arch/m68k/mac/macints.c

   1 /*
   2  *      Macintosh interrupts
   3  *
   4  * General design:
   5  * In contrary to the Amiga and Atari platforms, the Mac hardware seems to
   6  * exclusively use the autovector interrupts (the 'generic level0-level7'
   7  * interrupts with exception vectors 0x19-0x1f). The following interrupt levels
   8  * are used:
   9  *      1       - VIA1
  10  *                - slot 0: one second interrupt (CA2)
  11  *                - slot 1: VBlank (CA1)
  12  *                - slot 2: ADB data ready (SR full)
  13  *                - slot 3: ADB data  (CB2)
  14  *                - slot 4: ADB clock (CB1)
  15  *                - slot 5: timer 2
  16  *                - slot 6: timer 1
  17  *                - slot 7: status of IRQ; signals 'any enabled int.'
  18  *
  19  *      2       - VIA2 or RBV
  20  *                - slot 0: SCSI DRQ (CA2)
  21  *                - slot 1: NUBUS IRQ (CA1) need to read port A to find which
  22  *                - slot 2: /EXP IRQ (only on IIci)
  23  *                - slot 3: SCSI IRQ (CB2)
  24  *                - slot 4: ASC IRQ (CB1)
  25  *                - slot 5: timer 2 (not on IIci)
  26  *                - slot 6: timer 1 (not on IIci)
  27  *                - slot 7: status of IRQ; signals 'any enabled int.'
  28  *
  29  *      2       - OSS (IIfx only?)
  30  *                - slot 0: SCSI interrupt
  31  *                - slot 1: Sound interrupt
  32  *
  33  * Levels 3-6 vary by machine type. For VIA or RBV Macintoshes:
  34  *
  35  *      3       - unused (?)
  36  *
  37  *      4       - SCC (slot number determined by reading RR3 on the SSC itself)
  38  *                - slot 1: SCC channel A
  39  *                - slot 2: SCC channel B
  40  *
  41  *      5       - unused (?)
  42  *                [serial errors or special conditions seem to raise level 6
  43  *                interrupts on some models (LC4xx?)]
  44  *
  45  *      6       - off switch (?)
  46  *
  47  * For OSS Macintoshes (IIfx only at this point):
  48  *
  49  *      3       - Nubus interrupt
  50  *                - slot 0: Slot $9
  51  *                - slot 1: Slot $A
  52  *                - slot 2: Slot $B
  53  *                - slot 3: Slot $C
  54  *                - slot 4: Slot $D
  55  *                - slot 5: Slot $E
  56  *
  57  *      4       - SCC IOP
  58  *                - slot 1: SCC channel A
  59  *                - slot 2: SCC channel B
  60  *
  61  *      5       - ISM IOP (ADB?)
  62  *
  63  *      6       - unused
  64  *
  65  * For PSC Macintoshes (660AV, 840AV):
  66  *
  67  *      3       - PSC level 3
  68  *                - slot 0: MACE
  69  *
  70  *      4       - PSC level 4
  71  *                - slot 1: SCC channel A interrupt
  72  *                - slot 2: SCC channel B interrupt
  73  *                - slot 3: MACE DMA
  74  *
  75  *      5       - PSC level 5
  76  *
  77  *      6       - PSC level 6
  78  *
  79  * Finally we have good 'ole level 7, the non-maskable interrupt:
  80  *
  81  *      7       - NMI (programmer's switch on the back of some Macs)
  82  *                Also RAM parity error on models which support it (IIc, IIfx?)
  83  *
  84  * The current interrupt logic looks something like this:
  85  *
  86  * - We install dispatchers for the autovector interrupts (1-7). These
  87  *   dispatchers are responsible for querying the hardware (the
  88  *   VIA/RBV/OSS/PSC chips) to determine the actual interrupt source. Using
  89  *   this information a machspec interrupt number is generated by placing the
  90  *   index of the interrupt hardware into the low three bits and the original
  91  *   autovector interrupt number in the upper 5 bits. The handlers for the
  92  *   resulting machspec interrupt are then called.
  93  *
  94  * - Nubus is a special case because its interrupts are hidden behind two
  95  *   layers of hardware. Nubus interrupts come in as index 1 on VIA #2,
  96  *   which translates to IRQ number 17. In this spot we install _another_
  97  *   dispatcher. This dispatcher finds the interrupting slot number (9-F) and
  98  *   then forms a new machspec interrupt number as above with the slot number
  99  *   minus 9 in the low three bits and the pseudo-level 7 in the upper five
 100  *   bits.  The handlers for this new machspec interrupt number are then
 101  *   called. This puts Nubus interrupts into the range 56-62.
 102  *
 103  * - The Baboon interrupts (used on some PowerBooks) are an even more special
 104  *   case. They're hidden behind the Nubus slot $C interrupt thus adding a
 105  *   third layer of indirection. Why oh why did the Apple engineers do that?
 106  *
 107  * - We support "fast" and "slow" handlers, just like the Amiga port. The
 108  *   fast handlers are called first and with all interrupts disabled. They
 109  *   are expected to execute quickly (hence the name). The slow handlers are
 110  *   called last with interrupts enabled and the interrupt level restored.
 111  *   They must therefore be reentrant.
 112  *
 113  *   TODO:
 114  *
 115  */
 116
 117 #include <linux/types.h>
 118 #include <linux/kernel.h>
 119 #include <linux/sched.h>
 120 #include <linux/kernel_stat.h>
 121 #include <linux/interrupt.h> /* for intr_count */
 122 #include <linux/delay.h>
 123 #include <linux/seq_file.h>
 124
 125 #include <asm/system.h>
 126 #include <asm/irq.h>
 127 #include <asm/traps.h>
 128 #include <asm/bootinfo.h>
 129 #include <asm/machw.h>
 130 #include <asm/macintosh.h>
 131 #include <asm/mac_via.h>
 132 #include <asm/mac_psc.h>
 133 #include <asm/hwtest.h>
 134 #include <asm/errno.h>
 135 #include <asm/macints.h>
 136
 137 #define DEBUG_SPURIOUS
 138 #define SHUTUP_SONIC
 139
 140 /*
 141  * The mac_irq_list array is an array of linked lists of irq_node_t nodes.
 142  * Each node contains one handler to be called whenever the interrupt
 143  * occurs, with fast handlers listed before slow handlers.
 144  */
 145
 146 irq_node_t *mac_irq_list[NUM_MAC_SOURCES];
 147
 148 /* SCC interrupt mask */
 149
 150 static int scc_mask;
 151
 152 /*
 153  * VIA/RBV hooks
 154  */
 155
 156 extern void via_init(void);
 157 extern void via_register_interrupts(void);
 158 extern void via_irq_enable(int);
 159 extern void via_irq_disable(int);
 160 extern void via_irq_clear(int);
 161 extern int  via_irq_pending(int);
 162
 163 /*
 164  * OSS hooks
 165  */
 166
 167 extern int oss_present;
 168
 169 extern void oss_init(void);
 170 extern void oss_register_interrupts(void);
 171 extern void oss_irq_enable(int);
 172 extern void oss_irq_disable(int);
 173 extern void oss_irq_clear(int);
 174 extern int  oss_irq_pending(int);
 175
 176 /*
 177  * PSC hooks
 178  */
 179
 180 extern int psc_present;
 181
 182 extern void psc_init(void);
 183 extern void psc_register_interrupts(void);
 184 extern void psc_irq_enable(int);
 185 extern void psc_irq_disable(int);
 186 extern void psc_irq_clear(int);
 187 extern int  psc_irq_pending(int);
 188
 189 /*
 190  * IOP hooks
 191  */
 192
 193 extern void iop_register_interrupts(void);
 194
 195 /*
 196  * Baboon hooks
 197  */
 198
 199 extern int baboon_present;
 200
 201 extern void baboon_init(void);
 202 extern void baboon_register_interrupts(void);
 203 extern void baboon_irq_enable(int);
 204 extern void baboon_irq_disable(int);
 205 extern void baboon_irq_clear(int);
 206 extern int  baboon_irq_pending(int);
 207
 208 /*
 209  * SCC interrupt routines
 210  */
 211
 212 static void scc_irq_enable(int);
 213 static void scc_irq_disable(int);
 214
 215 /*
 216  * console_loglevel determines NMI handler function
 217  */
 218
 219 extern irqreturn_t mac_bang(int, void *, struct pt_regs *);
 220 irqreturn_t mac_nmi_handler(int, void *, struct pt_regs *);
 221 irqreturn_t mac_debug_handler(int, void *, struct pt_regs *);
 222
 223 /* #define DEBUG_MACINTS */
 224
 225 void mac_init_IRQ(void)
 226 {
 227         int i;
 228
 229 #ifdef DEBUG_MACINTS
 230         printk("mac_init_IRQ(): Setting things up...\n");
 231 #endif
 232         /* Initialize the IRQ handler lists. Initially each list is empty, */
 233
 234         for (i = 0; i < NUM_MAC_SOURCES; i++) {
 235                 mac_irq_list[i] = NULL;
 236         }
 237
 238         scc_mask = 0;
 239
 240         /* Make sure the SONIC interrupt is cleared or things get ugly */
 241 #ifdef SHUTUP_SONIC
 242         printk("Killing onboard sonic... ");
 243         /* This address should hopefully be mapped already */
 244         if (hwreg_present((void*)(0x50f0a000))) {
 245                 *(long *)(0x50f0a014) = 0x7fffL;
 246                 *(long *)(0x50f0a010) = 0L;
 247         }
 248         printk("Done.\n");
 249 #endif /* SHUTUP_SONIC */
 250
 251         /*
 252          * Now register the handlers for the master IRQ handlers
 253          * at levels 1-7. Most of the work is done elsewhere.
 254          */
 255
 256         if (oss_present) {
 257                 oss_register_interrupts();
 258         } else {
 259                 via_register_interrupts();
 260         }
 261         if (psc_present) psc_register_interrupts();
 262         if (baboon_present) baboon_register_interrupts();
 263         iop_register_interrupts();
 264         cpu_request_irq(7, mac_nmi_handler, IRQ_FLG_LOCK, "NMI",
 265                         mac_nmi_handler);
 266 #ifdef DEBUG_MACINTS
 267         printk("mac_init_IRQ(): Done!\n");
 268 #endif
 269 }
 270
 271 /*
 272  * Routines to work with irq_node_t's on linked lists lifted from
 273  * the Amiga code written by Roman Zippel.
 274  */
 275
 276 static inline void mac_insert_irq(irq_node_t **list, irq_node_t *node)
 277 {
 278         unsigned long flags;
 279         irq_node_t *cur;
 280
 281         if (!node->dev_id)
 282                 printk("%s: Warning: dev_id of %s is zero\n",
 283                        __FUNCTION__, node->devname);
 284
 285         local_irq_save(flags);
 286
 287         cur = *list;
 288
 289         if (node->flags & IRQ_FLG_FAST) {
 290                 node->flags &= ~IRQ_FLG_SLOW;
 291                 while (cur && cur->flags & IRQ_FLG_FAST) {
 292                         list = &cur->next;
 293                         cur = cur->next;
 294                 }
 295         } else if (node->flags & IRQ_FLG_SLOW) {
 296                 while (cur) {
 297                         list = &cur->next;
 298                         cur = cur->next;
 299                 }
 300         } else {
 301                 while (cur && !(cur->flags & IRQ_FLG_SLOW)) {
 302                         list = &cur->next;
 303                         cur = cur->next;
 304                 }
 305         }
 306
 307         node->next = cur;
 308         *list = node;
 309
 310         local_irq_restore(flags);
 311 }
 312
 313 static inline void mac_delete_irq(irq_node_t **list, void *dev_id)
 314 {
 315         unsigned long flags;
 316         irq_node_t *node;
 317
 318         local_irq_save(flags);
 319
 320         for (node = *list; node; list = &node->next, node = *list) {
 321                 if (node->dev_id == dev_id) {
 322                         *list = node->next;
 323                         /* Mark it as free. */
 324                         node->handler = NULL;
 325                         local_irq_restore(flags);
 326                         return;
 327                 }
 328         }
 329         local_irq_restore(flags);
 330         printk ("%s: tried to remove invalid irq\n", __FUNCTION__);
 331 }
 332
 333 /*
 334  * Call all the handlers for a given interrupt. Fast handlers are called
 335  * first followed by slow handlers.
 336  *
 337  * This code taken from the original Amiga code written by Roman Zippel.
 338  */
 339
 340 void mac_do_irq_list(int irq, struct pt_regs *fp)
 341 {
 342         irq_node_t *node, *slow_nodes;
 343         unsigned long flags;
 344
 345         kstat_cpu(0).irqs[irq]++;
 346
 347 #ifdef DEBUG_SPURIOUS
 348         if (!mac_irq_list[irq] && (console_loglevel > 7)) {
 349                 printk("mac_do_irq_list: spurious interrupt %d!\n", irq);
 350                 return;
 351         }
 352 #endif
 353
 354         /* serve first fast and normal handlers */
 355         for (node = mac_irq_list[irq];
 356              node && (!(node->flags & IRQ_FLG_SLOW));
 357              node = node->next)
 358                 node->handler(irq, node->dev_id, fp);
 359         if (!node) return;
 360         local_save_flags(flags);
 361         local_irq_restore((flags & ~0x0700) | (fp->sr & 0x0700));
 362         /* if slow handlers exists, serve them now */
 363         slow_nodes = node;
 364         for (; node; node = node->next) {
 365                 node->handler(irq, node->dev_id, fp);
 366         }
 367 }
 368
 369 /*
 370  *  mac_enable_irq - enable an interrupt source
 371  * mac_disable_irq - disable an interrupt source
 372  *   mac_clear_irq - clears a pending interrupt
 373  * mac_pending_irq - Returns the pending status of an IRQ (nonzero = pending)
 374  *
 375  * These routines are just dispatchers to the VIA/OSS/PSC routines.
 376  */
 377
 378 void mac_enable_irq (unsigned int irq)
 379 {
 380         int irq_src     = IRQ_SRC(irq);
 381
 382         switch(irq_src) {
 383                 case 1: via_irq_enable(irq);
 384                         break;
 385                 case 2:
 386                 case 7: if (oss_present) {
 387                                 oss_irq_enable(irq);
 388                         } else {
 389                                 via_irq_enable(irq);
 390                         }
 391                         break;
 392                 case 3:
 393                 case 4:
 394                 case 5:
 395                 case 6: if (psc_present) {
 396                                 psc_irq_enable(irq);
 397                         } else if (oss_present) {
 398                                 oss_irq_enable(irq);
 399                         } else if (irq_src == 4) {
 400                                 scc_irq_enable(irq);
 401                         }
 402                         break;
 403                 case 8: if (baboon_present) {
 404                                 baboon_irq_enable(irq);
 405                         }
 406                         break;
 407         }
 408 }
 409
 410 void mac_disable_irq (unsigned int irq)
 411 {
 412         int irq_src     = IRQ_SRC(irq);
 413
 414         switch(irq_src) {
 415                 case 1: via_irq_disable(irq);
 416                         break;
 417                 case 2:
 418                 case 7: if (oss_present) {
 419                                 oss_irq_disable(irq);
 420                         } else {
 421                                 via_irq_disable(irq);
 422                         }
 423                         break;
 424                 case 3:
 425                 case 4:
 426                 case 5:
 427                 case 6: if (psc_present) {
 428                                 psc_irq_disable(irq);
 429                         } else if (oss_present) {
 430                                 oss_irq_disable(irq);
 431                         } else if (irq_src == 4) {
 432                                 scc_irq_disable(irq);
 433                         }
 434                         break;
 435                 case 8: if (baboon_present) {
 436                                 baboon_irq_disable(irq);
 437                         }
 438                         break;
 439         }
 440 }
 441
 442 void mac_clear_irq( unsigned int irq )
 443 {
 444         switch(IRQ_SRC(irq)) {
 445                 case 1: via_irq_clear(irq);
 446                         break;
 447                 case 2:
 448                 case 7: if (oss_present) {
 449                                 oss_irq_clear(irq);
 450                         } else {
 451                                 via_irq_clear(irq);
 452                         }
 453                         break;
 454                 case 3:
 455                 case 4:
 456                 case 5:
 457                 case 6: if (psc_present) {
 458                                 psc_irq_clear(irq);
 459                         } else if (oss_present) {
 460                                 oss_irq_clear(irq);
 461                         }
 462                         break;
 463                 case 8: if (baboon_present) {
 464                                 baboon_irq_clear(irq);
 465                         }
 466                         break;
 467         }
 468 }
 469
 470 int mac_irq_pending( unsigned int irq )
 471 {
 472         switch(IRQ_SRC(irq)) {
 473                 case 1: return via_irq_pending(irq);
 474                 case 2:
 475                 case 7: if (oss_present) {
 476                                 return oss_irq_pending(irq);
 477                         } else {
 478                                 return via_irq_pending(irq);
 479                         }
 480                 case 3:
 481                 case 4:
 482                 case 5:
 483                 case 6: if (psc_present) {
 484                                 return psc_irq_pending(irq);
 485                         } else if (oss_present) {
 486                                 return oss_irq_pending(irq);
 487                         }
 488         }
 489         return 0;
 490 }
 491
 492 /*
 493  * Add an interrupt service routine to an interrupt source.
 494  * Returns 0 on success.
 495  *
 496  * FIXME: You can register interrupts on nonexistent source (ie PSC4 on a
 497  *        non-PSC machine). We should return -EINVAL in those cases.
 498  */
 499
 500 int mac_request_irq(unsigned int irq,
 501                     irqreturn_t (*handler)(int, void *, struct pt_regs *),
 502                     unsigned long flags, const char *devname, void *dev_id)
 503 {
 504         irq_node_t *node;
 505
 506 #ifdef DEBUG_MACINTS
 507         printk ("%s: irq %d requested for %s\n", __FUNCTION__, irq, devname);
 508 #endif
 509
 510         if (irq < VIA1_SOURCE_BASE) {
 511                 return cpu_request_irq(irq, handler, flags, devname, dev_id);
 512         }
 513
 514         if (irq >= NUM_MAC_SOURCES) {
 515                 printk ("%s: unknown irq %d requested by %s\n",
 516                         __FUNCTION__, irq, devname);
 517         }
 518
 519         /* Get a node and stick it onto the right list */
 520
 521         if (!(node = new_irq_node())) return -ENOMEM;
 522
 523         node->handler   = handler;
 524         node->flags     = flags;
 525         node->dev_id    = dev_id;
 526         node->devname   = devname;
 527         node->next      = NULL;
 528         mac_insert_irq(&mac_irq_list[irq], node);
 529
 530         /* Now enable the IRQ source */
 531
 532         mac_enable_irq(irq);
 533
 534         return 0;
 535 }
 536
 537 /*
 538  * Removes an interrupt service routine from an interrupt source.
 539  */
 540
 541 void mac_free_irq(unsigned int irq, void *dev_id)
 542 {
 543 #ifdef DEBUG_MACINTS
 544         printk ("%s: irq %d freed by %p\n", __FUNCTION__, irq, dev_id);
 545 #endif
 546
 547         if (irq < VIA1_SOURCE_BASE) {
 548                 cpu_free_irq(irq, dev_id);
 549                 return;
 550         }
 551
 552         if (irq >= NUM_MAC_SOURCES) {
 553                 printk ("%s: unknown irq %d freed\n",
 554                         __FUNCTION__, irq);
 555                 return;
 556         }
 557
 558         mac_delete_irq(&mac_irq_list[irq], dev_id);
 559
 560         /* If the list for this interrupt is */
 561         /* empty then disable the source.    */
 562
 563         if (!mac_irq_list[irq]) {
 564                 mac_disable_irq(irq);
 565         }
 566 }
 567
 568 /*
 569  * Generate a pretty listing for /proc/interrupts
 570  *
 571  * By the time we're called the autovector interrupt list has already been
 572  * generated, so we just need to do the machspec interrupts.
 573  *
 574  * 990506 (jmt) - rewritten to handle chained machspec interrupt handlers.
 575  *                Also removed display of num_spurious it is already
 576  *                displayed for us as autovector irq 0.
 577  */
 578
 579 int show_mac_interrupts(struct seq_file *p, void *v)
 580 {
 581         int i;
 582         irq_node_t *node;
 583         char *base;
 584
 585         /* Don't do Nubus interrupts in this loop; we do them separately  */
 586         /* below so that we can print slot numbers instead of IRQ numbers */
 587
 588         for (i = VIA1_SOURCE_BASE ; i < NUM_MAC_SOURCES ; ++i) {
 589
 590                 /* Nonexistant interrupt or nothing registered; skip it. */
 591
 592                 if ((node = mac_irq_list[i]) == NULL) continue;
 593                 if (node->flags & IRQ_FLG_STD) continue;
 594
 595                 base = "";
 596                 switch(IRQ_SRC(i)) {
 597                         case 1: base = "via1";
 598                                 break;
 599                         case 2: if (oss_present) {
 600                                         base = "oss";
 601                                 } else {
 602                                         base = "via2";
 603                                 }
 604                                 break;
 605                         case 3:
 606                         case 4:
 607                         case 5:
 608                         case 6: if (psc_present) {
 609                                         base = "psc";
 610                                 } else if (oss_present) {
 611                                         base = "oss";
 612                                 } else {
 613                                         if (IRQ_SRC(i) == 4) base = "scc";
 614                                 }
 615                                 break;
 616                         case 7: base = "nbus";
 617                                 break;
 618                         case 8: base = "bbn";
 619                                 break;
 620                 }
 621                 seq_printf(p, "%4s %2d: %10u ", base, i, kstat_cpu(0).irqs[i]);
 622
 623                 do {
 624                         if (node->flags & IRQ_FLG_FAST) {
 625                                 seq_puts(p, "F ");
 626                         } else if (node->flags & IRQ_FLG_SLOW) {
 627                                 seq_puts(p, "S ");
 628                         } else {
 629                                 seq_puts(p, "  ");
 630                         }
 631                         seq_printf(p, "%s\n", node->devname);
 632                         if ((node = node->next)) {
 633                                 seq_puts(p, "                    ");
 634                         }
 635                 } while(node);
 636
 637         }
 638         return 0;
 639 }
 640
 641 void mac_default_handler(int irq, void *dev_id, struct pt_regs *regs)
 642 {
 643 #ifdef DEBUG_SPURIOUS
 644         printk("Unexpected IRQ %d on device %p\n", irq, dev_id);
 645 #endif
 646 }
 647
 648 static int num_debug[8];
 649
 650 irqreturn_t mac_debug_handler(int irq, void *dev_id, struct pt_regs *regs)
 651 {
 652         if (num_debug[irq] < 10) {
 653                 printk("DEBUG: Unexpected IRQ %d\n", irq);
 654                 num_debug[irq]++;
 655         }
 656         return IRQ_HANDLED;
 657 }
 658
 659 static int in_nmi;
 660 static volatile int nmi_hold;
 661
 662 irqreturn_t mac_nmi_handler(int irq, void *dev_id, struct pt_regs *fp)
 663 {
 664         int i;
 665         /*
 666          * generate debug output on NMI switch if 'debug' kernel option given
 667          * (only works with Penguin!)
 668          */
 669
 670         in_nmi++;
 671         for (i=0; i<100; i++)
 672                 udelay(1000);
 673
 674         if (in_nmi == 1) {
 675                 nmi_hold = 1;
 676                 printk("... pausing, press NMI to resume ...");
 677         } else {
 678                 printk(" ok!\n");
 679                 nmi_hold = 0;
 680         }
 681
 682         barrier();
 683
 684         while (nmi_hold == 1)
 685                 udelay(1000);
 686
 687         if ( console_loglevel >= 8 ) {
 688 #if 0
 689                 show_state();
 690                 printk("PC: %08lx\nSR: %04x  SP: %p\n", fp->pc, fp->sr, fp);
 691                 printk("d0: %08lx    d1: %08lx    d2: %08lx    d3: %08lx\n",
 692                        fp->d0, fp->d1, fp->d2, fp->d3);
 693                 printk("d4: %08lx    d5: %08lx    a0: %08lx    a1: %08lx\n",
 694                        fp->d4, fp->d5, fp->a0, fp->a1);
 695
 696                 if (STACK_MAGIC != *(unsigned long *)current->kernel_stack_page)
 697                         printk("Corrupted stack page\n");
 698                 printk("Process %s (pid: %d, stackpage=%08lx)\n",
 699                         current->comm, current->pid, current->kernel_stack_page);
 700                 if (intr_count == 1)
 701                         dump_stack((struct frame *)fp);
 702 #else
 703                 /* printk("NMI "); */
 704 #endif
 705         }
 706         in_nmi--;
 707         return IRQ_HANDLED;
 708 }
 709
 710 /*
 711  * Simple routines for masking and unmasking
 712  * SCC interrupts in cases where this can't be
 713  * done in hardware (only the PSC can do that.)
 714  */
 715
 716 static void scc_irq_enable(int irq) {
 717         int irq_idx     = IRQ_IDX(irq);
 718
 719         scc_mask |= (1 << irq_idx);
 720 }
 721
 722 static void scc_irq_disable(int irq) {
 723         int irq_idx     = IRQ_IDX(irq);
 724
 725         scc_mask &= ~(1 << irq_idx);
 726 }
 727
 728 /*
 729  * SCC master interrupt handler. We have to do a bit of magic here
 730  * to figure out what channel gave us the interrupt; putting this
 731  * here is cleaner than hacking it into drivers/char/macserial.c.
 732  */
 733
 734 void mac_scc_dispatch(int irq, void *dev_id, struct pt_regs *regs)
 735 {
 736         volatile unsigned char *scc = (unsigned char *) mac_bi_data.sccbase + 2;
 737         unsigned char reg;
 738         unsigned long flags;
 739
 740         /* Read RR3 from the chip. Always do this on channel A */
 741         /* This must be an atomic operation so disable irqs.   */
 742
 743         local_irq_save(flags);
 744         *scc = 3;
 745         reg = *scc;
 746         local_irq_restore(flags);
 747
 748         /* Now dispatch. Bits 0-2 are for channel B and */
 749         /* bits 3-5 are for channel A. We can safely    */
 750         /* ignore the remaining bits here.              */
 751         /*                                              */
 752         /* Note that we're ignoring scc_mask for now.   */
 753         /* If we actually mask the ints then we tend to */
 754         /* get hammered by very persistent SCC irqs,    */
 755         /* and since they're autovector interrupts they */
 756         /* pretty much kill the system.                 */
 757
 758         if (reg & 0x38) mac_do_irq_list(IRQ_SCCA, regs);
 759         if (reg & 0x07) mac_do_irq_list(IRQ_SCCB, regs);
 760 }