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 */
33static int smi_port;
34static int smi_cmd;
35static unsigned int smi_sig;
36
37/* info about the processor */
38static 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 */
44static 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 */
62static 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 */
100static 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 */
148static 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 */
221static int speedstep_target(struct cpufreq_policy *policy, unsigned int index)
222{
223	speedstep_set_state(index);
224
225	return 0;
226}
227
228
229static 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
272static unsigned int speedstep_get(unsigned int cpu)
273{
274	if (cpu)
275		return -ENODEV;
276	return speedstep_get_frequency(speedstep_processor);
277}
278
279
280static 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
290static 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
301static 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 */
315static 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 */
372static void __exit speedstep_exit(void)
373{
374	cpufreq_unregister_driver(&speedstep_driver);
375}
376
377module_param_hw(smi_port, int, ioport, 0444);
378module_param(smi_cmd,  int, 0444);
379module_param(smi_sig, uint, 0444);
380
381MODULE_PARM_DESC(smi_port, "Override the BIOS-given IST port with this value "
382		"-- Intel's default setting is 0xb2");
383MODULE_PARM_DESC(smi_cmd, "Override the BIOS-given IST command with this value "
384		"-- Intel's default setting is 0x82");
385MODULE_PARM_DESC(smi_sig, "Set to 1 to fake the IST signature when using the "
386		"SMI interface.");
387
388MODULE_AUTHOR("Hiroshi Miura");
389MODULE_DESCRIPTION("Speedstep driver for IST applet SMI interface.");
390MODULE_LICENSE("GPL");
391
392module_init(speedstep_init);
393module_exit(speedstep_exit);
394