xref: /openbmc/linux/arch/arc/kernel/setup.c (revision 1c2dd16a)
1 /*
2  * Copyright (C) 2004, 2007-2010, 2011-2012 Synopsys, Inc. (www.synopsys.com)
3  *
4  * This program is free software; you can redistribute it and/or modify
5  * it under the terms of the GNU General Public License version 2 as
6  * published by the Free Software Foundation.
7  */
8 
9 #include <linux/seq_file.h>
10 #include <linux/fs.h>
11 #include <linux/delay.h>
12 #include <linux/root_dev.h>
13 #include <linux/clk.h>
14 #include <linux/clk-provider.h>
15 #include <linux/clocksource.h>
16 #include <linux/console.h>
17 #include <linux/module.h>
18 #include <linux/cpu.h>
19 #include <linux/of_fdt.h>
20 #include <linux/of.h>
21 #include <linux/cache.h>
22 #include <asm/sections.h>
23 #include <asm/arcregs.h>
24 #include <asm/tlb.h>
25 #include <asm/setup.h>
26 #include <asm/page.h>
27 #include <asm/irq.h>
28 #include <asm/unwind.h>
29 #include <asm/mach_desc.h>
30 #include <asm/smp.h>
31 
32 #define FIX_PTR(x)  __asm__ __volatile__(";" : "+r"(x))
33 
34 unsigned int intr_to_DE_cnt;
35 
36 /* Part of U-boot ABI: see head.S */
37 int __initdata uboot_tag;
38 char __initdata *uboot_arg;
39 
40 const struct machine_desc *machine_desc;
41 
42 struct task_struct *_current_task[NR_CPUS];	/* For stack switching */
43 
44 struct cpuinfo_arc cpuinfo_arc700[NR_CPUS];
45 
46 static const struct id_to_str arc_cpu_rel[] = {
47 #ifdef CONFIG_ISA_ARCOMPACT
48 	{ 0x34, "R4.10"},
49 	{ 0x35, "R4.11"},
50 #else
51 	{ 0x51, "R2.0" },
52 	{ 0x52, "R2.1" },
53 	{ 0x53, "R3.0" },
54 #endif
55 	{ 0x00, NULL   }
56 };
57 
58 static const struct id_to_str arc_cpu_nm[] = {
59 #ifdef CONFIG_ISA_ARCOMPACT
60 	{ 0x20, "ARC 600"   },
61 	{ 0x30, "ARC 770"   },  /* 750 identified seperately */
62 #else
63 	{ 0x40, "ARC EM"  },
64 	{ 0x50, "ARC HS38"  },
65 #endif
66 	{ 0x00, "Unknown"   }
67 };
68 
69 static void read_decode_ccm_bcr(struct cpuinfo_arc *cpu)
70 {
71 	if (is_isa_arcompact()) {
72 		struct bcr_iccm_arcompact iccm;
73 		struct bcr_dccm_arcompact dccm;
74 
75 		READ_BCR(ARC_REG_ICCM_BUILD, iccm);
76 		if (iccm.ver) {
77 			cpu->iccm.sz = 4096 << iccm.sz;	/* 8K to 512K */
78 			cpu->iccm.base_addr = iccm.base << 16;
79 		}
80 
81 		READ_BCR(ARC_REG_DCCM_BUILD, dccm);
82 		if (dccm.ver) {
83 			unsigned long base;
84 			cpu->dccm.sz = 2048 << dccm.sz;	/* 2K to 256K */
85 
86 			base = read_aux_reg(ARC_REG_DCCM_BASE_BUILD);
87 			cpu->dccm.base_addr = base & ~0xF;
88 		}
89 	} else {
90 		struct bcr_iccm_arcv2 iccm;
91 		struct bcr_dccm_arcv2 dccm;
92 		unsigned long region;
93 
94 		READ_BCR(ARC_REG_ICCM_BUILD, iccm);
95 		if (iccm.ver) {
96 			cpu->iccm.sz = 256 << iccm.sz00;	/* 512B to 16M */
97 			if (iccm.sz00 == 0xF && iccm.sz01 > 0)
98 				cpu->iccm.sz <<= iccm.sz01;
99 
100 			region = read_aux_reg(ARC_REG_AUX_ICCM);
101 			cpu->iccm.base_addr = region & 0xF0000000;
102 		}
103 
104 		READ_BCR(ARC_REG_DCCM_BUILD, dccm);
105 		if (dccm.ver) {
106 			cpu->dccm.sz = 256 << dccm.sz0;
107 			if (dccm.sz0 == 0xF && dccm.sz1 > 0)
108 				cpu->dccm.sz <<= dccm.sz1;
109 
110 			region = read_aux_reg(ARC_REG_AUX_DCCM);
111 			cpu->dccm.base_addr = region & 0xF0000000;
112 		}
113 	}
114 }
115 
116 static void read_arc_build_cfg_regs(void)
117 {
118 	struct bcr_timer timer;
119 	struct bcr_generic bcr;
120 	struct cpuinfo_arc *cpu = &cpuinfo_arc700[smp_processor_id()];
121 	const struct id_to_str *tbl;
122 
123 	FIX_PTR(cpu);
124 
125 	READ_BCR(AUX_IDENTITY, cpu->core);
126 	READ_BCR(ARC_REG_ISA_CFG_BCR, cpu->isa);
127 
128 	for (tbl = &arc_cpu_rel[0]; tbl->id != 0; tbl++) {
129 		if (cpu->core.family == tbl->id) {
130 			cpu->details = tbl->str;
131 			break;
132 		}
133 	}
134 
135 	for (tbl = &arc_cpu_nm[0]; tbl->id != 0; tbl++) {
136 		if ((cpu->core.family & 0xF0) == tbl->id)
137 			break;
138 	}
139 	cpu->name = tbl->str;
140 
141 	READ_BCR(ARC_REG_TIMERS_BCR, timer);
142 	cpu->extn.timer0 = timer.t0;
143 	cpu->extn.timer1 = timer.t1;
144 	cpu->extn.rtc = timer.rtc;
145 
146 	cpu->vec_base = read_aux_reg(AUX_INTR_VEC_BASE);
147 
148 	READ_BCR(ARC_REG_MUL_BCR, cpu->extn_mpy);
149 
150 	cpu->extn.norm = read_aux_reg(ARC_REG_NORM_BCR) > 1 ? 1 : 0; /* 2,3 */
151 	cpu->extn.barrel = read_aux_reg(ARC_REG_BARREL_BCR) > 1 ? 1 : 0; /* 2,3 */
152 	cpu->extn.swap = read_aux_reg(ARC_REG_SWAP_BCR) ? 1 : 0;        /* 1,3 */
153 	cpu->extn.crc = read_aux_reg(ARC_REG_CRC_BCR) ? 1 : 0;
154 	cpu->extn.minmax = read_aux_reg(ARC_REG_MIXMAX_BCR) > 1 ? 1 : 0; /* 2 */
155 	cpu->extn.swape = (cpu->core.family >= 0x34) ? 1 :
156 				IS_ENABLED(CONFIG_ARC_HAS_SWAPE);
157 
158 	READ_BCR(ARC_REG_XY_MEM_BCR, cpu->extn_xymem);
159 
160 	/* Read CCM BCRs for boot reporting even if not enabled in Kconfig */
161 	read_decode_ccm_bcr(cpu);
162 
163 	read_decode_mmu_bcr();
164 	read_decode_cache_bcr();
165 
166 	if (is_isa_arcompact()) {
167 		struct bcr_fp_arcompact sp, dp;
168 		struct bcr_bpu_arcompact bpu;
169 
170 		READ_BCR(ARC_REG_FP_BCR, sp);
171 		READ_BCR(ARC_REG_DPFP_BCR, dp);
172 		cpu->extn.fpu_sp = sp.ver ? 1 : 0;
173 		cpu->extn.fpu_dp = dp.ver ? 1 : 0;
174 
175 		READ_BCR(ARC_REG_BPU_BCR, bpu);
176 		cpu->bpu.ver = bpu.ver;
177 		cpu->bpu.full = bpu.fam ? 1 : 0;
178 		if (bpu.ent) {
179 			cpu->bpu.num_cache = 256 << (bpu.ent - 1);
180 			cpu->bpu.num_pred = 256 << (bpu.ent - 1);
181 		}
182 	} else {
183 		struct bcr_fp_arcv2 spdp;
184 		struct bcr_bpu_arcv2 bpu;
185 
186 		READ_BCR(ARC_REG_FP_V2_BCR, spdp);
187 		cpu->extn.fpu_sp = spdp.sp ? 1 : 0;
188 		cpu->extn.fpu_dp = spdp.dp ? 1 : 0;
189 
190 		READ_BCR(ARC_REG_BPU_BCR, bpu);
191 		cpu->bpu.ver = bpu.ver;
192 		cpu->bpu.full = bpu.ft;
193 		cpu->bpu.num_cache = 256 << bpu.bce;
194 		cpu->bpu.num_pred = 2048 << bpu.pte;
195 	}
196 
197 	READ_BCR(ARC_REG_AP_BCR, bcr);
198 	cpu->extn.ap = bcr.ver ? 1 : 0;
199 
200 	READ_BCR(ARC_REG_SMART_BCR, bcr);
201 	cpu->extn.smart = bcr.ver ? 1 : 0;
202 
203 	READ_BCR(ARC_REG_RTT_BCR, bcr);
204 	cpu->extn.rtt = bcr.ver ? 1 : 0;
205 
206 	cpu->extn.debug = cpu->extn.ap | cpu->extn.smart | cpu->extn.rtt;
207 
208 	/* some hacks for lack of feature BCR info in old ARC700 cores */
209 	if (is_isa_arcompact()) {
210 		if (!cpu->isa.ver)	/* ISA BCR absent, use Kconfig info */
211 			cpu->isa.atomic = IS_ENABLED(CONFIG_ARC_HAS_LLSC);
212 		else
213 			cpu->isa.atomic = cpu->isa.atomic1;
214 
215 		cpu->isa.be = IS_ENABLED(CONFIG_CPU_BIG_ENDIAN);
216 
217 		 /* there's no direct way to distinguish 750 vs. 770 */
218 		if (unlikely(cpu->core.family < 0x34 || cpu->mmu.ver < 3))
219 			cpu->name = "ARC750";
220 	}
221 }
222 
223 static char *arc_cpu_mumbojumbo(int cpu_id, char *buf, int len)
224 {
225 	struct cpuinfo_arc *cpu = &cpuinfo_arc700[cpu_id];
226 	struct bcr_identity *core = &cpu->core;
227 	int i, n = 0;
228 
229 	FIX_PTR(cpu);
230 
231 	n += scnprintf(buf + n, len - n,
232 		       "\nIDENTITY\t: ARCVER [%#02x] ARCNUM [%#02x] CHIPID [%#4x]\n",
233 		       core->family, core->cpu_id, core->chip_id);
234 
235 	n += scnprintf(buf + n, len - n, "processor [%d]\t: %s %s (%s ISA) %s\n",
236 		       cpu_id, cpu->name, cpu->details,
237 		       is_isa_arcompact() ? "ARCompact" : "ARCv2",
238 		       IS_AVAIL1(cpu->isa.be, "[Big-Endian]"));
239 
240 	n += scnprintf(buf + n, len - n, "Timers\t\t: %s%s%s%s%s%s\nISA Extn\t: ",
241 		       IS_AVAIL1(cpu->extn.timer0, "Timer0 "),
242 		       IS_AVAIL1(cpu->extn.timer1, "Timer1 "),
243 		       IS_AVAIL2(cpu->extn.rtc, "RTC [UP 64-bit] ", CONFIG_ARC_TIMERS_64BIT),
244 		       IS_AVAIL2(cpu->extn.gfrc, "GFRC [SMP 64-bit] ", CONFIG_ARC_TIMERS_64BIT));
245 
246 	n += i = scnprintf(buf + n, len - n, "%s%s%s%s%s",
247 			   IS_AVAIL2(cpu->isa.atomic, "atomic ", CONFIG_ARC_HAS_LLSC),
248 			   IS_AVAIL2(cpu->isa.ldd, "ll64 ", CONFIG_ARC_HAS_LL64),
249 			   IS_AVAIL1(cpu->isa.unalign, "unalign (not used)"));
250 
251 	if (i)
252 		n += scnprintf(buf + n, len - n, "\n\t\t: ");
253 
254 	if (cpu->extn_mpy.ver) {
255 		if (cpu->extn_mpy.ver <= 0x2) {	/* ARCompact */
256 			n += scnprintf(buf + n, len - n, "mpy ");
257 		} else {
258 			int opt = 2;	/* stock MPY/MPYH */
259 
260 			if (cpu->extn_mpy.dsp)	/* OPT 7-9 */
261 				opt = cpu->extn_mpy.dsp + 6;
262 
263 			n += scnprintf(buf + n, len - n, "mpy[opt %d] ", opt);
264 		}
265 	}
266 
267 	n += scnprintf(buf + n, len - n, "%s%s%s%s%s%s%s%s\n",
268 		       IS_AVAIL1(cpu->isa.div_rem, "div_rem "),
269 		       IS_AVAIL1(cpu->extn.norm, "norm "),
270 		       IS_AVAIL1(cpu->extn.barrel, "barrel-shift "),
271 		       IS_AVAIL1(cpu->extn.swap, "swap "),
272 		       IS_AVAIL1(cpu->extn.minmax, "minmax "),
273 		       IS_AVAIL1(cpu->extn.crc, "crc "),
274 		       IS_AVAIL2(cpu->extn.swape, "swape", CONFIG_ARC_HAS_SWAPE));
275 
276 	if (cpu->bpu.ver)
277 		n += scnprintf(buf + n, len - n,
278 			      "BPU\t\t: %s%s match, cache:%d, Predict Table:%d\n",
279 			      IS_AVAIL1(cpu->bpu.full, "full"),
280 			      IS_AVAIL1(!cpu->bpu.full, "partial"),
281 			      cpu->bpu.num_cache, cpu->bpu.num_pred);
282 
283 	return buf;
284 }
285 
286 static char *arc_extn_mumbojumbo(int cpu_id, char *buf, int len)
287 {
288 	int n = 0;
289 	struct cpuinfo_arc *cpu = &cpuinfo_arc700[cpu_id];
290 
291 	FIX_PTR(cpu);
292 
293 	n += scnprintf(buf + n, len - n, "Vector Table\t: %#x\n", cpu->vec_base);
294 
295 	if (cpu->extn.fpu_sp || cpu->extn.fpu_dp)
296 		n += scnprintf(buf + n, len - n, "FPU\t\t: %s%s\n",
297 			       IS_AVAIL1(cpu->extn.fpu_sp, "SP "),
298 			       IS_AVAIL1(cpu->extn.fpu_dp, "DP "));
299 
300 	if (cpu->extn.debug)
301 		n += scnprintf(buf + n, len - n, "DEBUG\t\t: %s%s%s\n",
302 			       IS_AVAIL1(cpu->extn.ap, "ActionPoint "),
303 			       IS_AVAIL1(cpu->extn.smart, "smaRT "),
304 			       IS_AVAIL1(cpu->extn.rtt, "RTT "));
305 
306 	if (cpu->dccm.sz || cpu->iccm.sz)
307 		n += scnprintf(buf + n, len - n, "Extn [CCM]\t: DCCM @ %x, %d KB / ICCM: @ %x, %d KB\n",
308 			       cpu->dccm.base_addr, TO_KB(cpu->dccm.sz),
309 			       cpu->iccm.base_addr, TO_KB(cpu->iccm.sz));
310 
311 	n += scnprintf(buf + n, len - n, "OS ABI [v%d]\t: %s\n",
312 			EF_ARC_OSABI_CURRENT >> 8,
313 			EF_ARC_OSABI_CURRENT == EF_ARC_OSABI_V3 ?
314 			"no-legacy-syscalls" : "64-bit data any register aligned");
315 
316 	return buf;
317 }
318 
319 static void arc_chk_core_config(void)
320 {
321 	struct cpuinfo_arc *cpu = &cpuinfo_arc700[smp_processor_id()];
322 	int saved = 0, present = 0;
323 	char *opt_nm = NULL;;
324 
325 	if (!cpu->extn.timer0)
326 		panic("Timer0 is not present!\n");
327 
328 	if (!cpu->extn.timer1)
329 		panic("Timer1 is not present!\n");
330 
331 #ifdef CONFIG_ARC_HAS_DCCM
332 	/*
333 	 * DCCM can be arbit placed in hardware.
334 	 * Make sure it's placement/sz matches what Linux is built with
335 	 */
336 	if ((unsigned int)__arc_dccm_base != cpu->dccm.base_addr)
337 		panic("Linux built with incorrect DCCM Base address\n");
338 
339 	if (CONFIG_ARC_DCCM_SZ != cpu->dccm.sz)
340 		panic("Linux built with incorrect DCCM Size\n");
341 #endif
342 
343 #ifdef CONFIG_ARC_HAS_ICCM
344 	if (CONFIG_ARC_ICCM_SZ != cpu->iccm.sz)
345 		panic("Linux built with incorrect ICCM Size\n");
346 #endif
347 
348 	/*
349 	 * FP hardware/software config sanity
350 	 * -If hardware present, kernel needs to save/restore FPU state
351 	 * -If not, it will crash trying to save/restore the non-existant regs
352 	 */
353 
354 	if (is_isa_arcompact()) {
355 		opt_nm = "CONFIG_ARC_FPU_SAVE_RESTORE";
356 		saved = IS_ENABLED(CONFIG_ARC_FPU_SAVE_RESTORE);
357 
358 		/* only DPDP checked since SP has no arch visible regs */
359 		present = cpu->extn.fpu_dp;
360 	} else {
361 		opt_nm = "CONFIG_ARC_HAS_ACCL_REGS";
362 		saved = IS_ENABLED(CONFIG_ARC_HAS_ACCL_REGS);
363 
364 		/* Accumulator Low:High pair (r58:59) present if DSP MPY or FPU */
365 		present = cpu->extn_mpy.dsp | cpu->extn.fpu_sp | cpu->extn.fpu_dp;
366 	}
367 
368 	if (present && !saved)
369 		pr_warn("Enable %s for working apps\n", opt_nm);
370 	else if (!present && saved)
371 		panic("Disable %s, hardware NOT present\n", opt_nm);
372 }
373 
374 /*
375  * Initialize and setup the processor core
376  * This is called by all the CPUs thus should not do special case stuff
377  *    such as only for boot CPU etc
378  */
379 
380 void setup_processor(void)
381 {
382 	char str[512];
383 	int cpu_id = smp_processor_id();
384 
385 	read_arc_build_cfg_regs();
386 	arc_init_IRQ();
387 
388 	printk(arc_cpu_mumbojumbo(cpu_id, str, sizeof(str)));
389 
390 	arc_mmu_init();
391 	arc_cache_init();
392 
393 	printk(arc_extn_mumbojumbo(cpu_id, str, sizeof(str)));
394 	printk(arc_platform_smp_cpuinfo());
395 
396 	arc_chk_core_config();
397 }
398 
399 static inline int is_kernel(unsigned long addr)
400 {
401 	if (addr >= (unsigned long)_stext && addr <= (unsigned long)_end)
402 		return 1;
403 	return 0;
404 }
405 
406 void __init setup_arch(char **cmdline_p)
407 {
408 #ifdef CONFIG_ARC_UBOOT_SUPPORT
409 	/* make sure that uboot passed pointer to cmdline/dtb is valid */
410 	if (uboot_tag && is_kernel((unsigned long)uboot_arg))
411 		panic("Invalid uboot arg\n");
412 
413 	/* See if u-boot passed an external Device Tree blob */
414 	machine_desc = setup_machine_fdt(uboot_arg);	/* uboot_tag == 2 */
415 	if (!machine_desc)
416 #endif
417 	{
418 		/* No, so try the embedded one */
419 		machine_desc = setup_machine_fdt(__dtb_start);
420 		if (!machine_desc)
421 			panic("Embedded DT invalid\n");
422 
423 		/*
424 		 * If we are here, it is established that @uboot_arg didn't
425 		 * point to DT blob. Instead if u-boot says it is cmdline,
426 		 * append to embedded DT cmdline.
427 		 * setup_machine_fdt() would have populated @boot_command_line
428 		 */
429 		if (uboot_tag == 1) {
430 			/* Ensure a whitespace between the 2 cmdlines */
431 			strlcat(boot_command_line, " ", COMMAND_LINE_SIZE);
432 			strlcat(boot_command_line, uboot_arg,
433 				COMMAND_LINE_SIZE);
434 		}
435 	}
436 
437 	/* Save unparsed command line copy for /proc/cmdline */
438 	*cmdline_p = boot_command_line;
439 
440 	/* To force early parsing of things like mem=xxx */
441 	parse_early_param();
442 
443 	/* Platform/board specific: e.g. early console registration */
444 	if (machine_desc->init_early)
445 		machine_desc->init_early();
446 
447 	smp_init_cpus();
448 
449 	setup_processor();
450 	setup_arch_memory();
451 
452 	/* copy flat DT out of .init and then unflatten it */
453 	unflatten_and_copy_device_tree();
454 
455 	/* Can be issue if someone passes cmd line arg "ro"
456 	 * But that is unlikely so keeping it as it is
457 	 */
458 	root_mountflags &= ~MS_RDONLY;
459 
460 #if defined(CONFIG_VT) && defined(CONFIG_DUMMY_CONSOLE)
461 	conswitchp = &dummy_con;
462 #endif
463 
464 	arc_unwind_init();
465 }
466 
467 /*
468  * Called from start_kernel() - boot CPU only
469  */
470 void __init time_init(void)
471 {
472 	of_clk_init(NULL);
473 	clocksource_probe();
474 }
475 
476 static int __init customize_machine(void)
477 {
478 	if (machine_desc->init_machine)
479 		machine_desc->init_machine();
480 
481 	return 0;
482 }
483 arch_initcall(customize_machine);
484 
485 static int __init init_late_machine(void)
486 {
487 	if (machine_desc->init_late)
488 		machine_desc->init_late();
489 
490 	return 0;
491 }
492 late_initcall(init_late_machine);
493 /*
494  *  Get CPU information for use by the procfs.
495  */
496 
497 #define cpu_to_ptr(c)	((void *)(0xFFFF0000 | (unsigned int)(c)))
498 #define ptr_to_cpu(p)	(~0xFFFF0000UL & (unsigned int)(p))
499 
500 static int show_cpuinfo(struct seq_file *m, void *v)
501 {
502 	char *str;
503 	int cpu_id = ptr_to_cpu(v);
504 	struct device *cpu_dev = get_cpu_device(cpu_id);
505 	struct clk *cpu_clk;
506 	unsigned long freq = 0;
507 
508 	if (!cpu_online(cpu_id)) {
509 		seq_printf(m, "processor [%d]\t: Offline\n", cpu_id);
510 		goto done;
511 	}
512 
513 	str = (char *)__get_free_page(GFP_TEMPORARY);
514 	if (!str)
515 		goto done;
516 
517 	seq_printf(m, arc_cpu_mumbojumbo(cpu_id, str, PAGE_SIZE));
518 
519 	cpu_clk = clk_get(cpu_dev, NULL);
520 	if (IS_ERR(cpu_clk)) {
521 		seq_printf(m, "CPU speed \t: Cannot get clock for processor [%d]\n",
522 			   cpu_id);
523 	} else {
524 		freq = clk_get_rate(cpu_clk);
525 	}
526 	if (freq)
527 		seq_printf(m, "CPU speed\t: %lu.%02lu Mhz\n",
528 			   freq / 1000000, (freq / 10000) % 100);
529 
530 	seq_printf(m, "Bogo MIPS\t: %lu.%02lu\n",
531 		   loops_per_jiffy / (500000 / HZ),
532 		   (loops_per_jiffy / (5000 / HZ)) % 100);
533 
534 	seq_printf(m, arc_mmu_mumbojumbo(cpu_id, str, PAGE_SIZE));
535 	seq_printf(m, arc_cache_mumbojumbo(cpu_id, str, PAGE_SIZE));
536 	seq_printf(m, arc_extn_mumbojumbo(cpu_id, str, PAGE_SIZE));
537 	seq_printf(m, arc_platform_smp_cpuinfo());
538 
539 	free_page((unsigned long)str);
540 done:
541 	seq_printf(m, "\n");
542 
543 	return 0;
544 }
545 
546 static void *c_start(struct seq_file *m, loff_t *pos)
547 {
548 	/*
549 	 * Callback returns cpu-id to iterator for show routine, NULL to stop.
550 	 * However since NULL is also a valid cpu-id (0), we use a round-about
551 	 * way to pass it w/o having to kmalloc/free a 2 byte string.
552 	 * Encode cpu-id as 0xFFcccc, which is decoded by show routine.
553 	 */
554 	return *pos < nr_cpu_ids ? cpu_to_ptr(*pos) : NULL;
555 }
556 
557 static void *c_next(struct seq_file *m, void *v, loff_t *pos)
558 {
559 	++*pos;
560 	return c_start(m, pos);
561 }
562 
563 static void c_stop(struct seq_file *m, void *v)
564 {
565 }
566 
567 const struct seq_operations cpuinfo_op = {
568 	.start	= c_start,
569 	.next	= c_next,
570 	.stop	= c_stop,
571 	.show	= show_cpuinfo
572 };
573 
574 static DEFINE_PER_CPU(struct cpu, cpu_topology);
575 
576 static int __init topology_init(void)
577 {
578 	int cpu;
579 
580 	for_each_present_cpu(cpu)
581 	    register_cpu(&per_cpu(cpu_topology, cpu), cpu);
582 
583 	return 0;
584 }
585 
586 subsys_initcall(topology_init);
587