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
25 static int relaxed_check;
26 #else
27 #define relaxed_check 0
28 #endif
29 
30 /*********************************************************************
31  *                   GET PROCESSOR CORE SPEED IN KHZ                 *
32  *********************************************************************/
33 
34 static 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 
108 static 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 
129 static 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 
173 static 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. */
227 unsigned 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 }
246 EXPORT_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 */
254 enum 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 }
374 EXPORT_SYMBOL_GPL(speedstep_detect_processor);
375 
376 
377 /*********************************************************************
378  *                     DETECT SPEEDSTEP SPEEDS                       *
379  *********************************************************************/
380 
381 unsigned 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 
463 out:
464 	local_irq_restore(flags);
465 	preempt_enable();
466 
467 	return ret;
468 }
469 EXPORT_SYMBOL_GPL(speedstep_get_freqs);
470 
471 #ifdef CONFIG_X86_SPEEDSTEP_RELAXED_CAP_CHECK
472 module_param(relaxed_check, int, 0444);
473 MODULE_PARM_DESC(relaxed_check,
474 		"Don't do all checks for speedstep capability.");
475 #endif
476 
477 MODULE_AUTHOR("Dominik Brodowski <linux@brodo.de>");
478 MODULE_DESCRIPTION("Library for Intel SpeedStep 1 or 2 cpufreq drivers.");
479 MODULE_LICENSE("GPL");
480