1// SPDX-License-Identifier: GPL-2.0
2#include <linux/bitops.h>
3#include <linux/delay.h>
4#include <linux/isa-dma.h>
5#include <linux/pci.h>
6#include <asm/dma.h>
7#include <linux/io.h>
8#include <asm/processor-cyrix.h>
9#include <asm/processor-flags.h>
10#include <linux/timer.h>
11#include <asm/pci-direct.h>
12#include <asm/tsc.h>
13#include <asm/cpufeature.h>
14#include <linux/sched.h>
15#include <linux/sched/clock.h>
16
17#include "cpu.h"
18
19/*
20 * Read NSC/Cyrix DEVID registers (DIR) to get more detailed info. about the CPU
21 */
22static void __do_cyrix_devid(unsigned char *dir0, unsigned char *dir1)
23{
24 unsigned char ccr2, ccr3;
25
26 /* we test for DEVID by checking whether CCR3 is writable */
27 ccr3 = getCx86(CX86_CCR3);
28 setCx86(CX86_CCR3, data: ccr3 ^ 0x80);
29 getCx86(reg: 0xc0); /* dummy to change bus */
30
31 if (getCx86(CX86_CCR3) == ccr3) { /* no DEVID regs. */
32 ccr2 = getCx86(CX86_CCR2);
33 setCx86(CX86_CCR2, data: ccr2 ^ 0x04);
34 getCx86(reg: 0xc0); /* dummy */
35
36 if (getCx86(CX86_CCR2) == ccr2) /* old Cx486SLC/DLC */
37 *dir0 = 0xfd;
38 else { /* Cx486S A step */
39 setCx86(CX86_CCR2, data: ccr2);
40 *dir0 = 0xfe;
41 }
42 } else {
43 setCx86(CX86_CCR3, data: ccr3); /* restore CCR3 */
44
45 /* read DIR0 and DIR1 CPU registers */
46 *dir0 = getCx86(CX86_DIR0);
47 *dir1 = getCx86(CX86_DIR1);
48 }
49}
50
51static void do_cyrix_devid(unsigned char *dir0, unsigned char *dir1)
52{
53 unsigned long flags;
54
55 local_irq_save(flags);
56 __do_cyrix_devid(dir0, dir1);
57 local_irq_restore(flags);
58}
59/*
60 * Cx86_dir0_msb is a HACK needed by check_cx686_cpuid/slop in bugs.h in
61 * order to identify the Cyrix CPU model after we're out of setup.c
62 *
63 * Actually since bugs.h doesn't even reference this perhaps someone should
64 * fix the documentation ???
65 */
66static unsigned char Cx86_dir0_msb = 0;
67
68static const char Cx86_model[][9] = {
69 "Cx486", "Cx486", "5x86 ", "6x86", "MediaGX ", "6x86MX ",
70 "M II ", "Unknown"
71};
72static const char Cx486_name[][5] = {
73 "SLC", "DLC", "SLC2", "DLC2", "SRx", "DRx",
74 "SRx2", "DRx2"
75};
76static const char Cx486S_name[][4] = {
77 "S", "S2", "Se", "S2e"
78};
79static const char Cx486D_name[][4] = {
80 "DX", "DX2", "?", "?", "?", "DX4"
81};
82static char Cx86_cb[] = "?.5x Core/Bus Clock";
83static const char cyrix_model_mult1[] = "12??43";
84static const char cyrix_model_mult2[] = "12233445";
85
86/*
87 * Reset the slow-loop (SLOP) bit on the 686(L) which is set by some old
88 * BIOSes for compatibility with DOS games. This makes the udelay loop
89 * work correctly, and improves performance.
90 *
91 * FIXME: our newer udelay uses the tsc. We don't need to frob with SLOP
92 */
93
94static void check_cx686_slop(struct cpuinfo_x86 *c)
95{
96 unsigned long flags;
97
98 if (Cx86_dir0_msb == 3) {
99 unsigned char ccr3, ccr5;
100
101 local_irq_save(flags);
102 ccr3 = getCx86(CX86_CCR3);
103 setCx86(CX86_CCR3, data: (ccr3 & 0x0f) | 0x10); /* enable MAPEN */
104 ccr5 = getCx86(CX86_CCR5);
105 if (ccr5 & 2)
106 setCx86(CX86_CCR5, data: ccr5 & 0xfd); /* reset SLOP */
107 setCx86(CX86_CCR3, data: ccr3); /* disable MAPEN */
108 local_irq_restore(flags);
109
110 if (ccr5 & 2) { /* possible wrong calibration done */
111 pr_info("Recalibrating delay loop with SLOP bit reset\n");
112 calibrate_delay();
113 c->loops_per_jiffy = loops_per_jiffy;
114 }
115 }
116}
117
118
119static void set_cx86_reorder(void)
120{
121 u8 ccr3;
122
123 pr_info("Enable Memory access reorder on Cyrix/NSC processor.\n");
124 ccr3 = getCx86(CX86_CCR3);
125 setCx86(CX86_CCR3, data: (ccr3 & 0x0f) | 0x10); /* enable MAPEN */
126
127 /* Load/Store Serialize to mem access disable (=reorder it) */
128 setCx86(CX86_PCR0, data: getCx86(CX86_PCR0) & ~0x80);
129 /* set load/store serialize from 1GB to 4GB */
130 ccr3 |= 0xe0;
131 setCx86(CX86_CCR3, data: ccr3);
132}
133
134static void set_cx86_memwb(void)
135{
136 pr_info("Enable Memory-Write-back mode on Cyrix/NSC processor.\n");
137
138 /* CCR2 bit 2: unlock NW bit */
139 setCx86(CX86_CCR2, data: getCx86(CX86_CCR2) & ~0x04);
140 /* set 'Not Write-through' */
141 write_cr0(x: read_cr0() | X86_CR0_NW);
142 /* CCR2 bit 2: lock NW bit and set WT1 */
143 setCx86(CX86_CCR2, data: getCx86(CX86_CCR2) | 0x14);
144}
145
146/*
147 * Configure later MediaGX and/or Geode processor.
148 */
149
150static void geode_configure(void)
151{
152 unsigned long flags;
153 u8 ccr3;
154 local_irq_save(flags);
155
156 /* Suspend on halt power saving */
157 setCx86(CX86_CCR2, data: getCx86(CX86_CCR2) | 0x08);
158
159 ccr3 = getCx86(CX86_CCR3);
160 setCx86(CX86_CCR3, data: (ccr3 & 0x0f) | 0x10); /* enable MAPEN */
161
162
163 /* FPU fast, DTE cache, Mem bypass */
164 setCx86(CX86_CCR4, data: getCx86(CX86_CCR4) | 0x38);
165 setCx86(CX86_CCR3, data: ccr3); /* disable MAPEN */
166
167 set_cx86_memwb();
168 set_cx86_reorder();
169
170 local_irq_restore(flags);
171}
172
173static void early_init_cyrix(struct cpuinfo_x86 *c)
174{
175 unsigned char dir0, dir0_msn, dir1 = 0;
176
177 __do_cyrix_devid(dir0: &dir0, dir1: &dir1);
178 dir0_msn = dir0 >> 4; /* identifies CPU "family" */
179
180 switch (dir0_msn) {
181 case 3: /* 6x86/6x86L */
182 /* Emulate MTRRs using Cyrix's ARRs. */
183 set_cpu_cap(c, X86_FEATURE_CYRIX_ARR);
184 break;
185 case 5: /* 6x86MX/M II */
186 /* Emulate MTRRs using Cyrix's ARRs. */
187 set_cpu_cap(c, X86_FEATURE_CYRIX_ARR);
188 break;
189 }
190}
191
192static void init_cyrix(struct cpuinfo_x86 *c)
193{
194 unsigned char dir0, dir0_msn, dir0_lsn, dir1 = 0;
195 char *buf = c->x86_model_id;
196 const char *p = NULL;
197
198 /*
199 * Bit 31 in normal CPUID used for nonstandard 3DNow ID;
200 * 3DNow is IDd by bit 31 in extended CPUID (1*32+31) anyway
201 */
202 clear_cpu_cap(c, bit: 0*32+31);
203
204 /* Cyrix used bit 24 in extended (AMD) CPUID for Cyrix MMX extensions */
205 if (test_cpu_cap(c, 1*32+24)) {
206 clear_cpu_cap(c, bit: 1*32+24);
207 set_cpu_cap(c, X86_FEATURE_CXMMX);
208 }
209
210 do_cyrix_devid(dir0: &dir0, dir1: &dir1);
211
212 check_cx686_slop(c);
213
214 Cx86_dir0_msb = dir0_msn = dir0 >> 4; /* identifies CPU "family" */
215 dir0_lsn = dir0 & 0xf; /* model or clock multiplier */
216
217 /* common case step number/rev -- exceptions handled below */
218 c->x86_model = (dir1 >> 4) + 1;
219 c->x86_stepping = dir1 & 0xf;
220
221 /* Now cook; the original recipe is by Channing Corn, from Cyrix.
222 * We do the same thing for each generation: we work out
223 * the model, multiplier and stepping. Black magic included,
224 * to make the silicon step/rev numbers match the printed ones.
225 */
226
227 switch (dir0_msn) {
228 unsigned char tmp;
229
230 case 0: /* Cx486SLC/DLC/SRx/DRx */
231 p = Cx486_name[dir0_lsn & 7];
232 break;
233
234 case 1: /* Cx486S/DX/DX2/DX4 */
235 p = (dir0_lsn & 8) ? Cx486D_name[dir0_lsn & 5]
236 : Cx486S_name[dir0_lsn & 3];
237 break;
238
239 case 2: /* 5x86 */
240 Cx86_cb[2] = cyrix_model_mult1[dir0_lsn & 5];
241 p = Cx86_cb+2;
242 break;
243
244 case 3: /* 6x86/6x86L */
245 Cx86_cb[1] = ' ';
246 Cx86_cb[2] = cyrix_model_mult1[dir0_lsn & 5];
247 if (dir1 > 0x21) { /* 686L */
248 Cx86_cb[0] = 'L';
249 p = Cx86_cb;
250 (c->x86_model)++;
251 } else /* 686 */
252 p = Cx86_cb+1;
253 /* Emulate MTRRs using Cyrix's ARRs. */
254 set_cpu_cap(c, X86_FEATURE_CYRIX_ARR);
255 /* 6x86's contain this bug */
256 set_cpu_bug(c, X86_BUG_COMA);
257 break;
258
259 case 4: /* MediaGX/GXm or Geode GXM/GXLV/GX1 */
260 case 11: /* GX1 with inverted Device ID */
261#ifdef CONFIG_PCI
262 {
263 u32 vendor, device;
264 /*
265 * It isn't really a PCI quirk directly, but the cure is the
266 * same. The MediaGX has deep magic SMM stuff that handles the
267 * SB emulation. It throws away the fifo on disable_dma() which
268 * is wrong and ruins the audio.
269 *
270 * Bug2: VSA1 has a wrap bug so that using maximum sized DMA
271 * causes bad things. According to NatSemi VSA2 has another
272 * bug to do with 'hlt'. I've not seen any boards using VSA2
273 * and X doesn't seem to support it either so who cares 8).
274 * VSA1 we work around however.
275 */
276
277 pr_info("Working around Cyrix MediaGX virtual DMA bugs.\n");
278 isa_dma_bridge_buggy = 2;
279
280 /* We do this before the PCI layer is running. However we
281 are safe here as we know the bridge must be a Cyrix
282 companion and must be present */
283 vendor = read_pci_config_16(bus: 0, slot: 0, func: 0x12, PCI_VENDOR_ID);
284 device = read_pci_config_16(bus: 0, slot: 0, func: 0x12, PCI_DEVICE_ID);
285
286 /*
287 * The 5510/5520 companion chips have a funky PIT.
288 */
289 if (vendor == PCI_VENDOR_ID_CYRIX &&
290 (device == PCI_DEVICE_ID_CYRIX_5510 ||
291 device == PCI_DEVICE_ID_CYRIX_5520))
292 mark_tsc_unstable(reason: "cyrix 5510/5520 detected");
293 }
294#endif
295 c->x86_cache_size = 16; /* Yep 16K integrated cache that's it */
296
297 /* GXm supports extended cpuid levels 'ala' AMD */
298 if (c->cpuid_level == 2) {
299 /* Enable cxMMX extensions (GX1 Datasheet 54) */
300 setCx86(CX86_CCR7, data: getCx86(CX86_CCR7) | 1);
301
302 /*
303 * GXm : 0x30 ... 0x5f GXm datasheet 51
304 * GXlv: 0x6x GXlv datasheet 54
305 * ? : 0x7x
306 * GX1 : 0x8x GX1 datasheet 56
307 */
308 if ((0x30 <= dir1 && dir1 <= 0x6f) ||
309 (0x80 <= dir1 && dir1 <= 0x8f))
310 geode_configure();
311 return;
312 } else { /* MediaGX */
313 Cx86_cb[2] = (dir0_lsn & 1) ? '3' : '4';
314 p = Cx86_cb+2;
315 c->x86_model = (dir1 & 0x20) ? 1 : 2;
316 }
317 break;
318
319 case 5: /* 6x86MX/M II */
320 if (dir1 > 7) {
321 dir0_msn++; /* M II */
322 /* Enable MMX extensions (App note 108) */
323 setCx86(CX86_CCR7, data: getCx86(CX86_CCR7)|1);
324 } else {
325 /* A 6x86MX - it has the bug. */
326 set_cpu_bug(c, X86_BUG_COMA);
327 }
328 tmp = (!(dir0_lsn & 7) || dir0_lsn & 1) ? 2 : 0;
329 Cx86_cb[tmp] = cyrix_model_mult2[dir0_lsn & 7];
330 p = Cx86_cb+tmp;
331 if (((dir1 & 0x0f) > 4) || ((dir1 & 0xf0) == 0x20))
332 (c->x86_model)++;
333 /* Emulate MTRRs using Cyrix's ARRs. */
334 set_cpu_cap(c, X86_FEATURE_CYRIX_ARR);
335 break;
336
337 case 0xf: /* Cyrix 486 without DEVID registers */
338 switch (dir0_lsn) {
339 case 0xd: /* either a 486SLC or DLC w/o DEVID */
340 dir0_msn = 0;
341 p = Cx486_name[!!boot_cpu_has(X86_FEATURE_FPU)];
342 break;
343
344 case 0xe: /* a 486S A step */
345 dir0_msn = 0;
346 p = Cx486S_name[0];
347 break;
348 }
349 break;
350
351 default: /* unknown (shouldn't happen, we know everyone ;-) */
352 dir0_msn = 7;
353 break;
354 }
355 strcpy(p: buf, q: Cx86_model[dir0_msn & 7]);
356 if (p)
357 strcat(p: buf, q: p);
358 return;
359}
360
361/*
362 * Handle National Semiconductor branded processors
363 */
364static void init_nsc(struct cpuinfo_x86 *c)
365{
366 /*
367 * There may be GX1 processors in the wild that are branded
368 * NSC and not Cyrix.
369 *
370 * This function only handles the GX processor, and kicks every
371 * thing else to the Cyrix init function above - that should
372 * cover any processors that might have been branded differently
373 * after NSC acquired Cyrix.
374 *
375 * If this breaks your GX1 horribly, please e-mail
376 * info-linux@ldcmail.amd.com to tell us.
377 */
378
379 /* Handle the GX (Formally known as the GX2) */
380
381 if (c->x86 == 5 && c->x86_model == 5)
382 cpu_detect_cache_sizes(c);
383 else
384 init_cyrix(c);
385}
386
387/*
388 * Cyrix CPUs without cpuid or with cpuid not yet enabled can be detected
389 * by the fact that they preserve the flags across the division of 5/2.
390 * PII and PPro exhibit this behavior too, but they have cpuid available.
391 */
392
393/*
394 * Perform the Cyrix 5/2 test. A Cyrix won't change
395 * the flags, while other 486 chips will.
396 */
397static inline int test_cyrix_52div(void)
398{
399 unsigned int test;
400
401 __asm__ __volatile__(
402 "sahf\n\t" /* clear flags (%eax = 0x0005) */
403 "div %b2\n\t" /* divide 5 by 2 */
404 "lahf" /* store flags into %ah */
405 : "=a" (test)
406 : "0" (5), "q" (2)
407 : "cc");
408
409 /* AH is 0x02 on Cyrix after the divide.. */
410 return (unsigned char) (test >> 8) == 0x02;
411}
412
413static void cyrix_identify(struct cpuinfo_x86 *c)
414{
415 /* Detect Cyrix with disabled CPUID */
416 if (c->x86 == 4 && test_cyrix_52div()) {
417 unsigned char dir0, dir1;
418
419 strcpy(p: c->x86_vendor_id, q: "CyrixInstead");
420 c->x86_vendor = X86_VENDOR_CYRIX;
421
422 /* Actually enable cpuid on the older cyrix */
423
424 /* Retrieve CPU revisions */
425
426 do_cyrix_devid(dir0: &dir0, dir1: &dir1);
427
428 dir0 >>= 4;
429
430 /* Check it is an affected model */
431
432 if (dir0 == 5 || dir0 == 3) {
433 unsigned char ccr3;
434 unsigned long flags;
435 pr_info("Enabling CPUID on Cyrix processor.\n");
436 local_irq_save(flags);
437 ccr3 = getCx86(CX86_CCR3);
438 /* enable MAPEN */
439 setCx86(CX86_CCR3, data: (ccr3 & 0x0f) | 0x10);
440 /* enable cpuid */
441 setCx86(CX86_CCR4, data: getCx86(CX86_CCR4) | 0x80);
442 /* disable MAPEN */
443 setCx86(CX86_CCR3, data: ccr3);
444 local_irq_restore(flags);
445 }
446 }
447}
448
449static const struct cpu_dev cyrix_cpu_dev = {
450 .c_vendor = "Cyrix",
451 .c_ident = { "CyrixInstead" },
452 .c_early_init = early_init_cyrix,
453 .c_init = init_cyrix,
454 .c_identify = cyrix_identify,
455 .c_x86_vendor = X86_VENDOR_CYRIX,
456};
457
458cpu_dev_register(cyrix_cpu_dev);
459
460static const struct cpu_dev nsc_cpu_dev = {
461 .c_vendor = "NSC",
462 .c_ident = { "Geode by NSC" },
463 .c_init = init_nsc,
464 .c_x86_vendor = X86_VENDOR_NSC,
465};
466
467cpu_dev_register(nsc_cpu_dev);
468

source code of linux/arch/x86/kernel/cpu/cyrix.c