1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3  *  Based on documentation provided by Dave Jones. Thanks!
4  *
5  *  BIG FAT DISCLAIMER: Work in progress code. Possibly *dangerous*
6  */
7 
8 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
9 
10 #include <linux/kernel.h>
11 #include <linux/module.h>
12 #include <linux/init.h>
13 #include <linux/cpufreq.h>
14 #include <linux/ioport.h>
15 #include <linux/slab.h>
16 #include <linux/timex.h>
17 #include <linux/io.h>
18 #include <linux/delay.h>
19 
20 #include <asm/cpu_device_id.h>
21 #include <asm/msr.h>
22 #include <asm/tsc.h>
23 
24 #if IS_ENABLED(CONFIG_ACPI_PROCESSOR)
25 #include <linux/acpi.h>
26 #include <acpi/processor.h>
27 #endif
28 
29 #define EPS_BRAND_C7M	0
30 #define EPS_BRAND_C7	1
31 #define EPS_BRAND_EDEN	2
32 #define EPS_BRAND_C3	3
33 #define EPS_BRAND_C7D	4
34 
35 struct eps_cpu_data {
36 	u32 fsb;
37 #if IS_ENABLED(CONFIG_ACPI_PROCESSOR)
38 	u32 bios_limit;
39 #endif
40 	struct cpufreq_frequency_table freq_table[];
41 };
42 
43 static struct eps_cpu_data *eps_cpu[NR_CPUS];
44 
45 /* Module parameters */
46 static int freq_failsafe_off;
47 static int voltage_failsafe_off;
48 static int set_max_voltage;
49 
50 #if IS_ENABLED(CONFIG_ACPI_PROCESSOR)
51 static int ignore_acpi_limit;
52 
53 static struct acpi_processor_performance *eps_acpi_cpu_perf;
54 
55 /* Minimum necessary to get acpi_processor_get_bios_limit() working */
56 static int eps_acpi_init(void)
57 {
58 	eps_acpi_cpu_perf = kzalloc(sizeof(*eps_acpi_cpu_perf),
59 				      GFP_KERNEL);
60 	if (!eps_acpi_cpu_perf)
61 		return -ENOMEM;
62 
63 	if (!zalloc_cpumask_var(&eps_acpi_cpu_perf->shared_cpu_map,
64 								GFP_KERNEL)) {
65 		kfree(eps_acpi_cpu_perf);
66 		eps_acpi_cpu_perf = NULL;
67 		return -ENOMEM;
68 	}
69 
70 	if (acpi_processor_register_performance(eps_acpi_cpu_perf, 0)) {
71 		free_cpumask_var(eps_acpi_cpu_perf->shared_cpu_map);
72 		kfree(eps_acpi_cpu_perf);
73 		eps_acpi_cpu_perf = NULL;
74 		return -EIO;
75 	}
76 	return 0;
77 }
78 
79 static int eps_acpi_exit(struct cpufreq_policy *policy)
80 {
81 	if (eps_acpi_cpu_perf) {
82 		acpi_processor_unregister_performance(0);
83 		free_cpumask_var(eps_acpi_cpu_perf->shared_cpu_map);
84 		kfree(eps_acpi_cpu_perf);
85 		eps_acpi_cpu_perf = NULL;
86 	}
87 	return 0;
88 }
89 #endif
90 
91 static unsigned int eps_get(unsigned int cpu)
92 {
93 	struct eps_cpu_data *centaur;
94 	u32 lo, hi;
95 
96 	if (cpu)
97 		return 0;
98 	centaur = eps_cpu[cpu];
99 	if (centaur == NULL)
100 		return 0;
101 
102 	/* Return current frequency */
103 	rdmsr(MSR_IA32_PERF_STATUS, lo, hi);
104 	return centaur->fsb * ((lo >> 8) & 0xff);
105 }
106 
107 static int eps_set_state(struct eps_cpu_data *centaur,
108 			 struct cpufreq_policy *policy,
109 			 u32 dest_state)
110 {
111 	u32 lo, hi;
112 	int i;
113 
114 	/* Wait while CPU is busy */
115 	rdmsr(MSR_IA32_PERF_STATUS, lo, hi);
116 	i = 0;
117 	while (lo & ((1 << 16) | (1 << 17))) {
118 		udelay(16);
119 		rdmsr(MSR_IA32_PERF_STATUS, lo, hi);
120 		i++;
121 		if (unlikely(i > 64)) {
122 			return -ENODEV;
123 		}
124 	}
125 	/* Set new multiplier and voltage */
126 	wrmsr(MSR_IA32_PERF_CTL, dest_state & 0xffff, 0);
127 	/* Wait until transition end */
128 	i = 0;
129 	do {
130 		udelay(16);
131 		rdmsr(MSR_IA32_PERF_STATUS, lo, hi);
132 		i++;
133 		if (unlikely(i > 64)) {
134 			return -ENODEV;
135 		}
136 	} while (lo & ((1 << 16) | (1 << 17)));
137 
138 #ifdef DEBUG
139 	{
140 	u8 current_multiplier, current_voltage;
141 
142 	/* Print voltage and multiplier */
143 	rdmsr(MSR_IA32_PERF_STATUS, lo, hi);
144 	current_voltage = lo & 0xff;
145 	pr_info("Current voltage = %dmV\n", current_voltage * 16 + 700);
146 	current_multiplier = (lo >> 8) & 0xff;
147 	pr_info("Current multiplier = %d\n", current_multiplier);
148 	}
149 #endif
150 	return 0;
151 }
152 
153 static int eps_target(struct cpufreq_policy *policy, unsigned int index)
154 {
155 	struct eps_cpu_data *centaur;
156 	unsigned int cpu = policy->cpu;
157 	unsigned int dest_state;
158 	int ret;
159 
160 	if (unlikely(eps_cpu[cpu] == NULL))
161 		return -ENODEV;
162 	centaur = eps_cpu[cpu];
163 
164 	/* Make frequency transition */
165 	dest_state = centaur->freq_table[index].driver_data & 0xffff;
166 	ret = eps_set_state(centaur, policy, dest_state);
167 	if (ret)
168 		pr_err("Timeout!\n");
169 	return ret;
170 }
171 
172 static int eps_cpu_init(struct cpufreq_policy *policy)
173 {
174 	unsigned int i;
175 	u32 lo, hi;
176 	u64 val;
177 	u8 current_multiplier, current_voltage;
178 	u8 max_multiplier, max_voltage;
179 	u8 min_multiplier, min_voltage;
180 	u8 brand = 0;
181 	u32 fsb;
182 	struct eps_cpu_data *centaur;
183 	struct cpuinfo_x86 *c = &cpu_data(0);
184 	struct cpufreq_frequency_table *f_table;
185 	int k, step, voltage;
186 	int states;
187 #if IS_ENABLED(CONFIG_ACPI_PROCESSOR)
188 	unsigned int limit;
189 #endif
190 
191 	if (policy->cpu != 0)
192 		return -ENODEV;
193 
194 	/* Check brand */
195 	pr_info("Detected VIA ");
196 
197 	switch (c->x86_model) {
198 	case 10:
199 		rdmsr(0x1153, lo, hi);
200 		brand = (((lo >> 2) ^ lo) >> 18) & 3;
201 		pr_cont("Model A ");
202 		break;
203 	case 13:
204 		rdmsr(0x1154, lo, hi);
205 		brand = (((lo >> 4) ^ (lo >> 2))) & 0x000000ff;
206 		pr_cont("Model D ");
207 		break;
208 	}
209 
210 	switch (brand) {
211 	case EPS_BRAND_C7M:
212 		pr_cont("C7-M\n");
213 		break;
214 	case EPS_BRAND_C7:
215 		pr_cont("C7\n");
216 		break;
217 	case EPS_BRAND_EDEN:
218 		pr_cont("Eden\n");
219 		break;
220 	case EPS_BRAND_C7D:
221 		pr_cont("C7-D\n");
222 		break;
223 	case EPS_BRAND_C3:
224 		pr_cont("C3\n");
225 		return -ENODEV;
226 	}
227 	/* Enable Enhanced PowerSaver */
228 	rdmsrl(MSR_IA32_MISC_ENABLE, val);
229 	if (!(val & MSR_IA32_MISC_ENABLE_ENHANCED_SPEEDSTEP)) {
230 		val |= MSR_IA32_MISC_ENABLE_ENHANCED_SPEEDSTEP;
231 		wrmsrl(MSR_IA32_MISC_ENABLE, val);
232 		/* Can be locked at 0 */
233 		rdmsrl(MSR_IA32_MISC_ENABLE, val);
234 		if (!(val & MSR_IA32_MISC_ENABLE_ENHANCED_SPEEDSTEP)) {
235 			pr_info("Can't enable Enhanced PowerSaver\n");
236 			return -ENODEV;
237 		}
238 	}
239 
240 	/* Print voltage and multiplier */
241 	rdmsr(MSR_IA32_PERF_STATUS, lo, hi);
242 	current_voltage = lo & 0xff;
243 	pr_info("Current voltage = %dmV\n", current_voltage * 16 + 700);
244 	current_multiplier = (lo >> 8) & 0xff;
245 	pr_info("Current multiplier = %d\n", current_multiplier);
246 
247 	/* Print limits */
248 	max_voltage = hi & 0xff;
249 	pr_info("Highest voltage = %dmV\n", max_voltage * 16 + 700);
250 	max_multiplier = (hi >> 8) & 0xff;
251 	pr_info("Highest multiplier = %d\n", max_multiplier);
252 	min_voltage = (hi >> 16) & 0xff;
253 	pr_info("Lowest voltage = %dmV\n", min_voltage * 16 + 700);
254 	min_multiplier = (hi >> 24) & 0xff;
255 	pr_info("Lowest multiplier = %d\n", min_multiplier);
256 
257 	/* Sanity checks */
258 	if (current_multiplier == 0 || max_multiplier == 0
259 	    || min_multiplier == 0)
260 		return -EINVAL;
261 	if (current_multiplier > max_multiplier
262 	    || max_multiplier <= min_multiplier)
263 		return -EINVAL;
264 	if (current_voltage > 0x1f || max_voltage > 0x1f)
265 		return -EINVAL;
266 	if (max_voltage < min_voltage
267 	    || current_voltage < min_voltage
268 	    || current_voltage > max_voltage)
269 		return -EINVAL;
270 
271 	/* Check for systems using underclocked CPU */
272 	if (!freq_failsafe_off && max_multiplier != current_multiplier) {
273 		pr_info("Your processor is running at different frequency then its maximum. Aborting.\n");
274 		pr_info("You can use freq_failsafe_off option to disable this check.\n");
275 		return -EINVAL;
276 	}
277 	if (!voltage_failsafe_off && max_voltage != current_voltage) {
278 		pr_info("Your processor is running at different voltage then its maximum. Aborting.\n");
279 		pr_info("You can use voltage_failsafe_off option to disable this check.\n");
280 		return -EINVAL;
281 	}
282 
283 	/* Calc FSB speed */
284 	fsb = cpu_khz / current_multiplier;
285 
286 #if IS_ENABLED(CONFIG_ACPI_PROCESSOR)
287 	/* Check for ACPI processor speed limit */
288 	if (!ignore_acpi_limit && !eps_acpi_init()) {
289 		if (!acpi_processor_get_bios_limit(policy->cpu, &limit)) {
290 			pr_info("ACPI limit %u.%uGHz\n",
291 				limit/1000000,
292 				(limit%1000000)/10000);
293 			eps_acpi_exit(policy);
294 			/* Check if max_multiplier is in BIOS limits */
295 			if (limit && max_multiplier * fsb > limit) {
296 				pr_info("Aborting\n");
297 				return -EINVAL;
298 			}
299 		}
300 	}
301 #endif
302 
303 	/* Allow user to set lower maximum voltage then that reported
304 	 * by processor */
305 	if (brand == EPS_BRAND_C7M && set_max_voltage) {
306 		u32 v;
307 
308 		/* Change mV to something hardware can use */
309 		v = (set_max_voltage - 700) / 16;
310 		/* Check if voltage is within limits */
311 		if (v >= min_voltage && v <= max_voltage) {
312 			pr_info("Setting %dmV as maximum\n", v * 16 + 700);
313 			max_voltage = v;
314 		}
315 	}
316 
317 	/* Calc number of p-states supported */
318 	if (brand == EPS_BRAND_C7M)
319 		states = max_multiplier - min_multiplier + 1;
320 	else
321 		states = 2;
322 
323 	/* Allocate private data and frequency table for current cpu */
324 	centaur = kzalloc(struct_size(centaur, freq_table, states + 1),
325 			  GFP_KERNEL);
326 	if (!centaur)
327 		return -ENOMEM;
328 	eps_cpu[0] = centaur;
329 
330 	/* Copy basic values */
331 	centaur->fsb = fsb;
332 #if IS_ENABLED(CONFIG_ACPI_PROCESSOR)
333 	centaur->bios_limit = limit;
334 #endif
335 
336 	/* Fill frequency and MSR value table */
337 	f_table = &centaur->freq_table[0];
338 	if (brand != EPS_BRAND_C7M) {
339 		f_table[0].frequency = fsb * min_multiplier;
340 		f_table[0].driver_data = (min_multiplier << 8) | min_voltage;
341 		f_table[1].frequency = fsb * max_multiplier;
342 		f_table[1].driver_data = (max_multiplier << 8) | max_voltage;
343 		f_table[2].frequency = CPUFREQ_TABLE_END;
344 	} else {
345 		k = 0;
346 		step = ((max_voltage - min_voltage) * 256)
347 			/ (max_multiplier - min_multiplier);
348 		for (i = min_multiplier; i <= max_multiplier; i++) {
349 			voltage = (k * step) / 256 + min_voltage;
350 			f_table[k].frequency = fsb * i;
351 			f_table[k].driver_data = (i << 8) | voltage;
352 			k++;
353 		}
354 		f_table[k].frequency = CPUFREQ_TABLE_END;
355 	}
356 
357 	policy->cpuinfo.transition_latency = 140000; /* 844mV -> 700mV in ns */
358 	policy->freq_table = &centaur->freq_table[0];
359 
360 	return 0;
361 }
362 
363 static int eps_cpu_exit(struct cpufreq_policy *policy)
364 {
365 	unsigned int cpu = policy->cpu;
366 
367 	/* Bye */
368 	kfree(eps_cpu[cpu]);
369 	eps_cpu[cpu] = NULL;
370 	return 0;
371 }
372 
373 static struct cpufreq_driver eps_driver = {
374 	.verify		= cpufreq_generic_frequency_table_verify,
375 	.target_index	= eps_target,
376 	.init		= eps_cpu_init,
377 	.exit		= eps_cpu_exit,
378 	.get		= eps_get,
379 	.name		= "e_powersaver",
380 	.attr		= cpufreq_generic_attr,
381 };
382 
383 
384 /* This driver will work only on Centaur C7 processors with
385  * Enhanced SpeedStep/PowerSaver registers */
386 static const struct x86_cpu_id eps_cpu_id[] = {
387 	X86_MATCH_VENDOR_FAM_FEATURE(CENTAUR, 6, X86_FEATURE_EST, NULL),
388 	{}
389 };
390 MODULE_DEVICE_TABLE(x86cpu, eps_cpu_id);
391 
392 static int __init eps_init(void)
393 {
394 	if (!x86_match_cpu(eps_cpu_id) || boot_cpu_data.x86_model < 10)
395 		return -ENODEV;
396 	if (cpufreq_register_driver(&eps_driver))
397 		return -EINVAL;
398 	return 0;
399 }
400 
401 static void __exit eps_exit(void)
402 {
403 	cpufreq_unregister_driver(&eps_driver);
404 }
405 
406 /* Allow user to overclock his machine or to change frequency to higher after
407  * unloading module */
408 module_param(freq_failsafe_off, int, 0644);
409 MODULE_PARM_DESC(freq_failsafe_off, "Disable current vs max frequency check");
410 module_param(voltage_failsafe_off, int, 0644);
411 MODULE_PARM_DESC(voltage_failsafe_off, "Disable current vs max voltage check");
412 #if IS_ENABLED(CONFIG_ACPI_PROCESSOR)
413 module_param(ignore_acpi_limit, int, 0644);
414 MODULE_PARM_DESC(ignore_acpi_limit, "Don't check ACPI's processor speed limit");
415 #endif
416 module_param(set_max_voltage, int, 0644);
417 MODULE_PARM_DESC(set_max_voltage, "Set maximum CPU voltage (mV) C7-M only");
418 
419 MODULE_AUTHOR("Rafal Bilski <rafalbilski@interia.pl>");
420 MODULE_DESCRIPTION("Enhanced PowerSaver driver for VIA C7 CPU's.");
421 MODULE_LICENSE("GPL");
422 
423 module_init(eps_init);
424 module_exit(eps_exit);
425