summaryrefslogtreecommitdiff
path: root/arch/x86/kernel/cpu/cpufreq/longrun.c
blob: fc09f142d94d964539e11e55101e5edaaf60eaac (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
/*
 * (C) 2002 - 2003  Dominik Brodowski <linux@brodo.de>
 *
 *  Licensed under the terms of the GNU GPL License version 2.
 *
 *  BIG FAT DISCLAIMER: Work in progress code. Possibly *dangerous*
 */

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/cpufreq.h>
#include <linux/timex.h>

#include <asm/msr.h>
#include <asm/processor.h>

#define dprintk(msg...) cpufreq_debug_printk(CPUFREQ_DEBUG_DRIVER, \
		"longrun", msg)

static struct cpufreq_driver	longrun_driver;

/**
 * longrun_{low,high}_freq is needed for the conversion of cpufreq kHz
 * values into per cent values. In TMTA microcode, the following is valid:
 * performance_pctg = (current_freq - low_freq)/(high_freq - low_freq)
 */
static unsigned int longrun_low_freq, longrun_high_freq;


/**
 * longrun_get_policy - get the current LongRun policy
 * @policy: struct cpufreq_policy where current policy is written into
 *
 * Reads the current LongRun policy by access to MSR_TMTA_LONGRUN_FLAGS
 * and MSR_TMTA_LONGRUN_CTRL
 */
static void __init longrun_get_policy(struct cpufreq_policy *policy)
{
	u32 msr_lo, msr_hi;

	rdmsr(MSR_TMTA_LONGRUN_FLAGS, msr_lo, msr_hi);
	dprintk("longrun flags are %x - %x\n", msr_lo, msr_hi);
	if (msr_lo & 0x01)
		policy->policy = CPUFREQ_POLICY_PERFORMANCE;
	else
		policy->policy = CPUFREQ_POLICY_POWERSAVE;

	rdmsr(MSR_TMTA_LONGRUN_CTRL, msr_lo, msr_hi);
	dprintk("longrun ctrl is %x - %x\n", msr_lo, msr_hi);
	msr_lo &= 0x0000007F;
	msr_hi &= 0x0000007F;

	if (longrun_high_freq <= longrun_low_freq) {
		/* Assume degenerate Longrun table */
		policy->min = policy->max = longrun_high_freq;
	} else {
		policy->min = longrun_low_freq + msr_lo *
			((longrun_high_freq - longrun_low_freq) / 100);
		policy->max = longrun_low_freq + msr_hi *
			((longrun_high_freq - longrun_low_freq) / 100);
	}
	policy->cpu = 0;
}


/**
 * longrun_set_policy - sets a new CPUFreq policy
 * @policy: new policy
 *
 * Sets a new CPUFreq policy on LongRun-capable processors. This function
 * has to be called with cpufreq_driver locked.
 */
static int longrun_set_policy(struct cpufreq_policy *policy)
{
	u32 msr_lo, msr_hi;
	u32 pctg_lo, pctg_hi;

	if (!policy)
		return -EINVAL;

	if (longrun_high_freq <= longrun_low_freq) {
		/* Assume degenerate Longrun table */
		pctg_lo = pctg_hi = 100;
	} else {
		pctg_lo = (policy->min - longrun_low_freq) /
			((longrun_high_freq - longrun_low_freq) / 100);
		pctg_hi = (policy->max - longrun_low_freq) /
			((longrun_high_freq - longrun_low_freq) / 100);
	}

	if (pctg_hi > 100)
		pctg_hi = 100;
	if (pctg_lo > pctg_hi)
		pctg_lo = pctg_hi;

	/* performance or economy mode */
	rdmsr(MSR_TMTA_LONGRUN_FLAGS, msr_lo, msr_hi);
	msr_lo &= 0xFFFFFFFE;
	switch (policy->policy) {
	case CPUFREQ_POLICY_PERFORMANCE:
		msr_lo |= 0x00000001;
		break;
	case CPUFREQ_POLICY_POWERSAVE:
		break;
	}
	wrmsr(MSR_TMTA_LONGRUN_FLAGS, msr_lo, msr_hi);

	/* lower and upper boundary */
	rdmsr(MSR_TMTA_LONGRUN_CTRL, msr_lo, msr_hi);
	msr_lo &= 0xFFFFFF80;
	msr_hi &= 0xFFFFFF80;
	msr_lo |= pctg_lo;
	msr_hi |= pctg_hi;
	wrmsr(MSR_TMTA_LONGRUN_CTRL, msr_lo, msr_hi);

	return 0;
}


/**
 * longrun_verify_poliy - verifies a new CPUFreq policy
 * @policy: the policy to verify
 *
 * Validates a new CPUFreq policy. This function has to be called with
 * cpufreq_driver locked.
 */
static int longrun_verify_policy(struct cpufreq_policy *policy)
{
	if (!policy)
		return -EINVAL;

	policy->cpu = 0;
	cpufreq_verify_within_limits(policy,
		policy->cpuinfo.min_freq,
		policy->cpuinfo.max_freq);

	if ((policy->policy != CPUFREQ_POLICY_POWERSAVE) &&
	    (policy->policy != CPUFREQ_POLICY_PERFORMANCE))
		return -EINVAL;

	return 0;
}

static unsigned int longrun_get(unsigned int cpu)
{
	u32 eax, ebx, ecx, edx;

	if (cpu)
		return 0;

	cpuid(0x80860007, &eax, &ebx, &ecx, &edx);
	dprintk("cpuid eax is %u\n", eax);

	return eax * 1000;
}

/**
 * longrun_determine_freqs - determines the lowest and highest possible core frequency
 * @low_freq: an int to put the lowest frequency into
 * @high_freq: an int to put the highest frequency into
 *
 * Determines the lowest and highest possible core frequencies on this CPU.
 * This is necessary to calculate the performance percentage according to
 * TMTA rules:
 * performance_pctg = (target_freq - low_freq)/(high_freq - low_freq)
 */
static unsigned int __cpuinit longrun_determine_freqs(unsigned int *low_freq,
						      unsigned int *high_freq)
{
	u32 msr_lo, msr_hi;
	u32 save_lo, save_hi;
	u32 eax, ebx, ecx, edx;
	u32 try_hi;
	struct cpuinfo_x86 *c = &cpu_data(0);

	if (!low_freq || !high_freq)
		return -EINVAL;

	if (cpu_has(c, X86_FEATURE_LRTI)) {
		/* if the LongRun Table Interface is present, the
		 * detection is a bit easier:
		 * For minimum frequency, read out the maximum
		 * level (msr_hi), write that into "currently
		 * selected level", and read out the frequency.
		 * For maximum frequency, read out level zero.
		 */
		/* minimum */
		rdmsr(MSR_TMTA_LRTI_READOUT, msr_lo, msr_hi);
		wrmsr(MSR_TMTA_LRTI_READOUT, msr_hi, msr_hi);
		rdmsr(MSR_TMTA_LRTI_VOLT_MHZ, msr_lo, msr_hi);
		*low_freq = msr_lo * 1000; /* to kHz */

		/* maximum */
		wrmsr(MSR_TMTA_LRTI_READOUT, 0, msr_hi);
		rdmsr(MSR_TMTA_LRTI_VOLT_MHZ, msr_lo, msr_hi);
		*high_freq = msr_lo * 1000; /* to kHz */

		dprintk("longrun table interface told %u - %u kHz\n",
				*low_freq, *high_freq);

		if (*low_freq > *high_freq)
			*low_freq = *high_freq;
		return 0;
	}

	/* set the upper border to the value determined during TSC init */
	*high_freq = (cpu_khz / 1000);
	*high_freq = *high_freq * 1000;
	dprintk("high frequency is %u kHz\n", *high_freq);

	/* get current borders */
	rdmsr(MSR_TMTA_LONGRUN_CTRL, msr_lo, msr_hi);
	save_lo = msr_lo & 0x0000007F;
	save_hi = msr_hi & 0x0000007F;

	/* if current perf_pctg is larger than 90%, we need to decrease the
	 * upper limit to make the calculation more accurate.
	 */
	cpuid(0x80860007, &eax, &ebx, &ecx, &edx);
	/* try decreasing in 10% steps, some processors react only
	 * on some barrier values */
	for (try_hi = 80; try_hi > 0 && ecx > 90; try_hi -= 10) {
		/* set to 0 to try_hi perf_pctg */
		msr_lo &= 0xFFFFFF80;
		msr_hi &= 0xFFFFFF80;
		msr_hi |= try_hi;
		wrmsr(MSR_TMTA_LONGRUN_CTRL, msr_lo, msr_hi);

		/* read out current core MHz and current perf_pctg */
		cpuid(0x80860007, &eax, &ebx, &ecx, &edx);

		/* restore values */
		wrmsr(MSR_TMTA_LONGRUN_CTRL, save_lo, save_hi);
	}
	dprintk("percentage is %u %%, freq is %u MHz\n", ecx, eax);

	/* performance_pctg = (current_freq - low_freq)/(high_freq - low_freq)
	 * eqals
	 * low_freq * (1 - perf_pctg) = (cur_freq - high_freq * perf_pctg)
	 *
	 * high_freq * perf_pctg is stored tempoarily into "ebx".
	 */
	ebx = (((cpu_khz / 1000) * ecx) / 100); /* to MHz */

	if ((ecx > 95) || (ecx == 0) || (eax < ebx))
		return -EIO;

	edx = ((eax - ebx) * 100) / (100 - ecx);
	*low_freq = edx * 1000; /* back to kHz */

	dprintk("low frequency is %u kHz\n", *low_freq);

	if (*low_freq > *high_freq)
		*low_freq = *high_freq;

	return 0;
}


static int __cpuinit longrun_cpu_init(struct cpufreq_policy *policy)
{
	int result = 0;

	/* capability check */
	if (policy->cpu != 0)
		return -ENODEV;

	/* detect low and high frequency */
	result = longrun_determine_freqs(&longrun_low_freq, &longrun_high_freq);
	if (result)
		return result;

	/* cpuinfo and default policy values */
	policy->cpuinfo.min_freq = longrun_low_freq;
	policy->cpuinfo.max_freq = longrun_high_freq;
	policy->cpuinfo.transition_latency = CPUFREQ_ETERNAL;
	longrun_get_policy(policy);

	return 0;
}


static struct cpufreq_driver longrun_driver = {
	.flags		= CPUFREQ_CONST_LOOPS,
	.verify		= longrun_verify_policy,
	.setpolicy	= longrun_set_policy,
	.get		= longrun_get,
	.init		= longrun_cpu_init,
	.name		= "longrun",
	.owner		= THIS_MODULE,
};


/**
 * longrun_init - initializes the Transmeta Crusoe LongRun CPUFreq driver
 *
 * Initializes the LongRun support.
 */
static int __init longrun_init(void)
{
	struct cpuinfo_x86 *c = &cpu_data(0);

	if (c->x86_vendor != X86_VENDOR_TRANSMETA ||
	    !cpu_has(c, X86_FEATURE_LONGRUN))
		return -ENODEV;

	return cpufreq_register_driver(&longrun_driver);
}


/**
 * longrun_exit - unregisters LongRun support
 */
static void __exit longrun_exit(void)
{
	cpufreq_unregister_driver(&longrun_driver);
}


MODULE_AUTHOR("Dominik Brodowski <linux@brodo.de>");
MODULE_DESCRIPTION("LongRun driver for Transmeta Crusoe and "
		"Efficeon processors.");
MODULE_LICENSE("GPL");

module_init(longrun_init);
module_exit(longrun_exit);