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  */
37 static struct pci_dev *nforce2_dev;
38 
39 /* fid:
40  * multiplier * 10
41  */
42 static int fid;
43 
44 /* min_fsb, max_fsb:
45  * minimum and maximum FSB (= FSB at boot time)
46  */
47 static int min_fsb;
48 static int max_fsb;
49 
50 MODULE_AUTHOR("Sebastian Witt <se.witt@gmx.net>");
51 MODULE_DESCRIPTION("nForce2 FSB changing cpufreq driver");
52 MODULE_LICENSE("GPL");
53 
54 module_param(fid, int, 0444);
55 module_param(min_fsb, int, 0444);
56 
57 MODULE_PARM_DESC(fid, "CPU multiplier to use (11.5 = 115)");
58 MODULE_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  */
67 static 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  */
86 static 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  */
116 static void nforce2_write_pll(int pll)
117 {
118 	int temp;
119 
120 	/* Set the pll addr. to 0x00 */
121 	pci_write_config_dword(nforce2_dev, NFORCE2_PLLADR, 0);
122 
123 	/* Now write the value in all 64 registers */
124 	for (temp = 0; temp <= 0x3f; temp++)
125 		pci_write_config_dword(nforce2_dev, NFORCE2_PLLREG, 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  */
134 static 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, 0x01EF,
141 				PCI_ANY_ID, PCI_ANY_ID, NULL);
142 	if (!nforce2_sub5)
143 		return 0;
144 
145 	pci_read_config_dword(nforce2_sub5, NFORCE2_BOOTFSB, &fsb);
146 	fsb /= 1000000;
147 
148 	/* Check if PLL register is already set */
149 	pci_read_config_byte(nforce2_dev, NFORCE2_PLLENABLE, (u8 *)&temp);
150 
151 	if (bootfsb || !temp)
152 		return fsb;
153 
154 	/* Use PLL register FSB value */
155 	pci_read_config_dword(nforce2_dev, NFORCE2_PLLREG, &temp);
156 	fsb = nforce2_calc_fsb(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  */
167 static 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(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(nforce2_dev, NFORCE2_PLLENABLE, (u8 *)&temp);
187 	if (!temp) {
188 		pll = nforce2_calc_pll(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(nforce2_dev, NFORCE2_PLLENABLE, (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(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(nforce2_dev, NFORCE2_PLLADR, (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  */
234 static unsigned int nforce2_get(unsigned int cpu)
235 {
236 	if (cpu)
237 		return 0;
238 	return nforce2_fsb_read(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  */
250 static 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(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);
272 
273 	/* Disable IRQs */
274 	/* local_irq_save(flags); */
275 
276 	if (nforce2_set_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, 0);
286 
287 	return 0;
288 }
289 
290 /**
291  * nforce2_verify - verifies a new CPUFreq policy
292  * @policy: new policy
293  */
294 static int nforce2_verify(struct cpufreq_policy *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 
307 static 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(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(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 
362 static int nforce2_cpu_exit(struct cpufreq_policy *policy)
363 {
364 	return 0;
365 }
366 
367 static 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
378 static const struct pci_device_id nforce2_ids[] = {
379 	{ PCI_VENDOR_ID_NVIDIA, PCI_DEVICE_ID_NVIDIA_NFORCE2 },
380 	{}
381 };
382 MODULE_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  */
391 static 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  */
414 static 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(&nforce2_driver);
425 }
426 
427 /**
428  * nforce2_exit - unregisters cpufreq module
429  *
430  *   Unregisters nForce2 FSB change support.
431  */
432 static void __exit nforce2_exit(void)
433 {
434 	cpufreq_unregister_driver(&nforce2_driver);
435 }
436 
437 module_init(nforce2_init);
438 module_exit(nforce2_exit);
439