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
35struct 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
43static struct eps_cpu_data *eps_cpu[NR_CPUS];
44
45/* Module parameters */
46static int freq_failsafe_off;
47static int voltage_failsafe_off;
48static int set_max_voltage;
49
50#if IS_ENABLED(CONFIG_ACPI_PROCESSOR)
51static int ignore_acpi_limit;
52
53static struct acpi_processor_performance *eps_acpi_cpu_perf;
54
55/* Minimum necessary to get acpi_processor_get_bios_limit() working */
56static 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
79static 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
91static 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
107static 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
153static 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
172static 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
363static 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
373static 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 */
386static const struct x86_cpu_id eps_cpu_id[] = {
387	X86_MATCH_VENDOR_FAM_FEATURE(CENTAUR, 6, X86_FEATURE_EST, NULL),
388	{}
389};
390MODULE_DEVICE_TABLE(x86cpu, eps_cpu_id);
391
392static 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
401static 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 */
408module_param(freq_failsafe_off, int, 0644);
409MODULE_PARM_DESC(freq_failsafe_off, "Disable current vs max frequency check");
410module_param(voltage_failsafe_off, int, 0644);
411MODULE_PARM_DESC(voltage_failsafe_off, "Disable current vs max voltage check");
412#if IS_ENABLED(CONFIG_ACPI_PROCESSOR)
413module_param(ignore_acpi_limit, int, 0644);
414MODULE_PARM_DESC(ignore_acpi_limit, "Don't check ACPI's processor speed limit");
415#endif
416module_param(set_max_voltage, int, 0644);
417MODULE_PARM_DESC(set_max_voltage, "Set maximum CPU voltage (mV) C7-M only");
418
419MODULE_AUTHOR("Rafal Bilski <rafalbilski@interia.pl>");
420MODULE_DESCRIPTION("Enhanced PowerSaver driver for VIA C7 CPU's.");
421MODULE_LICENSE("GPL");
422
423module_init(eps_init);
424module_exit(eps_exit);
425