1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * (C) 2004-2006 Sebastian Witt <se.witt@gmx.net>
4 *
5 * Based upon reverse engineered information
6 *
7 * BIG FAT DISCLAIMER: Work in progress code. Possibly *dangerous*
8 */
9
10#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
11
12#include <linux/kernel.h>
13#include <linux/module.h>
14#include <linux/moduleparam.h>
15#include <linux/init.h>
16#include <linux/cpufreq.h>
17#include <linux/pci.h>
18#include <linux/delay.h>
19
20#define NFORCE2_XTAL 25
21#define NFORCE2_BOOTFSB 0x48
22#define NFORCE2_PLLENABLE 0xa8
23#define NFORCE2_PLLREG 0xa4
24#define NFORCE2_PLLADR 0xa0
25#define NFORCE2_PLL(mul, div) (0x100000 | (mul << 8) | div)
26
27#define NFORCE2_MIN_FSB 50
28#define NFORCE2_SAFE_DISTANCE 50
29
30/* Delay in ms between FSB changes */
31/* #define NFORCE2_DELAY 10 */
32
33/*
34 * nforce2_chipset:
35 * FSB is changed using the chipset
36 */
37static struct pci_dev *nforce2_dev;
38
39/* fid:
40 * multiplier * 10
41 */
42static int fid;
43
44/* min_fsb, max_fsb:
45 * minimum and maximum FSB (= FSB at boot time)
46 */
47static int min_fsb;
48static int max_fsb;
49
50MODULE_AUTHOR("Sebastian Witt <se.witt@gmx.net>");
51MODULE_DESCRIPTION("nForce2 FSB changing cpufreq driver");
52MODULE_LICENSE("GPL");
53
54module_param(fid, int, 0444);
55module_param(min_fsb, int, 0444);
56
57MODULE_PARM_DESC(fid, "CPU multiplier to use (11.5 = 115)");
58MODULE_PARM_DESC(min_fsb,
59 "Minimum FSB to use, if not defined: current FSB - 50");
60
61/**
62 * nforce2_calc_fsb - calculate FSB
63 * @pll: PLL value
64 *
65 * Calculates FSB from PLL value
66 */
67static int nforce2_calc_fsb(int pll)
68{
69 unsigned char mul, div;
70
71 mul = (pll >> 8) & 0xff;
72 div = pll & 0xff;
73
74 if (div > 0)
75 return NFORCE2_XTAL * mul / div;
76
77 return 0;
78}
79
80/**
81 * nforce2_calc_pll - calculate PLL value
82 * @fsb: FSB
83 *
84 * Calculate PLL value for given FSB
85 */
86static int nforce2_calc_pll(unsigned int fsb)
87{
88 unsigned char xmul, xdiv;
89 unsigned char mul = 0, div = 0;
90 int tried = 0;
91
92 /* Try to calculate multiplier and divider up to 4 times */
93 while (((mul == 0) || (div == 0)) && (tried <= 3)) {
94 for (xdiv = 2; xdiv <= 0x80; xdiv++)
95 for (xmul = 1; xmul <= 0xfe; xmul++)
96 if (nforce2_calc_fsb(NFORCE2_PLL(xmul, xdiv)) ==
97 fsb + tried) {
98 mul = xmul;
99 div = xdiv;
100 }
101 tried++;
102 }
103
104 if ((mul == 0) || (div == 0))
105 return -1;
106
107 return NFORCE2_PLL(mul, div);
108}
109
110/**
111 * nforce2_write_pll - write PLL value to chipset
112 * @pll: PLL value
113 *
114 * Writes new FSB PLL value to chipset
115 */
116static void nforce2_write_pll(int pll)
117{
118 int temp;
119
120 /* Set the pll addr. to 0x00 */
121 pci_write_config_dword(dev: nforce2_dev, NFORCE2_PLLADR, val: 0);
122
123 /* Now write the value in all 64 registers */
124 for (temp = 0; temp <= 0x3f; temp++)
125 pci_write_config_dword(dev: nforce2_dev, NFORCE2_PLLREG, val: pll);
126}
127
128/**
129 * nforce2_fsb_read - Read FSB
130 *
131 * Read FSB from chipset
132 * If bootfsb != 0, return FSB at boot-time
133 */
134static unsigned int nforce2_fsb_read(int bootfsb)
135{
136 struct pci_dev *nforce2_sub5;
137 u32 fsb, temp = 0;
138
139 /* Get chipset boot FSB from subdevice 5 (FSB at boot-time) */
140 nforce2_sub5 = pci_get_subsys(PCI_VENDOR_ID_NVIDIA, device: 0x01EF,
141 PCI_ANY_ID, PCI_ANY_ID, NULL);
142 if (!nforce2_sub5)
143 return 0;
144
145 pci_read_config_dword(dev: nforce2_sub5, NFORCE2_BOOTFSB, val: &fsb);
146 fsb /= 1000000;
147
148 /* Check if PLL register is already set */
149 pci_read_config_byte(dev: nforce2_dev, NFORCE2_PLLENABLE, val: (u8 *)&temp);
150
151 if (bootfsb || !temp)
152 return fsb;
153
154 /* Use PLL register FSB value */
155 pci_read_config_dword(dev: nforce2_dev, NFORCE2_PLLREG, val: &temp);
156 fsb = nforce2_calc_fsb(pll: temp);
157
158 return fsb;
159}
160
161/**
162 * nforce2_set_fsb - set new FSB
163 * @fsb: New FSB
164 *
165 * Sets new FSB
166 */
167static int nforce2_set_fsb(unsigned int fsb)
168{
169 u32 temp = 0;
170 unsigned int tfsb;
171 int diff;
172 int pll = 0;
173
174 if ((fsb > max_fsb) || (fsb < NFORCE2_MIN_FSB)) {
175 pr_err("FSB %d is out of range!\n", fsb);
176 return -EINVAL;
177 }
178
179 tfsb = nforce2_fsb_read(bootfsb: 0);
180 if (!tfsb) {
181 pr_err("Error while reading the FSB\n");
182 return -EINVAL;
183 }
184
185 /* First write? Then set actual value */
186 pci_read_config_byte(dev: nforce2_dev, NFORCE2_PLLENABLE, val: (u8 *)&temp);
187 if (!temp) {
188 pll = nforce2_calc_pll(fsb: tfsb);
189
190 if (pll < 0)
191 return -EINVAL;
192
193 nforce2_write_pll(pll);
194 }
195
196 /* Enable write access */
197 temp = 0x01;
198 pci_write_config_byte(dev: nforce2_dev, NFORCE2_PLLENABLE, val: (u8)temp);
199
200 diff = tfsb - fsb;
201
202 if (!diff)
203 return 0;
204
205 while ((tfsb != fsb) && (tfsb <= max_fsb) && (tfsb >= min_fsb)) {
206 if (diff < 0)
207 tfsb++;
208 else
209 tfsb--;
210
211 /* Calculate the PLL reg. value */
212 pll = nforce2_calc_pll(fsb: tfsb);
213 if (pll == -1)
214 return -EINVAL;
215
216 nforce2_write_pll(pll);
217#ifdef NFORCE2_DELAY
218 mdelay(NFORCE2_DELAY);
219#endif
220 }
221
222 temp = 0x40;
223 pci_write_config_byte(dev: nforce2_dev, NFORCE2_PLLADR, val: (u8)temp);
224
225 return 0;
226}
227
228/**
229 * nforce2_get - get the CPU frequency
230 * @cpu: CPU number
231 *
232 * Returns the CPU frequency
233 */
234static unsigned int nforce2_get(unsigned int cpu)
235{
236 if (cpu)
237 return 0;
238 return nforce2_fsb_read(bootfsb: 0) * fid * 100;
239}
240
241/**
242 * nforce2_target - set a new CPUFreq policy
243 * @policy: new policy
244 * @target_freq: the target frequency
245 * @relation: how that frequency relates to achieved frequency
246 * (CPUFREQ_RELATION_L or CPUFREQ_RELATION_H)
247 *
248 * Sets a new CPUFreq policy.
249 */
250static int nforce2_target(struct cpufreq_policy *policy,
251 unsigned int target_freq, unsigned int relation)
252{
253/* unsigned long flags; */
254 struct cpufreq_freqs freqs;
255 unsigned int target_fsb;
256
257 if ((target_freq > policy->max) || (target_freq < policy->min))
258 return -EINVAL;
259
260 target_fsb = target_freq / (fid * 100);
261
262 freqs.old = nforce2_get(cpu: policy->cpu);
263 freqs.new = target_fsb * fid * 100;
264
265 if (freqs.old == freqs.new)
266 return 0;
267
268 pr_debug("Old CPU frequency %d kHz, new %d kHz\n",
269 freqs.old, freqs.new);
270
271 cpufreq_freq_transition_begin(policy, freqs: &freqs);
272
273 /* Disable IRQs */
274 /* local_irq_save(flags); */
275
276 if (nforce2_set_fsb(fsb: target_fsb) < 0)
277 pr_err("Changing FSB to %d failed\n", target_fsb);
278 else
279 pr_debug("Changed FSB successfully to %d\n",
280 target_fsb);
281
282 /* Enable IRQs */
283 /* local_irq_restore(flags); */
284
285 cpufreq_freq_transition_end(policy, freqs: &freqs, transition_failed: 0);
286
287 return 0;
288}
289
290/**
291 * nforce2_verify - verifies a new CPUFreq policy
292 * @policy: new policy
293 */
294static int nforce2_verify(struct cpufreq_policy_data *policy)
295{
296 unsigned int fsb_pol_max;
297
298 fsb_pol_max = policy->max / (fid * 100);
299
300 if (policy->min < (fsb_pol_max * fid * 100))
301 policy->max = (fsb_pol_max + 1) * fid * 100;
302
303 cpufreq_verify_within_cpu_limits(policy);
304 return 0;
305}
306
307static int nforce2_cpu_init(struct cpufreq_policy *policy)
308{
309 unsigned int fsb;
310 unsigned int rfid;
311
312 /* capability check */
313 if (policy->cpu != 0)
314 return -ENODEV;
315
316 /* Get current FSB */
317 fsb = nforce2_fsb_read(bootfsb: 0);
318
319 if (!fsb)
320 return -EIO;
321
322 /* FIX: Get FID from CPU */
323 if (!fid) {
324 if (!cpu_khz) {
325 pr_warn("cpu_khz not set, can't calculate multiplier!\n");
326 return -ENODEV;
327 }
328
329 fid = cpu_khz / (fsb * 100);
330 rfid = fid % 5;
331
332 if (rfid) {
333 if (rfid > 2)
334 fid += 5 - rfid;
335 else
336 fid -= rfid;
337 }
338 }
339
340 pr_info("FSB currently at %i MHz, FID %d.%d\n",
341 fsb, fid / 10, fid % 10);
342
343 /* Set maximum FSB to FSB at boot time */
344 max_fsb = nforce2_fsb_read(bootfsb: 1);
345
346 if (!max_fsb)
347 return -EIO;
348
349 if (!min_fsb)
350 min_fsb = max_fsb - NFORCE2_SAFE_DISTANCE;
351
352 if (min_fsb < NFORCE2_MIN_FSB)
353 min_fsb = NFORCE2_MIN_FSB;
354
355 /* cpuinfo and default policy values */
356 policy->min = policy->cpuinfo.min_freq = min_fsb * fid * 100;
357 policy->max = policy->cpuinfo.max_freq = max_fsb * fid * 100;
358
359 return 0;
360}
361
362static int nforce2_cpu_exit(struct cpufreq_policy *policy)
363{
364 return 0;
365}
366
367static struct cpufreq_driver nforce2_driver = {
368 .name = "nforce2",
369 .flags = CPUFREQ_NO_AUTO_DYNAMIC_SWITCHING,
370 .verify = nforce2_verify,
371 .target = nforce2_target,
372 .get = nforce2_get,
373 .init = nforce2_cpu_init,
374 .exit = nforce2_cpu_exit,
375};
376
377#ifdef MODULE
378static const struct pci_device_id nforce2_ids[] = {
379 { PCI_VENDOR_ID_NVIDIA, PCI_DEVICE_ID_NVIDIA_NFORCE2 },
380 {}
381};
382MODULE_DEVICE_TABLE(pci, nforce2_ids);
383#endif
384
385/**
386 * nforce2_detect_chipset - detect the Southbridge which contains FSB PLL logic
387 *
388 * Detects nForce2 A2 and C1 stepping
389 *
390 */
391static int nforce2_detect_chipset(void)
392{
393 nforce2_dev = pci_get_subsys(PCI_VENDOR_ID_NVIDIA,
394 PCI_DEVICE_ID_NVIDIA_NFORCE2,
395 PCI_ANY_ID, PCI_ANY_ID, NULL);
396
397 if (nforce2_dev == NULL)
398 return -ENODEV;
399
400 pr_info("Detected nForce2 chipset revision %X\n",
401 nforce2_dev->revision);
402 pr_info("FSB changing is maybe unstable and can lead to crashes and data loss\n");
403
404 return 0;
405}
406
407/**
408 * nforce2_init - initializes the nForce2 CPUFreq driver
409 *
410 * Initializes the nForce2 FSB support. Returns -ENODEV on unsupported
411 * devices, -EINVAL on problems during initialization, and zero on
412 * success.
413 */
414static int __init nforce2_init(void)
415{
416 /* TODO: do we need to detect the processor? */
417
418 /* detect chipset */
419 if (nforce2_detect_chipset()) {
420 pr_info("No nForce2 chipset\n");
421 return -ENODEV;
422 }
423
424 return cpufreq_register_driver(driver_data: &nforce2_driver);
425}
426
427/**
428 * nforce2_exit - unregisters cpufreq module
429 *
430 * Unregisters nForce2 FSB change support.
431 */
432static void __exit nforce2_exit(void)
433{
434 cpufreq_unregister_driver(driver_data: &nforce2_driver);
435}
436
437module_init(nforce2_init);
438module_exit(nforce2_exit);
439

source code of linux/drivers/cpufreq/cpufreq-nforce2.c