arch/x86/kernel/i8259.c

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