1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * (C) 2002 - 2003  Dominik Brodowski <linux@brodo.de>
4 *
5 *  BIG FAT DISCLAIMER: Work in progress code. Possibly *dangerous*
6 */
7
8#include <linux/kernel.h>
9#include <linux/module.h>
10#include <linux/init.h>
11#include <linux/cpufreq.h>
12#include <linux/timex.h>
13
14#include <asm/msr.h>
15#include <asm/processor.h>
16#include <asm/cpu_device_id.h>
17
18static struct cpufreq_driver	longrun_driver;
19
20/**
21 * longrun_{low,high}_freq is needed for the conversion of cpufreq kHz
22 * values into per cent values. In TMTA microcode, the following is valid:
23 * performance_pctg = (current_freq - low_freq)/(high_freq - low_freq)
24 */
25static unsigned int longrun_low_freq, longrun_high_freq;
26
27
28/**
29 * longrun_get_policy - get the current LongRun policy
30 * @policy: struct cpufreq_policy where current policy is written into
31 *
32 * Reads the current LongRun policy by access to MSR_TMTA_LONGRUN_FLAGS
33 * and MSR_TMTA_LONGRUN_CTRL
34 */
35static void longrun_get_policy(struct cpufreq_policy *policy)
36{
37	u32 msr_lo, msr_hi;
38
39	rdmsr(MSR_TMTA_LONGRUN_FLAGS, msr_lo, msr_hi);
40	pr_debug("longrun flags are %x - %x\n", msr_lo, msr_hi);
41	if (msr_lo & 0x01)
42		policy->policy = CPUFREQ_POLICY_PERFORMANCE;
43	else
44		policy->policy = CPUFREQ_POLICY_POWERSAVE;
45
46	rdmsr(MSR_TMTA_LONGRUN_CTRL, msr_lo, msr_hi);
47	pr_debug("longrun ctrl is %x - %x\n", msr_lo, msr_hi);
48	msr_lo &= 0x0000007F;
49	msr_hi &= 0x0000007F;
50
51	if (longrun_high_freq <= longrun_low_freq) {
52		/* Assume degenerate Longrun table */
53		policy->min = policy->max = longrun_high_freq;
54	} else {
55		policy->min = longrun_low_freq + msr_lo *
56			((longrun_high_freq - longrun_low_freq) / 100);
57		policy->max = longrun_low_freq + msr_hi *
58			((longrun_high_freq - longrun_low_freq) / 100);
59	}
60	policy->cpu = 0;
61}
62
63
64/**
65 * longrun_set_policy - sets a new CPUFreq policy
66 * @policy: new policy
67 *
68 * Sets a new CPUFreq policy on LongRun-capable processors. This function
69 * has to be called with cpufreq_driver locked.
70 */
71static int longrun_set_policy(struct cpufreq_policy *policy)
72{
73	u32 msr_lo, msr_hi;
74	u32 pctg_lo, pctg_hi;
75
76	if (!policy)
77		return -EINVAL;
78
79	if (longrun_high_freq <= longrun_low_freq) {
80		/* Assume degenerate Longrun table */
81		pctg_lo = pctg_hi = 100;
82	} else {
83		pctg_lo = (policy->min - longrun_low_freq) /
84			((longrun_high_freq - longrun_low_freq) / 100);
85		pctg_hi = (policy->max - longrun_low_freq) /
86			((longrun_high_freq - longrun_low_freq) / 100);
87	}
88
89	if (pctg_hi > 100)
90		pctg_hi = 100;
91	if (pctg_lo > pctg_hi)
92		pctg_lo = pctg_hi;
93
94	/* performance or economy mode */
95	rdmsr(MSR_TMTA_LONGRUN_FLAGS, msr_lo, msr_hi);
96	msr_lo &= 0xFFFFFFFE;
97	switch (policy->policy) {
98	case CPUFREQ_POLICY_PERFORMANCE:
99		msr_lo |= 0x00000001;
100		break;
101	case CPUFREQ_POLICY_POWERSAVE:
102		break;
103	}
104	wrmsr(MSR_TMTA_LONGRUN_FLAGS, msr_lo, msr_hi);
105
106	/* lower and upper boundary */
107	rdmsr(MSR_TMTA_LONGRUN_CTRL, msr_lo, msr_hi);
108	msr_lo &= 0xFFFFFF80;
109	msr_hi &= 0xFFFFFF80;
110	msr_lo |= pctg_lo;
111	msr_hi |= pctg_hi;
112	wrmsr(MSR_TMTA_LONGRUN_CTRL, msr_lo, msr_hi);
113
114	return 0;
115}
116
117
118/**
119 * longrun_verify_poliy - verifies a new CPUFreq policy
120 * @policy: the policy to verify
121 *
122 * Validates a new CPUFreq policy. This function has to be called with
123 * cpufreq_driver locked.
124 */
125static int longrun_verify_policy(struct cpufreq_policy_data *policy)
126{
127	if (!policy)
128		return -EINVAL;
129
130	policy->cpu = 0;
131	cpufreq_verify_within_cpu_limits(policy);
132
133	return 0;
134}
135
136static unsigned int longrun_get(unsigned int cpu)
137{
138	u32 eax, ebx, ecx, edx;
139
140	if (cpu)
141		return 0;
142
143	cpuid(0x80860007, &eax, &ebx, &ecx, &edx);
144	pr_debug("cpuid eax is %u\n", eax);
145
146	return eax * 1000;
147}
148
149/**
150 * longrun_determine_freqs - determines the lowest and highest possible core frequency
151 * @low_freq: an int to put the lowest frequency into
152 * @high_freq: an int to put the highest frequency into
153 *
154 * Determines the lowest and highest possible core frequencies on this CPU.
155 * This is necessary to calculate the performance percentage according to
156 * TMTA rules:
157 * performance_pctg = (target_freq - low_freq)/(high_freq - low_freq)
158 */
159static int longrun_determine_freqs(unsigned int *low_freq,
160						      unsigned int *high_freq)
161{
162	u32 msr_lo, msr_hi;
163	u32 save_lo, save_hi;
164	u32 eax, ebx, ecx, edx;
165	u32 try_hi;
166	struct cpuinfo_x86 *c = &cpu_data(0);
167
168	if (!low_freq || !high_freq)
169		return -EINVAL;
170
171	if (cpu_has(c, X86_FEATURE_LRTI)) {
172		/* if the LongRun Table Interface is present, the
173		 * detection is a bit easier:
174		 * For minimum frequency, read out the maximum
175		 * level (msr_hi), write that into "currently
176		 * selected level", and read out the frequency.
177		 * For maximum frequency, read out level zero.
178		 */
179		/* minimum */
180		rdmsr(MSR_TMTA_LRTI_READOUT, msr_lo, msr_hi);
181		wrmsr(MSR_TMTA_LRTI_READOUT, msr_hi, msr_hi);
182		rdmsr(MSR_TMTA_LRTI_VOLT_MHZ, msr_lo, msr_hi);
183		*low_freq = msr_lo * 1000; /* to kHz */
184
185		/* maximum */
186		wrmsr(MSR_TMTA_LRTI_READOUT, 0, msr_hi);
187		rdmsr(MSR_TMTA_LRTI_VOLT_MHZ, msr_lo, msr_hi);
188		*high_freq = msr_lo * 1000; /* to kHz */
189
190		pr_debug("longrun table interface told %u - %u kHz\n",
191				*low_freq, *high_freq);
192
193		if (*low_freq > *high_freq)
194			*low_freq = *high_freq;
195		return 0;
196	}
197
198	/* set the upper border to the value determined during TSC init */
199	*high_freq = (cpu_khz / 1000);
200	*high_freq = *high_freq * 1000;
201	pr_debug("high frequency is %u kHz\n", *high_freq);
202
203	/* get current borders */
204	rdmsr(MSR_TMTA_LONGRUN_CTRL, msr_lo, msr_hi);
205	save_lo = msr_lo & 0x0000007F;
206	save_hi = msr_hi & 0x0000007F;
207
208	/* if current perf_pctg is larger than 90%, we need to decrease the
209	 * upper limit to make the calculation more accurate.
210	 */
211	cpuid(0x80860007, &eax, &ebx, &ecx, &edx);
212	/* try decreasing in 10% steps, some processors react only
213	 * on some barrier values */
214	for (try_hi = 80; try_hi > 0 && ecx > 90; try_hi -= 10) {
215		/* set to 0 to try_hi perf_pctg */
216		msr_lo &= 0xFFFFFF80;
217		msr_hi &= 0xFFFFFF80;
218		msr_hi |= try_hi;
219		wrmsr(MSR_TMTA_LONGRUN_CTRL, msr_lo, msr_hi);
220
221		/* read out current core MHz and current perf_pctg */
222		cpuid(0x80860007, &eax, &ebx, &ecx, &edx);
223
224		/* restore values */
225		wrmsr(MSR_TMTA_LONGRUN_CTRL, save_lo, save_hi);
226	}
227	pr_debug("percentage is %u %%, freq is %u MHz\n", ecx, eax);
228
229	/* performance_pctg = (current_freq - low_freq)/(high_freq - low_freq)
230	 * eqals
231	 * low_freq * (1 - perf_pctg) = (cur_freq - high_freq * perf_pctg)
232	 *
233	 * high_freq * perf_pctg is stored tempoarily into "ebx".
234	 */
235	ebx = (((cpu_khz / 1000) * ecx) / 100); /* to MHz */
236
237	if ((ecx > 95) || (ecx == 0) || (eax < ebx))
238		return -EIO;
239
240	edx = ((eax - ebx) * 100) / (100 - ecx);
241	*low_freq = edx * 1000; /* back to kHz */
242
243	pr_debug("low frequency is %u kHz\n", *low_freq);
244
245	if (*low_freq > *high_freq)
246		*low_freq = *high_freq;
247
248	return 0;
249}
250
251
252static int longrun_cpu_init(struct cpufreq_policy *policy)
253{
254	int result = 0;
255
256	/* capability check */
257	if (policy->cpu != 0)
258		return -ENODEV;
259
260	/* detect low and high frequency */
261	result = longrun_determine_freqs(&longrun_low_freq, &longrun_high_freq);
262	if (result)
263		return result;
264
265	/* cpuinfo and default policy values */
266	policy->cpuinfo.min_freq = longrun_low_freq;
267	policy->cpuinfo.max_freq = longrun_high_freq;
268	longrun_get_policy(policy);
269
270	return 0;
271}
272
273
274static struct cpufreq_driver longrun_driver = {
275	.flags		= CPUFREQ_CONST_LOOPS,
276	.verify		= longrun_verify_policy,
277	.setpolicy	= longrun_set_policy,
278	.get		= longrun_get,
279	.init		= longrun_cpu_init,
280	.name		= "longrun",
281};
282
283static const struct x86_cpu_id longrun_ids[] = {
284	X86_MATCH_VENDOR_FEATURE(TRANSMETA, X86_FEATURE_LONGRUN, NULL),
285	{}
286};
287MODULE_DEVICE_TABLE(x86cpu, longrun_ids);
288
289/**
290 * longrun_init - initializes the Transmeta Crusoe LongRun CPUFreq driver
291 *
292 * Initializes the LongRun support.
293 */
294static int __init longrun_init(void)
295{
296	if (!x86_match_cpu(longrun_ids))
297		return -ENODEV;
298	return cpufreq_register_driver(&longrun_driver);
299}
300
301
302/**
303 * longrun_exit - unregisters LongRun support
304 */
305static void __exit longrun_exit(void)
306{
307	cpufreq_unregister_driver(&longrun_driver);
308}
309
310
311MODULE_AUTHOR("Dominik Brodowski <linux@brodo.de>");
312MODULE_DESCRIPTION("LongRun driver for Transmeta Crusoe and "
313		"Efficeon processors.");
314MODULE_LICENSE("GPL");
315
316module_init(longrun_init);
317module_exit(longrun_exit);
318