1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3  * Intel SpeedStep SMI driver.
4  *
5  * (C) 2003  Hiroshi Miura <miura@da-cha.org>
6  */
7 
8 
9 /*********************************************************************
10  *                        SPEEDSTEP - DEFINITIONS                    *
11  *********************************************************************/
12 
13 #define pr_fmt(fmt) "cpufreq: " fmt
14 
15 #include <linux/kernel.h>
16 #include <linux/module.h>
17 #include <linux/moduleparam.h>
18 #include <linux/init.h>
19 #include <linux/cpufreq.h>
20 #include <linux/delay.h>
21 #include <linux/io.h>
22 #include <asm/ist.h>
23 #include <asm/cpu_device_id.h>
24 
25 #include "speedstep-lib.h"
26 
27 /* speedstep system management interface port/command.
28  *
29  * These parameters are got from IST-SMI BIOS call.
30  * If user gives it, these are used.
31  *
32  */
33 static int smi_port;
34 static int smi_cmd;
35 static unsigned int smi_sig;
36 
37 /* info about the processor */
38 static enum speedstep_processor speedstep_processor;
39 
40 /*
41  * There are only two frequency states for each processor. Values
42  * are in kHz for the time being.
43  */
44 static struct cpufreq_frequency_table speedstep_freqs[] = {
45 	{0, SPEEDSTEP_HIGH,	0},
46 	{0, SPEEDSTEP_LOW,	0},
47 	{0, 0,			CPUFREQ_TABLE_END},
48 };
49 
50 #define GET_SPEEDSTEP_OWNER 0
51 #define GET_SPEEDSTEP_STATE 1
52 #define SET_SPEEDSTEP_STATE 2
53 #define GET_SPEEDSTEP_FREQS 4
54 
55 /* how often shall the SMI call be tried if it failed, e.g. because
56  * of DMA activity going on? */
57 #define SMI_TRIES 5
58 
59 /**
60  * speedstep_smi_ownership
61  */
62 static int speedstep_smi_ownership(void)
63 {
64 	u32 command, result, magic, dummy;
65 	u32 function = GET_SPEEDSTEP_OWNER;
66 	unsigned char magic_data[] = "Copyright (c) 1999 Intel Corporation";
67 
68 	command = (smi_sig & 0xffffff00) | (smi_cmd & 0xff);
69 	magic = virt_to_phys(magic_data);
70 
71 	pr_debug("trying to obtain ownership with command %x at port %x\n",
72 			command, smi_port);
73 
74 	__asm__ __volatile__(
75 		"push %%ebp\n"
76 		"out %%al, (%%dx)\n"
77 		"pop %%ebp\n"
78 		: "=D" (result),
79 		  "=a" (dummy), "=b" (dummy), "=c" (dummy), "=d" (dummy),
80 		  "=S" (dummy)
81 		: "a" (command), "b" (function), "c" (0), "d" (smi_port),
82 		  "D" (0), "S" (magic)
83 		: "memory"
84 	);
85 
86 	pr_debug("result is %x\n", result);
87 
88 	return result;
89 }
90 
91 /**
92  * speedstep_smi_get_freqs - get SpeedStep preferred & current freq.
93  * @low: the low frequency value is placed here
94  * @high: the high frequency value is placed here
95  *
96  * Only available on later SpeedStep-enabled systems, returns false results or
97  * even hangs [cf. bugme.osdl.org # 1422] on earlier systems. Empirical testing
98  * shows that the latter occurs if !(ist_info.event & 0xFFFF).
99  */
100 static int speedstep_smi_get_freqs(unsigned int *low, unsigned int *high)
101 {
102 	u32 command, result = 0, edi, high_mhz, low_mhz, dummy;
103 	u32 state = 0;
104 	u32 function = GET_SPEEDSTEP_FREQS;
105 
106 	if (!(ist_info.event & 0xFFFF)) {
107 		pr_debug("bug #1422 -- can't read freqs from BIOS\n");
108 		return -ENODEV;
109 	}
110 
111 	command = (smi_sig & 0xffffff00) | (smi_cmd & 0xff);
112 
113 	pr_debug("trying to determine frequencies with command %x at port %x\n",
114 			command, smi_port);
115 
116 	__asm__ __volatile__(
117 		"push %%ebp\n"
118 		"out %%al, (%%dx)\n"
119 		"pop %%ebp"
120 		: "=a" (result),
121 		  "=b" (high_mhz),
122 		  "=c" (low_mhz),
123 		  "=d" (state), "=D" (edi), "=S" (dummy)
124 		: "a" (command),
125 		  "b" (function),
126 		  "c" (state),
127 		  "d" (smi_port), "S" (0), "D" (0)
128 	);
129 
130 	pr_debug("result %x, low_freq %u, high_freq %u\n",
131 			result, low_mhz, high_mhz);
132 
133 	/* abort if results are obviously incorrect... */
134 	if ((high_mhz + low_mhz) < 600)
135 		return -EINVAL;
136 
137 	*high = high_mhz * 1000;
138 	*low  = low_mhz  * 1000;
139 
140 	return result;
141 }
142 
143 /**
144  * speedstep_set_state - set the SpeedStep state
145  * @state: new processor frequency state (SPEEDSTEP_LOW or SPEEDSTEP_HIGH)
146  *
147  */
148 static void speedstep_set_state(unsigned int state)
149 {
150 	unsigned int result = 0, command, new_state, dummy;
151 	unsigned long flags;
152 	unsigned int function = SET_SPEEDSTEP_STATE;
153 	unsigned int retry = 0;
154 
155 	if (state > 0x1)
156 		return;
157 
158 	/* Disable IRQs */
159 	preempt_disable();
160 	local_irq_save(flags);
161 
162 	command = (smi_sig & 0xffffff00) | (smi_cmd & 0xff);
163 
164 	pr_debug("trying to set frequency to state %u "
165 		"with command %x at port %x\n",
166 		state, command, smi_port);
167 
168 	do {
169 		if (retry) {
170 			/*
171 			 * We need to enable interrupts, otherwise the blockage
172 			 * won't resolve.
173 			 *
174 			 * We disable preemption so that other processes don't
175 			 * run. If other processes were running, they could
176 			 * submit more DMA requests, making the blockage worse.
177 			 */
178 			pr_debug("retry %u, previous result %u, waiting...\n",
179 					retry, result);
180 			local_irq_enable();
181 			mdelay(retry * 50);
182 			local_irq_disable();
183 		}
184 		retry++;
185 		__asm__ __volatile__(
186 			"push %%ebp\n"
187 			"out %%al, (%%dx)\n"
188 			"pop %%ebp"
189 			: "=b" (new_state), "=D" (result),
190 			  "=c" (dummy), "=a" (dummy),
191 			  "=d" (dummy), "=S" (dummy)
192 			: "a" (command), "b" (function), "c" (state),
193 			  "d" (smi_port), "S" (0), "D" (0)
194 			);
195 	} while ((new_state != state) && (retry <= SMI_TRIES));
196 
197 	/* enable IRQs */
198 	local_irq_restore(flags);
199 	preempt_enable();
200 
201 	if (new_state == state)
202 		pr_debug("change to %u MHz succeeded after %u tries "
203 			"with result %u\n",
204 			(speedstep_freqs[new_state].frequency / 1000),
205 			retry, result);
206 	else
207 		pr_err("change to state %u failed with new_state %u and result %u\n",
208 		       state, new_state, result);
209 
210 	return;
211 }
212 
213 
214 /**
215  * speedstep_target - set a new CPUFreq policy
216  * @policy: new policy
217  * @index: index of new freq
218  *
219  * Sets a new CPUFreq policy/freq.
220  */
221 static int speedstep_target(struct cpufreq_policy *policy, unsigned int index)
222 {
223 	speedstep_set_state(index);
224 
225 	return 0;
226 }
227 
228 
229 static int speedstep_cpu_init(struct cpufreq_policy *policy)
230 {
231 	int result;
232 	unsigned int *low, *high;
233 
234 	/* capability check */
235 	if (policy->cpu != 0)
236 		return -ENODEV;
237 
238 	result = speedstep_smi_ownership();
239 	if (result) {
240 		pr_debug("fails in acquiring ownership of a SMI interface.\n");
241 		return -EINVAL;
242 	}
243 
244 	/* detect low and high frequency */
245 	low = &speedstep_freqs[SPEEDSTEP_LOW].frequency;
246 	high = &speedstep_freqs[SPEEDSTEP_HIGH].frequency;
247 
248 	result = speedstep_smi_get_freqs(low, high);
249 	if (result) {
250 		/* fall back to speedstep_lib.c dection mechanism:
251 		 * try both states out */
252 		pr_debug("could not detect low and high frequencies "
253 				"by SMI call.\n");
254 		result = speedstep_get_freqs(speedstep_processor,
255 				low, high,
256 				NULL,
257 				&speedstep_set_state);
258 
259 		if (result) {
260 			pr_debug("could not detect two different speeds"
261 					" -- aborting.\n");
262 			return result;
263 		} else
264 			pr_debug("workaround worked.\n");
265 	}
266 
267 	policy->freq_table = speedstep_freqs;
268 
269 	return 0;
270 }
271 
272 static unsigned int speedstep_get(unsigned int cpu)
273 {
274 	if (cpu)
275 		return -ENODEV;
276 	return speedstep_get_frequency(speedstep_processor);
277 }
278 
279 
280 static int speedstep_resume(struct cpufreq_policy *policy)
281 {
282 	int result = speedstep_smi_ownership();
283 
284 	if (result)
285 		pr_debug("fails in re-acquiring ownership of a SMI interface.\n");
286 
287 	return result;
288 }
289 
290 static struct cpufreq_driver speedstep_driver = {
291 	.name		= "speedstep-smi",
292 	.flags		= CPUFREQ_NO_AUTO_DYNAMIC_SWITCHING,
293 	.verify		= cpufreq_generic_frequency_table_verify,
294 	.target_index	= speedstep_target,
295 	.init		= speedstep_cpu_init,
296 	.get		= speedstep_get,
297 	.resume		= speedstep_resume,
298 	.attr		= cpufreq_generic_attr,
299 };
300 
301 static const struct x86_cpu_id ss_smi_ids[] = {
302 	X86_MATCH_VENDOR_FAM_MODEL(INTEL,  6, 0x8, 0),
303 	X86_MATCH_VENDOR_FAM_MODEL(INTEL,  6, 0xb, 0),
304 	X86_MATCH_VENDOR_FAM_MODEL(INTEL, 15, 0x2, 0),
305 	{}
306 };
307 
308 /**
309  * speedstep_init - initializes the SpeedStep CPUFreq driver
310  *
311  *   Initializes the SpeedStep support. Returns -ENODEV on unsupported
312  * BIOS, -EINVAL on problems during initiatization, and zero on
313  * success.
314  */
315 static int __init speedstep_init(void)
316 {
317 	if (!x86_match_cpu(ss_smi_ids))
318 		return -ENODEV;
319 
320 	speedstep_processor = speedstep_detect_processor();
321 
322 	switch (speedstep_processor) {
323 	case SPEEDSTEP_CPU_PIII_T:
324 	case SPEEDSTEP_CPU_PIII_C:
325 	case SPEEDSTEP_CPU_PIII_C_EARLY:
326 		break;
327 	default:
328 		speedstep_processor = 0;
329 	}
330 
331 	if (!speedstep_processor) {
332 		pr_debug("No supported Intel CPU detected.\n");
333 		return -ENODEV;
334 	}
335 
336 	pr_debug("signature:0x%.8x, command:0x%.8x, "
337 		"event:0x%.8x, perf_level:0x%.8x.\n",
338 		ist_info.signature, ist_info.command,
339 		ist_info.event, ist_info.perf_level);
340 
341 	/* Error if no IST-SMI BIOS or no PARM
342 		 sig= 'ISGE' aka 'Intel Speedstep Gate E' */
343 	if ((ist_info.signature !=  0x47534943) && (
344 	    (smi_port == 0) || (smi_cmd == 0)))
345 		return -ENODEV;
346 
347 	if (smi_sig == 1)
348 		smi_sig = 0x47534943;
349 	else
350 		smi_sig = ist_info.signature;
351 
352 	/* setup smi_port from MODLULE_PARM or BIOS */
353 	if ((smi_port > 0xff) || (smi_port < 0))
354 		return -EINVAL;
355 	else if (smi_port == 0)
356 		smi_port = ist_info.command & 0xff;
357 
358 	if ((smi_cmd > 0xff) || (smi_cmd < 0))
359 		return -EINVAL;
360 	else if (smi_cmd == 0)
361 		smi_cmd = (ist_info.command >> 16) & 0xff;
362 
363 	return cpufreq_register_driver(&speedstep_driver);
364 }
365 
366 
367 /**
368  * speedstep_exit - unregisters SpeedStep support
369  *
370  *   Unregisters SpeedStep support.
371  */
372 static void __exit speedstep_exit(void)
373 {
374 	cpufreq_unregister_driver(&speedstep_driver);
375 }
376 
377 module_param_hw(smi_port, int, ioport, 0444);
378 module_param(smi_cmd,  int, 0444);
379 module_param(smi_sig, uint, 0444);
380 
381 MODULE_PARM_DESC(smi_port, "Override the BIOS-given IST port with this value "
382 		"-- Intel's default setting is 0xb2");
383 MODULE_PARM_DESC(smi_cmd, "Override the BIOS-given IST command with this value "
384 		"-- Intel's default setting is 0x82");
385 MODULE_PARM_DESC(smi_sig, "Set to 1 to fake the IST signature when using the "
386 		"SMI interface.");
387 
388 MODULE_AUTHOR("Hiroshi Miura");
389 MODULE_DESCRIPTION("Speedstep driver for IST applet SMI interface.");
390 MODULE_LICENSE("GPL");
391 
392 module_init(speedstep_init);
393 module_exit(speedstep_exit);
394