate;
 491
 492         if (cpufreq_frequency_table_target(policy, powernow_table, target_freq, relation, &newstate))
 493                 return -EINVAL;
 494
 495         change_speed(newstate);
 496
 497         return 0;
 498 }
 499
 500
 501 static int powernow_verify (struct cpufreq_policy *policy)
 502 {
 503         return cpufreq_frequency_table_verify(policy, powernow_table);
 504 }
 505
 506 /*
 507  * We use the fact that the bus frequency is somehow
 508  * a multiple of 100000/3 khz, then we compute sgtc according
 509  * to this multiple.
 510  * That way, we match more how AMD thinks all of that work.
 511  * We will then get the same kind of behaviour already tested under
 512  * the "well-known" other OS.
 513  */
 514 static int __init fixup_sgtc(void)
 515 {
 516         unsigned int sgtc;
 517         unsigned int m;
 518
 519         m = fsb / 3333;
 520         if ((m % 10) >= 5)
 521                 m += 5;
 522
 523         m /= 10;
 524
 525         sgtc = 100 * m * latency;
 526         sgtc = sgtc / 3;
 527         if (sgtc > 0xfffff) {
 528                 printk(KERN_WARNING PFX "SGTC too large %d\n", sgtc);
 529                 sgtc = 0xfffff;
 530         }
 531         return sgtc;
 532 }
 533
 534 static unsigned int powernow_get(unsigned int cpu)
 535 {
 536         union msr_fidvidstatus fidvidstatus;
 537         unsigned int cfid;
 538
 539         if (cpu)
 540                 return 0;
 541         rdmsrl (MSR_K7_FID_VID_STATUS, fidvidstatus.val);
 542         cfid = fidvidstatus.bits.CFID;
 543
 544         return (fsb * fid_codes[cfid] / 10);
 545 }
 546
 547
 548 static int __init acer_cpufreq_pst(struct dmi_system_id *d)
 549 {
 550         printk(KERN_WARNING "%s laptop with broken PST tables in BIOS detected.\n", d->ident);
 551         printk(KERN_WARNING "You need to downgrade to 3A21 (09/09/2002), or try a newer BIOS than 3A71 (01/20/2003)\n");
 552         printk(KERN_WARNING "cpufreq scaling has been disabled as a result of this.\n");
 553         return 0;
 554 }
 555
 556 /*
 557  * Some Athlon laptops have really fucked PST tables.
 558  * A BIOS update is all that can save them.
 559  * Mention this, and disable cpufreq.
 560  */
 561 static struct dmi_system_id __initdata powernow_dmi_table[] = {
 562         {
 563                 .callback = acer_cpufreq_pst,
 564                 .ident = "Acer Aspire",
 565                 .matches = {
 566                         DMI_MATCH(DMI_SYS_VENDOR, "Insyde Software"),
 567                         DMI_MATCH(DMI_BIOS_VERSION, "3A71"),
 568                 },
 569         },
 570         { }
 571 };
 572
 573 static int __init powernow_cpu_init (struct cpufreq_policy *policy)
 574 {
 575         union msr_fidvidstatus fidvidstatus;
 576         int result;
 577
 578         if (policy->cpu != 0)
 579                 return -ENODEV;
 580
 581         rdmsrl (MSR_K7_FID_VID_STATUS, fidvidstatus.val);
 582
 583         recalibrate_cpu_khz();
 584
 585         fsb = (10 * cpu_khz) / fid_codes[fidvidstatus.bits.CFID];
 586         if (!fsb) {
 587                 printk(KERN_WARNING PFX "can not determine bus frequency\n");
 588                 return -EINVAL;
 589         }
 590         dprintk("FSB: %3dMHz\n", fsb/1000);
 591
 592         if (dmi_check_system(powernow_dmi_table) || acpi_force) {
 593                 printk (KERN_INFO PFX "PSB/PST known to be broken.  Trying ACPI instead\n");
 594                 result = powernow_acpi_init();
 595         } else {
 596                 result = powernow_decode_bios(fidvidstatus.bits.MFID, fidvidstatus.bits.SVID);
 597                 if (result) {
 598                         printk (KERN_INFO PFX "Trying ACPI perflib\n");
 599                         maximum_speed = 0;
 600                         minimum_speed = -1;
 601                         latency = 0;
 602                         result = powernow_acpi_init();
 603                         if (result) {
 604                                 printk (KERN_INFO PFX "ACPI and legacy methods failed\n");
 605                                 printk (KERN_INFO PFX "See http://www.codemonkey.org.uk/projects/cpufreq/powernow-k7.shtml\n");
 606                         }
 607                 } else {
 608                         /* SGTC use the bus clock as timer */
 609                         latency = fixup_sgtc();
 610                         printk(KERN_INFO PFX "SGTC: %d\n", latency);
 611                 }
 612         }
 613
 614         if (result)
 615                 return result;
 616
 617         printk (KERN_INFO PFX "Minimum speed %d MHz. Maximum speed %d MHz.\n",
 618                                 minimum_speed/1000, maximum_speed/1000);
 619
 620         policy->governor = CPUFREQ_DEFAULT_GOVERNOR;
 621
 622         policy->cpuinfo.transition_latency = cpufreq_scale(2000000UL, fsb, latency);
 623
 624         policy->cur = powernow_get(0);
 625
 626         cpufreq_frequency_table_get_attr(powernow_table, policy->cpu);
 627
 628         return cpufreq_frequency_table_cpuinfo(policy, powernow_table);
 629 }
 630
 631 static int powernow_cpu_exit (struct cpufreq_policy *policy) {
 632         cpufreq_frequency_table_put_attr(policy->cpu);
 633
 634 #ifdef CONFIG_X86_POWERNOW_K7_ACPI
 635         if (acpi_processor_perf) {
 636                 acpi_processor_unregister_performance(acpi_processor_perf, 0);
 637                 kfree(acpi_processor_perf);
 638         }
 639 #endif
 640
 641         kfree(powernow_table);
 642         return 0;
 643 }
 644
 645 static struct freq_attr* powernow_table_attr[] = {
 646         &cpufreq_freq_attr_scaling_available_freqs,
 647         NULL,
 648 };
 649
 650 static struct cpufreq_driver powernow_driver = {
 651         .verify = powernow_verify,
 652         .target = powernow_target,
 653         .get    = powernow_get,
 654         .init   = powernow_cpu_init,
 655         .exit   = powernow_cpu_exit,
 656         .name   = "powernow-k7",
 657         .owner  = THIS_MODULE,
 658         .attr   = powernow_table_attr,
 659 };
 660
 661 static int __init powernow_init (void)
 662 {
 663         if (check_powernow()==0)
 664                 return -ENODEV;
 665         return cpufreq_register_driver(&powernow_driver);
 666 }
 667
 668
 669 static void __exit powernow_exit (void)
 670 {
 671         cpufreq_unregister_driver(&powernow_driver);
 672 }
 673
 674 module_param(acpi_force,  int, 0444);
 675 MODULE_PARM_DESC(acpi_force, "Force ACPI to be used.");
 676
 677 MODULE_AUTHOR ("Dave Jones <davej@codemonkey.org.uk>");
 678 MODULE_DESCRIPTION ("Powernow driver for AMD K7 processors.");
 679 MODULE_LICENSE ("GPL");
 680
 681 late_initcall(powernow_init);
 682 module_exit(powernow_exit);
 683