1 // SPDX-License-Identifier: GPL-2.0
2 #include <linux/linkage.h>
3 #include <linux/errno.h>
4 #include <linux/signal.h>
5 #include <linux/sched.h>
6 #include <linux/ioport.h>
7 #include <linux/interrupt.h>
8 #include <linux/irq.h>
9 #include <linux/timex.h>
10 #include <linux/random.h>
11 #include <linux/init.h>
12 #include <linux/kernel_stat.h>
13 #include <linux/syscore_ops.h>
14 #include <linux/bitops.h>
15 #include <linux/acpi.h>
16 #include <linux/io.h>
17 #include <linux/delay.h>
18 #include <linux/pgtable.h>
19
20 #include <linux/atomic.h>
21 #include <asm/timer.h>
22 #include <asm/hw_irq.h>
23 #include <asm/desc.h>
24 #include <asm/apic.h>
25 #include <asm/i8259.h>
26
27 /*
28 * This is the 'legacy' 8259A Programmable Interrupt Controller,
29 * present in the majority of PC/AT boxes.
30 * plus some generic x86 specific things if generic specifics makes
31 * any sense at all.
32 */
33 static void init_8259A(int auto_eoi);
34
35 static bool pcat_compat __ro_after_init;
36 static int i8259A_auto_eoi;
37 DEFINE_RAW_SPINLOCK(i8259A_lock);
38
39 /*
40 * 8259A PIC functions to handle ISA devices:
41 */
42
43 /*
44 * This contains the irq mask for both 8259A irq controllers,
45 */
46 unsigned int cached_irq_mask = 0xffff;
47
48 /*
49 * Not all IRQs can be routed through the IO-APIC, eg. on certain (older)
50 * boards the timer interrupt is not really connected to any IO-APIC pin,
51 * it's fed to the master 8259A's IR0 line only.
52 *
53 * Any '1' bit in this mask means the IRQ is routed through the IO-APIC.
54 * this 'mixed mode' IRQ handling costs nothing because it's only used
55 * at IRQ setup time.
56 */
57 unsigned long io_apic_irqs;
58
59 static void mask_8259A_irq(unsigned int irq)
60 {
61 unsigned int mask = 1 << irq;
62 unsigned long flags;
63
64 raw_spin_lock_irqsave(&i8259A_lock, flags);
65 cached_irq_mask |= mask;
66 if (irq & 8)
67 outb(cached_slave_mask, PIC_SLAVE_IMR);
68 else
69 outb(cached_master_mask, PIC_MASTER_IMR);
70 raw_spin_unlock_irqrestore(&i8259A_lock, flags);
71 }
72
73 static void disable_8259A_irq(struct irq_data *data)
74 {
75 mask_8259A_irq(data->irq);
76 }
77
78 static void unmask_8259A_irq(unsigned int irq)
79 {
80 unsigned int mask = ~(1 << irq);
81 unsigned long flags;
82
83 raw_spin_lock_irqsave(&i8259A_lock, flags);
84 cached_irq_mask &= mask;
85 if (irq & 8)
86 outb(cached_slave_mask, PIC_SLAVE_IMR);
87 else
88 outb(cached_master_mask, PIC_MASTER_IMR);
89 raw_spin_unlock_irqrestore(&i8259A_lock, flags);
90 }
91
92 static void enable_8259A_irq(struct irq_data *data)
93 {
94 unmask_8259A_irq(data->irq);
95 }
96
97 static int i8259A_irq_pending(unsigned int irq)
98 {
99 unsigned int mask = 1<<irq;
100 unsigned long flags;
101 int ret;
102
103 raw_spin_lock_irqsave(&i8259A_lock, flags);
104 if (irq < 8)
105 ret = inb(PIC_MASTER_CMD) & mask;
106 else
107 ret = inb(PIC_SLAVE_CMD) & (mask >> 8);
108 raw_spin_unlock_irqrestore(&i8259A_lock, flags);
109
110 return ret;
111 }
112
113 static void make_8259A_irq(unsigned int irq)
114 {
115 disable_irq_nosync(irq);
116 io_apic_irqs &= ~(1<<irq);
117 irq_set_chip_and_handler(irq, &i8259A_chip, handle_level_irq);
118 irq_set_status_flags(irq, IRQ_LEVEL);
119 enable_irq(irq);
120 lapic_assign_legacy_vector(irq, true);
121 }
122
123 /*
124 * This function assumes to be called rarely. Switching between
125 * 8259A registers is slow.
126 * This has to be protected by the irq controller spinlock
127 * before being called.
128 */
129 static inline int i8259A_irq_real(unsigned int irq)
130 {
131 int value;
132 int irqmask = 1<<irq;
133
134 if (irq < 8) {
135 outb(0x0B, PIC_MASTER_CMD); /* ISR register */
136 value = inb(PIC_MASTER_CMD) & irqmask;
137 outb(0x0A, PIC_MASTER_CMD); /* back to the IRR register */
138 return value;
139 }
140 outb(0x0B, PIC_SLAVE_CMD); /* ISR register */
141 value = inb(PIC_SLAVE_CMD) & (irqmask >> 8);
142 outb(0x0A, PIC_SLAVE_CMD); /* back to the IRR register */
143 return value;
144 }
145
146 /*
147 * Careful! The 8259A is a fragile beast, it pretty
148 * much _has_ to be done exactly like this (mask it
149 * first, _then_ send the EOI, and the order of EOI
150 * to the two 8259s is important!
151 */
152 static void mask_and_ack_8259A(struct irq_data *data)
153 {
154 unsigned int irq = data->irq;
155 unsigned int irqmask = 1 << irq;
156 unsigned long flags;
157
158 raw_spin_lock_irqsave(&i8259A_lock, flags);
159 /*
160 * Lightweight spurious IRQ detection. We do not want
161 * to overdo spurious IRQ handling - it's usually a sign
162 * of hardware problems, so we only do the checks we can
163 * do without slowing down good hardware unnecessarily.
164 *
165 * Note that IRQ7 and IRQ15 (the two spurious IRQs
166 * usually resulting from the 8259A-1|2 PICs) occur
167 * even if the IRQ is masked in the 8259A. Thus we
168 * can check spurious 8259A IRQs without doing the
169 * quite slow i8259A_irq_real() call for every IRQ.
170 * This does not cover 100% of spurious interrupts,
171 * but should be enough to warn the user that there
172 * is something bad going on ...
173 */
174 if (cached_irq_mask & irqmask)
175 goto spurious_8259A_irq;
176 cached_irq_mask |= irqmask;
177
178 handle_real_irq:
179 if (irq & 8) {
180 inb(PIC_SLAVE_IMR); /* DUMMY - (do we need this?) */
181 outb(cached_slave_mask, PIC_SLAVE_IMR);
182 /* 'Specific EOI' to slave */
183 outb(0x60+(irq&7), PIC_SLAVE_CMD);
184 /* 'Specific EOI' to master-IRQ2 */
185 outb(0x60+PIC_CASCADE_IR, PIC_MASTER_CMD);
186 } else {
187 inb(PIC_MASTER_IMR); /* DUMMY - (do we need this?) */
188 outb(cached_master_mask, PIC_MASTER_IMR);
189 outb(0x60+irq, PIC_MASTER_CMD); /* 'Specific EOI to master */
190 }
191 raw_spin_unlock_irqrestore(&i8259A_lock, flags);
192 return;
193
194 spurious_8259A_irq:
195 /*
196 * this is the slow path - should happen rarely.
197 */
198 if (i8259A_irq_real(irq))
199 /*
200 * oops, the IRQ _is_ in service according to the
201 * 8259A - not spurious, go handle it.
202 */
203 goto handle_real_irq;
204
205 {
206 static int spurious_irq_mask;
207 /*
208 * At this point we can be sure the IRQ is spurious,
209 * lets ACK and report it. [once per IRQ]
210 */
211 if (!(spurious_irq_mask & irqmask)) {
212 printk_deferred(KERN_DEBUG
213 "spurious 8259A interrupt: IRQ%d.\n", irq);
214 spurious_irq_mask |= irqmask;
215 }
216 atomic_inc(&irq_err_count);
217 /*
218 * Theoretically we do not have to handle this IRQ,
219 * but in Linux this does not cause problems and is
220 * simpler for us.
221 */
222 goto handle_real_irq;
223 }
224 }
225
226 struct irq_chip i8259A_chip = {
227 .name = "XT-PIC",
228 .irq_mask = disable_8259A_irq,
229 .irq_disable = disable_8259A_irq,
230 .irq_unmask = enable_8259A_irq,
231 .irq_mask_ack = mask_and_ack_8259A,
232 };
233
234 static char irq_trigger[2];
235 /* ELCR registers (0x4d0, 0x4d1) control edge/level of IRQ */
236 static void restore_ELCR(char *trigger)
237 {
238 outb(trigger[0], PIC_ELCR1);
239 outb(trigger[1], PIC_ELCR2);
240 }
241
242 static void save_ELCR(char *trigger)
243 {
244 /* IRQ 0,1,2,8,13 are marked as reserved */
245 trigger[0] = inb(PIC_ELCR1) & 0xF8;
246 trigger[1] = inb(PIC_ELCR2) & 0xDE;
247 }
248
249 static void i8259A_resume(void)
250 {
251 init_8259A(i8259A_auto_eoi);
252 restore_ELCR(irq_trigger);
253 }
254
255 static int i8259A_suspend(void)
256 {
257 save_ELCR(irq_trigger);
258 return 0;
259 }
260
261 static void i8259A_shutdown(void)
262 {
263 /* Put the i8259A into a quiescent state that
264 * the kernel initialization code can get it
265 * out of.
266 */
267 outb(0xff, PIC_MASTER_IMR); /* mask all of 8259A-1 */
268 outb(0xff, PIC_SLAVE_IMR); /* mask all of 8259A-2 */
269 }
270
271 static struct syscore_ops i8259_syscore_ops = {
272 .suspend = i8259A_suspend,
273 .resume = i8259A_resume,
274 .shutdown = i8259A_shutdown,
275 };
276
277 static void mask_8259A(void)
278 {
279 unsigned long flags;
280
281 raw_spin_lock_irqsave(&i8259A_lock, flags);
282
283 outb(0xff, PIC_MASTER_IMR); /* mask all of 8259A-1 */
284 outb(0xff, PIC_SLAVE_IMR); /* mask all of 8259A-2 */
285
286 raw_spin_unlock_irqrestore(&i8259A_lock, flags);
287 }
288
289 static void unmask_8259A(void)
290 {
291 unsigned long flags;
292
293 raw_spin_lock_irqsave(&i8259A_lock, flags);
294
295 outb(cached_master_mask, PIC_MASTER_IMR); /* restore master IRQ mask */
296 outb(cached_slave_mask, PIC_SLAVE_IMR); /* restore slave IRQ mask */
297
298 raw_spin_unlock_irqrestore(&i8259A_lock, flags);
299 }
300
301 static int probe_8259A(void)
302 {
303 unsigned char new_val, probe_val = ~(1 << PIC_CASCADE_IR);
304 unsigned long flags;
305
306 /*
307 * If MADT has the PCAT_COMPAT flag set, then do not bother probing
308 * for the PIC. Some BIOSes leave the PIC uninitialized and probing
309 * fails.
310 *
311 * Right now this causes problems as quite some code depends on
312 * nr_legacy_irqs() > 0 or has_legacy_pic() == true. This is silly
313 * when the system has an IO/APIC because then PIC is not required
314 * at all, except for really old machines where the timer interrupt
315 * must be routed through the PIC. So just pretend that the PIC is
316 * there and let legacy_pic->init() initialize it for nothing.
317 *
318 * Alternatively this could just try to initialize the PIC and
319 * repeat the probe, but for cases where there is no PIC that's
320 * just pointless.
321 */
322 if (pcat_compat)
323 return nr_legacy_irqs();
324
325 /*
326 * Check to see if we have a PIC. Mask all except the cascade and
327 * read back the value we just wrote. If we don't have a PIC, we
328 * will read 0xff as opposed to the value we wrote.
329 */
330 raw_spin_lock_irqsave(&i8259A_lock, flags);
331
332 outb(0xff, PIC_SLAVE_IMR); /* mask all of 8259A-2 */
333 outb(probe_val, PIC_MASTER_IMR);
334 new_val = inb(PIC_MASTER_IMR);
335 if (new_val != probe_val) {
336 printk(KERN_INFO "Using NULL legacy PIC\n");
337 legacy_pic = &null_legacy_pic;
338 }
339
340 raw_spin_unlock_irqrestore(&i8259A_lock, flags);
341 return nr_legacy_irqs();
342 }
343
344 static void init_8259A(int auto_eoi)
345 {
346 unsigned long flags;
347
348 i8259A_auto_eoi = auto_eoi;
349
350 raw_spin_lock_irqsave(&i8259A_lock, flags);
351
352 outb(0xff, PIC_MASTER_IMR); /* mask all of 8259A-1 */
353
354 /*
355 * outb_pic - this has to work on a wide range of PC hardware.
356 */
357 outb_pic(0x11, PIC_MASTER_CMD); /* ICW1: select 8259A-1 init */
358
359 /* ICW2: 8259A-1 IR0-7 mapped to ISA_IRQ_VECTOR(0) */
360 outb_pic(ISA_IRQ_VECTOR(0), PIC_MASTER_IMR);
361
362 /* 8259A-1 (the master) has a slave on IR2 */
363 outb_pic(1U << PIC_CASCADE_IR, PIC_MASTER_IMR);
364
365 if (auto_eoi) /* master does Auto EOI */
366 outb_pic(MASTER_ICW4_DEFAULT | PIC_ICW4_AEOI, PIC_MASTER_IMR);
367 else /* master expects normal EOI */
368 outb_pic(MASTER_ICW4_DEFAULT, PIC_MASTER_IMR);
369
370 outb_pic(0x11, PIC_SLAVE_CMD); /* ICW1: select 8259A-2 init */
371
372 /* ICW2: 8259A-2 IR0-7 mapped to ISA_IRQ_VECTOR(8) */
373 outb_pic(ISA_IRQ_VECTOR(8), PIC_SLAVE_IMR);
374 /* 8259A-2 is a slave on master's IR2 */
375 outb_pic(PIC_CASCADE_IR, PIC_SLAVE_IMR);
376 /* (slave's support for AEOI in flat mode is to be investigated) */
377 outb_pic(SLAVE_ICW4_DEFAULT, PIC_SLAVE_IMR);
378
379 if (auto_eoi)
380 /*
381 * In AEOI mode we just have to mask the interrupt
382 * when acking.
383 */
384 i8259A_chip.irq_mask_ack = disable_8259A_irq;
385 else
386 i8259A_chip.irq_mask_ack = mask_and_ack_8259A;
387
388 udelay(100); /* wait for 8259A to initialize */
389
390 outb(cached_master_mask, PIC_MASTER_IMR); /* restore master IRQ mask */
391 outb(cached_slave_mask, PIC_SLAVE_IMR); /* restore slave IRQ mask */
392
393 raw_spin_unlock_irqrestore(&i8259A_lock, flags);
394 }
395
396 /*
397 * make i8259 a driver so that we can select pic functions at run time. the goal
398 * is to make x86 binary compatible among pc compatible and non-pc compatible
399 * platforms, such as x86 MID.
400 */
401
402 static void legacy_pic_noop(void) { };
403 static void legacy_pic_uint_noop(unsigned int unused) { };
404 static void legacy_pic_int_noop(int unused) { };
405 static int legacy_pic_irq_pending_noop(unsigned int irq)
406 {
407 return 0;
408 }
409 static int legacy_pic_probe(void)
410 {
411 return 0;
412 }
413
414 struct legacy_pic null_legacy_pic = {
415 .nr_legacy_irqs = 0,
416 .chip = &dummy_irq_chip,
417 .mask = legacy_pic_uint_noop,
418 .unmask = legacy_pic_uint_noop,
419 .mask_all = legacy_pic_noop,
420 .restore_mask = legacy_pic_noop,
421 .init = legacy_pic_int_noop,
422 .probe = legacy_pic_probe,
423 .irq_pending = legacy_pic_irq_pending_noop,
424 .make_irq = legacy_pic_uint_noop,
425 };
426
427 static struct legacy_pic default_legacy_pic = {
428 .nr_legacy_irqs = NR_IRQS_LEGACY,
429 .chip = &i8259A_chip,
430 .mask = mask_8259A_irq,
431 .unmask = unmask_8259A_irq,
432 .mask_all = mask_8259A,
433 .restore_mask = unmask_8259A,
434 .init = init_8259A,
435 .probe = probe_8259A,
436 .irq_pending = i8259A_irq_pending,
437 .make_irq = make_8259A_irq,
438 };
439
440 struct legacy_pic *legacy_pic = &default_legacy_pic;
441 EXPORT_SYMBOL(legacy_pic);
442
443 static int __init i8259A_init_ops(void)
444 {
445 if (legacy_pic == &default_legacy_pic)
446 register_syscore_ops(&i8259_syscore_ops);
447
448 return 0;
449 }
450 device_initcall(i8259A_init_ops);
451
452 void __init legacy_pic_pcat_compat(void)
453 {
454 pcat_compat = true;
455 }
456
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