xref: /openbmc/linux/drivers/cpufreq/powernow-k7.c (revision b11d77fa)
1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3  *  AMD K7 Powernow driver.
4  *  (C) 2003 Dave Jones on behalf of SuSE Labs.
5  *
6  *  Based upon datasheets & sample CPUs kindly provided by AMD.
7  *
8  * Errata 5:
9  *  CPU 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:
12  *  CPU with half frequency multipliers may hang upon wakeup from disconnect.
13  *  - We disable half multipliers if ACPI is used on A0 stepping CPUs.
14  */
15 
16 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
17 
18 #include <linux/kernel.h>
19 #include <linux/module.h>
20 #include <linux/moduleparam.h>
21 #include <linux/init.h>
22 #include <linux/cpufreq.h>
23 #include <linux/slab.h>
24 #include <linux/string.h>
25 #include <linux/dmi.h>
26 #include <linux/timex.h>
27 #include <linux/io.h>
28 
29 #include <asm/timer.h>		/* Needed for recalibrate_cpu_khz() */
30 #include <asm/msr.h>
31 #include <asm/cpu_device_id.h>
32 
33 #ifdef CONFIG_X86_POWERNOW_K7_ACPI
34 #include <linux/acpi.h>
35 #include <acpi/processor.h>
36 #endif
37 
38 #include "powernow-k7.h"
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 /* divide by 1000 to get VCore voltage in V. */
70 static const int mobile_vid_table[32] = {
71     2000, 1950, 1900, 1850, 1800, 1750, 1700, 1650,
72     1600, 1550, 1500, 1450, 1400, 1350, 1300, 0,
73     1275, 1250, 1225, 1200, 1175, 1150, 1125, 1100,
74     1075, 1050, 1025, 1000, 975, 950, 925, 0,
75 };
76 
77 /* divide by 10 to get FID. */
78 static const int fid_codes[32] = {
79     110, 115, 120, 125, 50, 55, 60, 65,
80     70, 75, 80, 85, 90, 95, 100, 105,
81     30, 190, 40, 200, 130, 135, 140, 210,
82     150, 225, 160, 165, 170, 180, -1, -1,
83 };
84 
85 /* This parameter is used in order to force ACPI instead of legacy method for
86  * configuration purpose.
87  */
88 
89 static int acpi_force;
90 
91 static struct cpufreq_frequency_table *powernow_table;
92 
93 static unsigned int can_scale_bus;
94 static unsigned int can_scale_vid;
95 static unsigned int minimum_speed = -1;
96 static unsigned int maximum_speed;
97 static unsigned int number_scales;
98 static unsigned int fsb;
99 static unsigned int latency;
100 static char have_a0;
101 
check_fsb(unsigned int fsbspeed)102 static int check_fsb(unsigned int fsbspeed)
103 {
104 	int delta;
105 	unsigned int f = fsb / 1000;
106 
107 	delta = (fsbspeed > f) ? fsbspeed - f : f - fsbspeed;
108 	return delta < 5;
109 }
110 
111 static const struct x86_cpu_id powernow_k7_cpuids[] = {
112 	X86_MATCH_VENDOR_FAM(AMD, 6, NULL),
113 	{}
114 };
115 MODULE_DEVICE_TABLE(x86cpu, powernow_k7_cpuids);
116 
check_powernow(void)117 static int check_powernow(void)
118 {
119 	struct cpuinfo_x86 *c = &cpu_data(0);
120 	unsigned int maxei, eax, ebx, ecx, edx;
121 
122 	if (!x86_match_cpu(powernow_k7_cpuids))
123 		return 0;
124 
125 	/* Get maximum capabilities */
126 	maxei = cpuid_eax(0x80000000);
127 	if (maxei < 0x80000007) {	/* Any powernow info ? */
128 #ifdef MODULE
129 		pr_info("No powernow capabilities detected\n");
130 #endif
131 		return 0;
132 	}
133 
134 	if ((c->x86_model == 6) && (c->x86_stepping == 0)) {
135 		pr_info("K7 660[A0] core detected, enabling errata workarounds\n");
136 		have_a0 = 1;
137 	}
138 
139 	cpuid(0x80000007, &eax, &ebx, &ecx, &edx);
140 
141 	/* Check we can actually do something before we say anything.*/
142 	if (!(edx & (1 << 1 | 1 << 2)))
143 		return 0;
144 
145 	pr_info("PowerNOW! Technology present. Can scale: ");
146 
147 	if (edx & 1 << 1) {
148 		pr_cont("frequency");
149 		can_scale_bus = 1;
150 	}
151 
152 	if ((edx & (1 << 1 | 1 << 2)) == 0x6)
153 		pr_cont(" and ");
154 
155 	if (edx & 1 << 2) {
156 		pr_cont("voltage");
157 		can_scale_vid = 1;
158 	}
159 
160 	pr_cont("\n");
161 	return 1;
162 }
163 
164 #ifdef CONFIG_X86_POWERNOW_K7_ACPI
invalidate_entry(unsigned int entry)165 static void invalidate_entry(unsigned int entry)
166 {
167 	powernow_table[entry].frequency = CPUFREQ_ENTRY_INVALID;
168 }
169 #endif
170 
get_ranges(unsigned char * pst)171 static int get_ranges(unsigned char *pst)
172 {
173 	unsigned int j;
174 	unsigned int speed;
175 	u8 fid, vid;
176 
177 	powernow_table = kzalloc((sizeof(*powernow_table) *
178 				(number_scales + 1)), GFP_KERNEL);
179 	if (!powernow_table)
180 		return -ENOMEM;
181 
182 	for (j = 0 ; j < number_scales; j++) {
183 		fid = *pst++;
184 
185 		powernow_table[j].frequency = (fsb * fid_codes[fid]) / 10;
186 		powernow_table[j].driver_data = fid; /* lower 8 bits */
187 
188 		speed = powernow_table[j].frequency;
189 
190 		if ((fid_codes[fid] % 10) == 5) {
191 #ifdef CONFIG_X86_POWERNOW_K7_ACPI
192 			if (have_a0 == 1)
193 				invalidate_entry(j);
194 #endif
195 		}
196 
197 		if (speed < minimum_speed)
198 			minimum_speed = speed;
199 		if (speed > maximum_speed)
200 			maximum_speed = speed;
201 
202 		vid = *pst++;
203 		powernow_table[j].driver_data |= (vid << 8); /* upper 8 bits */
204 
205 		pr_debug("   FID: 0x%x (%d.%dx [%dMHz])  "
206 			 "VID: 0x%x (%d.%03dV)\n", fid, fid_codes[fid] / 10,
207 			 fid_codes[fid] % 10, speed/1000, vid,
208 			 mobile_vid_table[vid]/1000,
209 			 mobile_vid_table[vid]%1000);
210 	}
211 	powernow_table[number_scales].frequency = CPUFREQ_TABLE_END;
212 	powernow_table[number_scales].driver_data = 0;
213 
214 	return 0;
215 }
216 
217 
change_FID(int fid)218 static void change_FID(int fid)
219 {
220 	union msr_fidvidctl fidvidctl;
221 
222 	rdmsrl(MSR_K7_FID_VID_CTL, fidvidctl.val);
223 	if (fidvidctl.bits.FID != fid) {
224 		fidvidctl.bits.SGTC = latency;
225 		fidvidctl.bits.FID = fid;
226 		fidvidctl.bits.VIDC = 0;
227 		fidvidctl.bits.FIDC = 1;
228 		wrmsrl(MSR_K7_FID_VID_CTL, fidvidctl.val);
229 	}
230 }
231 
232 
change_VID(int vid)233 static void change_VID(int vid)
234 {
235 	union msr_fidvidctl fidvidctl;
236 
237 	rdmsrl(MSR_K7_FID_VID_CTL, fidvidctl.val);
238 	if (fidvidctl.bits.VID != vid) {
239 		fidvidctl.bits.SGTC = latency;
240 		fidvidctl.bits.VID = vid;
241 		fidvidctl.bits.FIDC = 0;
242 		fidvidctl.bits.VIDC = 1;
243 		wrmsrl(MSR_K7_FID_VID_CTL, fidvidctl.val);
244 	}
245 }
246 
247 
powernow_target(struct cpufreq_policy * policy,unsigned int index)248 static int powernow_target(struct cpufreq_policy *policy, unsigned int index)
249 {
250 	u8 fid, vid;
251 	struct cpufreq_freqs freqs;
252 	union msr_fidvidstatus fidvidstatus;
253 	int cfid;
254 
255 	/* fid are the lower 8 bits of the index we stored into
256 	 * the cpufreq frequency table in powernow_decode_bios,
257 	 * vid are the upper 8 bits.
258 	 */
259 
260 	fid = powernow_table[index].driver_data & 0xFF;
261 	vid = (powernow_table[index].driver_data & 0xFF00) >> 8;
262 
263 	rdmsrl(MSR_K7_FID_VID_STATUS, fidvidstatus.val);
264 	cfid = fidvidstatus.bits.CFID;
265 	freqs.old = fsb * fid_codes[cfid] / 10;
266 
267 	freqs.new = powernow_table[index].frequency;
268 
269 	/* Now do the magic poking into the MSRs.  */
270 
271 	if (have_a0 == 1)	/* A0 errata 5 */
272 		local_irq_disable();
273 
274 	if (freqs.old > freqs.new) {
275 		/* Going down, so change FID first */
276 		change_FID(fid);
277 		change_VID(vid);
278 	} else {
279 		/* Going up, so change VID first */
280 		change_VID(vid);
281 		change_FID(fid);
282 	}
283 
284 
285 	if (have_a0 == 1)
286 		local_irq_enable();
287 
288 	return 0;
289 }
290 
291 
292 #ifdef CONFIG_X86_POWERNOW_K7_ACPI
293 
294 static struct acpi_processor_performance *acpi_processor_perf;
295 
powernow_acpi_init(void)296 static int powernow_acpi_init(void)
297 {
298 	int i;
299 	int retval = 0;
300 	union powernow_acpi_control_t pc;
301 
302 	if (acpi_processor_perf != NULL && powernow_table != NULL) {
303 		retval = -EINVAL;
304 		goto err0;
305 	}
306 
307 	acpi_processor_perf = kzalloc(sizeof(*acpi_processor_perf), GFP_KERNEL);
308 	if (!acpi_processor_perf) {
309 		retval = -ENOMEM;
310 		goto err0;
311 	}
312 
313 	if (!zalloc_cpumask_var(&acpi_processor_perf->shared_cpu_map,
314 								GFP_KERNEL)) {
315 		retval = -ENOMEM;
316 		goto err05;
317 	}
318 
319 	if (acpi_processor_register_performance(acpi_processor_perf, 0)) {
320 		retval = -EIO;
321 		goto err1;
322 	}
323 
324 	if (acpi_processor_perf->control_register.space_id !=
325 			ACPI_ADR_SPACE_FIXED_HARDWARE) {
326 		retval = -ENODEV;
327 		goto err2;
328 	}
329 
330 	if (acpi_processor_perf->status_register.space_id !=
331 			ACPI_ADR_SPACE_FIXED_HARDWARE) {
332 		retval = -ENODEV;
333 		goto err2;
334 	}
335 
336 	number_scales = acpi_processor_perf->state_count;
337 
338 	if (number_scales < 2) {
339 		retval = -ENODEV;
340 		goto err2;
341 	}
342 
343 	powernow_table = kzalloc((sizeof(*powernow_table) *
344 				(number_scales + 1)), GFP_KERNEL);
345 	if (!powernow_table) {
346 		retval = -ENOMEM;
347 		goto err2;
348 	}
349 
350 	pc.val = (unsigned long) acpi_processor_perf->states[0].control;
351 	for (i = 0; i < number_scales; i++) {
352 		u8 fid, vid;
353 		struct acpi_processor_px *state =
354 			&acpi_processor_perf->states[i];
355 		unsigned int speed, speed_mhz;
356 
357 		pc.val = (unsigned long) state->control;
358 		pr_debug("acpi:  P%d: %d MHz %d mW %d uS control %08x SGTC %d\n",
359 			 i,
360 			 (u32) state->core_frequency,
361 			 (u32) state->power,
362 			 (u32) state->transition_latency,
363 			 (u32) state->control,
364 			 pc.bits.sgtc);
365 
366 		vid = pc.bits.vid;
367 		fid = pc.bits.fid;
368 
369 		powernow_table[i].frequency = fsb * fid_codes[fid] / 10;
370 		powernow_table[i].driver_data = fid; /* lower 8 bits */
371 		powernow_table[i].driver_data |= (vid << 8); /* upper 8 bits */
372 
373 		speed = powernow_table[i].frequency;
374 		speed_mhz = speed / 1000;
375 
376 		/* processor_perflib will multiply the MHz value by 1000 to
377 		 * get a KHz value (e.g. 1266000). However, powernow-k7 works
378 		 * with true KHz values (e.g. 1266768). To ensure that all
379 		 * powernow frequencies are available, we must ensure that
380 		 * ACPI doesn't restrict them, so we round up the MHz value
381 		 * to ensure that perflib's computed KHz value is greater than
382 		 * or equal to powernow's KHz value.
383 		 */
384 		if (speed % 1000 > 0)
385 			speed_mhz++;
386 
387 		if ((fid_codes[fid] % 10) == 5) {
388 			if (have_a0 == 1)
389 				invalidate_entry(i);
390 		}
391 
392 		pr_debug("   FID: 0x%x (%d.%dx [%dMHz])  "
393 			 "VID: 0x%x (%d.%03dV)\n", fid, fid_codes[fid] / 10,
394 			 fid_codes[fid] % 10, speed_mhz, vid,
395 			 mobile_vid_table[vid]/1000,
396 			 mobile_vid_table[vid]%1000);
397 
398 		if (state->core_frequency != speed_mhz) {
399 			state->core_frequency = speed_mhz;
400 			pr_debug("   Corrected ACPI frequency to %d\n",
401 				speed_mhz);
402 		}
403 
404 		if (latency < pc.bits.sgtc)
405 			latency = pc.bits.sgtc;
406 
407 		if (speed < minimum_speed)
408 			minimum_speed = speed;
409 		if (speed > maximum_speed)
410 			maximum_speed = speed;
411 	}
412 
413 	powernow_table[i].frequency = CPUFREQ_TABLE_END;
414 	powernow_table[i].driver_data = 0;
415 
416 	/* notify BIOS that we exist */
417 	acpi_processor_notify_smm(THIS_MODULE);
418 
419 	return 0;
420 
421 err2:
422 	acpi_processor_unregister_performance(0);
423 err1:
424 	free_cpumask_var(acpi_processor_perf->shared_cpu_map);
425 err05:
426 	kfree(acpi_processor_perf);
427 err0:
428 	pr_warn("ACPI perflib can not be used on this platform\n");
429 	acpi_processor_perf = NULL;
430 	return retval;
431 }
432 #else
powernow_acpi_init(void)433 static int powernow_acpi_init(void)
434 {
435 	pr_info("no support for ACPI processor found - please recompile your kernel with ACPI processor\n");
436 	return -EINVAL;
437 }
438 #endif
439 
print_pst_entry(struct pst_s * pst,unsigned int j)440 static void print_pst_entry(struct pst_s *pst, unsigned int j)
441 {
442 	pr_debug("PST:%d (@%p)\n", j, pst);
443 	pr_debug(" cpuid: 0x%x  fsb: %d  maxFID: 0x%x  startvid: 0x%x\n",
444 		pst->cpuid, pst->fsbspeed, pst->maxfid, pst->startvid);
445 }
446 
powernow_decode_bios(int maxfid,int startvid)447 static int powernow_decode_bios(int maxfid, int startvid)
448 {
449 	struct psb_s *psb;
450 	struct pst_s *pst;
451 	unsigned int i, j;
452 	unsigned char *p;
453 	unsigned int etuple;
454 	unsigned int ret;
455 
456 	etuple = cpuid_eax(0x80000001);
457 
458 	for (i = 0xC0000; i < 0xffff0 ; i += 16) {
459 
460 		p = phys_to_virt(i);
461 
462 		if (memcmp(p, "AMDK7PNOW!",  10) == 0) {
463 			pr_debug("Found PSB header at %p\n", p);
464 			psb = (struct psb_s *) p;
465 			pr_debug("Table version: 0x%x\n", psb->tableversion);
466 			if (psb->tableversion != 0x12) {
467 				pr_info("Sorry, only v1.2 tables supported right now\n");
468 				return -ENODEV;
469 			}
470 
471 			pr_debug("Flags: 0x%x\n", psb->flags);
472 			if ((psb->flags & 1) == 0)
473 				pr_debug("Mobile voltage regulator\n");
474 			else
475 				pr_debug("Desktop voltage regulator\n");
476 
477 			latency = psb->settlingtime;
478 			if (latency < 100) {
479 				pr_info("BIOS set settling time to %d microseconds. Should be at least 100. Correcting.\n",
480 					latency);
481 				latency = 100;
482 			}
483 			pr_debug("Settling Time: %d microseconds.\n",
484 					psb->settlingtime);
485 			pr_debug("Has %d PST tables. (Only dumping ones "
486 					"relevant to this CPU).\n",
487 					psb->numpst);
488 
489 			p += sizeof(*psb);
490 
491 			pst = (struct pst_s *) p;
492 
493 			for (j = 0; j < psb->numpst; j++) {
494 				pst = (struct pst_s *) p;
495 				number_scales = pst->numpstates;
496 
497 				if ((etuple == pst->cpuid) &&
498 				    check_fsb(pst->fsbspeed) &&
499 				    (maxfid == pst->maxfid) &&
500 				    (startvid == pst->startvid)) {
501 					print_pst_entry(pst, j);
502 					p = (char *)pst + sizeof(*pst);
503 					ret = get_ranges(p);
504 					return ret;
505 				} else {
506 					unsigned int k;
507 					p = (char *)pst + sizeof(*pst);
508 					for (k = 0; k < number_scales; k++)
509 						p += 2;
510 				}
511 			}
512 			pr_info("No PST tables match this cpuid (0x%x)\n",
513 				etuple);
514 			pr_info("This is indicative of a broken BIOS\n");
515 
516 			return -EINVAL;
517 		}
518 		p++;
519 	}
520 
521 	return -ENODEV;
522 }
523 
524 
525 /*
526  * We use the fact that the bus frequency is somehow
527  * a multiple of 100000/3 khz, then we compute sgtc according
528  * to this multiple.
529  * That way, we match more how AMD thinks all of that work.
530  * We will then get the same kind of behaviour already tested under
531  * the "well-known" other OS.
532  */
fixup_sgtc(void)533 static int fixup_sgtc(void)
534 {
535 	unsigned int sgtc;
536 	unsigned int m;
537 
538 	m = fsb / 3333;
539 	if ((m % 10) >= 5)
540 		m += 5;
541 
542 	m /= 10;
543 
544 	sgtc = 100 * m * latency;
545 	sgtc = sgtc / 3;
546 	if (sgtc > 0xfffff) {
547 		pr_warn("SGTC too large %d\n", sgtc);
548 		sgtc = 0xfffff;
549 	}
550 	return sgtc;
551 }
552 
powernow_get(unsigned int cpu)553 static unsigned int powernow_get(unsigned int cpu)
554 {
555 	union msr_fidvidstatus fidvidstatus;
556 	unsigned int cfid;
557 
558 	if (cpu)
559 		return 0;
560 	rdmsrl(MSR_K7_FID_VID_STATUS, fidvidstatus.val);
561 	cfid = fidvidstatus.bits.CFID;
562 
563 	return fsb * fid_codes[cfid] / 10;
564 }
565 
566 
acer_cpufreq_pst(const struct dmi_system_id * d)567 static int acer_cpufreq_pst(const struct dmi_system_id *d)
568 {
569 	pr_warn("%s laptop with broken PST tables in BIOS detected\n",
570 		d->ident);
571 	pr_warn("You need to downgrade to 3A21 (09/09/2002), or try a newer BIOS than 3A71 (01/20/2003)\n");
572 	pr_warn("cpufreq scaling has been disabled as a result of this\n");
573 	return 0;
574 }
575 
576 /*
577  * Some Athlon laptops have really fucked PST tables.
578  * A BIOS update is all that can save them.
579  * Mention this, and disable cpufreq.
580  */
581 static const struct dmi_system_id powernow_dmi_table[] = {
582 	{
583 		.callback = acer_cpufreq_pst,
584 		.ident = "Acer Aspire",
585 		.matches = {
586 			DMI_MATCH(DMI_SYS_VENDOR, "Insyde Software"),
587 			DMI_MATCH(DMI_BIOS_VERSION, "3A71"),
588 		},
589 	},
590 	{ }
591 };
592 
powernow_cpu_init(struct cpufreq_policy * policy)593 static int powernow_cpu_init(struct cpufreq_policy *policy)
594 {
595 	union msr_fidvidstatus fidvidstatus;
596 	int result;
597 
598 	if (policy->cpu != 0)
599 		return -ENODEV;
600 
601 	rdmsrl(MSR_K7_FID_VID_STATUS, fidvidstatus.val);
602 
603 	recalibrate_cpu_khz();
604 
605 	fsb = (10 * cpu_khz) / fid_codes[fidvidstatus.bits.CFID];
606 	if (!fsb) {
607 		pr_warn("can not determine bus frequency\n");
608 		return -EINVAL;
609 	}
610 	pr_debug("FSB: %3dMHz\n", fsb/1000);
611 
612 	if (dmi_check_system(powernow_dmi_table) || acpi_force) {
613 		pr_info("PSB/PST known to be broken - trying ACPI instead\n");
614 		result = powernow_acpi_init();
615 	} else {
616 		result = powernow_decode_bios(fidvidstatus.bits.MFID,
617 				fidvidstatus.bits.SVID);
618 		if (result) {
619 			pr_info("Trying ACPI perflib\n");
620 			maximum_speed = 0;
621 			minimum_speed = -1;
622 			latency = 0;
623 			result = powernow_acpi_init();
624 			if (result) {
625 				pr_info("ACPI and legacy methods failed\n");
626 			}
627 		} else {
628 			/* SGTC use the bus clock as timer */
629 			latency = fixup_sgtc();
630 			pr_info("SGTC: %d\n", latency);
631 		}
632 	}
633 
634 	if (result)
635 		return result;
636 
637 	pr_info("Minimum speed %d MHz - Maximum speed %d MHz\n",
638 		minimum_speed/1000, maximum_speed/1000);
639 
640 	policy->cpuinfo.transition_latency =
641 		cpufreq_scale(2000000UL, fsb, latency);
642 	policy->freq_table = powernow_table;
643 
644 	return 0;
645 }
646 
powernow_cpu_exit(struct cpufreq_policy * policy)647 static int powernow_cpu_exit(struct cpufreq_policy *policy)
648 {
649 #ifdef CONFIG_X86_POWERNOW_K7_ACPI
650 	if (acpi_processor_perf) {
651 		acpi_processor_unregister_performance(0);
652 		free_cpumask_var(acpi_processor_perf->shared_cpu_map);
653 		kfree(acpi_processor_perf);
654 	}
655 #endif
656 
657 	kfree(powernow_table);
658 	return 0;
659 }
660 
661 static struct cpufreq_driver powernow_driver = {
662 	.verify		= cpufreq_generic_frequency_table_verify,
663 	.target_index	= powernow_target,
664 	.get		= powernow_get,
665 #ifdef CONFIG_X86_POWERNOW_K7_ACPI
666 	.bios_limit	= acpi_processor_get_bios_limit,
667 #endif
668 	.init		= powernow_cpu_init,
669 	.exit		= powernow_cpu_exit,
670 	.name		= "powernow-k7",
671 	.attr		= cpufreq_generic_attr,
672 };
673 
powernow_init(void)674 static int __init powernow_init(void)
675 {
676 	if (check_powernow() == 0)
677 		return -ENODEV;
678 	return cpufreq_register_driver(&powernow_driver);
679 }
680 
681 
powernow_exit(void)682 static void __exit powernow_exit(void)
683 {
684 	cpufreq_unregister_driver(&powernow_driver);
685 }
686 
687 module_param(acpi_force,  int, 0444);
688 MODULE_PARM_DESC(acpi_force, "Force ACPI to be used.");
689 
690 MODULE_AUTHOR("Dave Jones");
691 MODULE_DESCRIPTION("Powernow driver for AMD K7 processors.");
692 MODULE_LICENSE("GPL");
693 
694 late_initcall(powernow_init);
695 module_exit(powernow_exit);
696 
697