cpu/nios/traps.S

   1 /*
   2  * (C) Copyright 2003, Psyent Corporation <www.psyent.com>
   3  * Scott McNutt <smcnutt@psyent.com>
   4  *
   5  * See file CREDITS for list of people who contributed to this
   6  * project.
   7  *
   8  * This program is free software; you can redistribute it and/or
   9  * modify it under the terms of the GNU General Public License as
  10  * published by the Free Software Foundation; either version 2 of
  11  * the License, or (at your option) any later version.
  12  *
  13  * This program is distributed in the hope that it will be useful,
  14  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  15  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  16  * GNU General Public License for more details.
  17  *
  18  * You should have received a copy of the GNU General Public License
  19  * along with this program; if not, write to the Free Software
  20  * Foundation, Inc., 59 Temple Place, Suite 330, Boston,
  21  * MA 02111-1307 USA
  22  */
  23
  24 #include <config.h>
  25
  26 /*************************************************************************
  27  * Register window underflow
  28  *
  29  * The register window underflow exception occurs whenever the lowest
  30  * valid register window is in use (CWP=LO_LIMIT) and a save instruction
  31  * is issued. The save moves CWP below LO_LIMIT, %sp is set as normal,
  32  * then the exception is generated prior to executing the instruction
  33  * after the save.
  34  ************************************************************************/
  35         .text
  36         .global _cwp_lolimit
  37         .align  4
  38
  39 _cwp_lolimit:
  40
  41         /* Sixteen words are always allocated by the compiler in every
  42          * procedure's stack frame, always starting at %sp, for saving
  43          * 'in' and 'local' registers on a window overflow.
  44          *
  45          * Save the 'global' and 'in' regs on stack. They are restored
  46          * at cwp = HI_LIMIT. The 'local' regs aren't in-use at this point.
  47          */
  48         sts     [%sp,0], %g0            /* Save 'global' regs*/
  49         sts     [%sp,1], %g1
  50         sts     [%sp,2], %g2
  51         sts     [%sp,3], %g3
  52         sts     [%sp,4], %g4
  53         sts     [%sp,5], %g5
  54         sts     [%sp,6], %g6
  55         sts     [%sp,7], %g7
  56
  57         sts     [%sp,8], %i0            /* Save 'in' regs */
  58         sts     [%sp,9], %i1
  59         sts     [%sp,10], %i2
  60         sts     [%sp,11], %i3
  61         sts     [%sp,12], %i4
  62         sts     [%sp,13], %i5
  63         sts     [%sp,14], %i6
  64         sts     [%sp,15], %i7
  65
  66         /* Save current %sp and return address in a global so they are
  67          * available at cwp = HI_LIMIT ... where the 'global'/'in' regs
  68          * are restored. NOTE: %sp changes with cwp.
  69          */
  70         mov     %g7, %o7
  71         mov     %g6, %sp
  72
  73         /* Get LO_LIMIT/HI_LIMIT to know where to start & stop. Note: in
  74          * the underflow exception, cwp is __NOT__ guaranteed to be zero.
  75          * If the OCI debug module is enabled the reset value for LO_LIMIT
  76          * is 2, not 1 -- so cwp can be 1 or 0.
  77          */
  78         pfx     2                       /* WVALID */
  79         rdctl   %g1
  80         mov     %g2, %g1
  81         pfx     0
  82         and     %g1, 0x1f               /* g1 <- LO_LIMIT */
  83         lsri    %g2, 5
  84         pfx     0
  85         and     %g2,0x1f                /* g2 <- HI_LIMIT */
  86
  87         /* Set istatus so cwp = HI_LIMIT after tret
  88          */
  89         movi    %g5, 0x1f
  90         lsli    %g5, 4
  91         not     %g5                     /* mask to clr cwp */
  92         pfx     1                       /* istatus */
  93         rdctl   %g0
  94         and     %g0, %g5                /* clear cwp field */
  95
  96         mov     %g4, %g2
  97         lsli    %g4, 4
  98         or      %g0, %g4                /* cwp = HI_LIMIT */
  99         pfx     1
 100         wrctl   %g0                     /* update istatus */
 101
 102         /* Now move up the register file, saving as we go. When loop
 103          * is first entered, %g1 is at LO_LIMIT.
 104          */
 105 0:
 106         restore                         /* cwp++ */
 107         sts     [%sp,0], %l0            /* Save "local" regs*/
 108         sts     [%sp,1], %l1
 109         sts     [%sp,2], %l2
 110         sts     [%sp,3], %l3
 111         sts     [%sp,4], %l4
 112         sts     [%sp,5], %l5
 113         sts     [%sp,6], %l6
 114         sts     [%sp,7], %l7
 115
 116         sts     [%sp,8], %i0            /* Save 'in' regs */
 117         sts     [%sp,9], %i1
 118         sts     [%sp,10], %i2
 119         sts     [%sp,11], %i3
 120         sts     [%sp,12], %i4
 121         sts     [%sp,13], %i5
 122         sts     [%sp,14], %i6
 123         sts     [%sp,15], %i7
 124
 125         cmp     %g1, %g2                /* cwp == HI_LIMIT ? */
 126         skps    cc_ne                   /* if so, we're done */
 127         br      1f
 128         nop                             /* delay slot */
 129
 130         inc     %g1                     /* g1 <- cwp++ */
 131         br      0b
 132         nop                             /* delay slot */
 133
 134         /* At this point cwp = HI_LIMIT, so the global/in regs that were
 135          * in place when the underflow occurred must be restored using
 136          * the original stack pointer (saved in g6).
 137          */
 138 1:
 139         mov     %o7, %g7                /* restore return addr */
 140         mov     %sp, %g6                /* Restore original sp */
 141
 142         lds     %g0, [%sp,0]            /* Restore 'global' regs*/
 143         lds     %g1, [%sp,1]
 144         lds     %g2, [%sp,2]
 145         lds     %g3, [%sp,3]
 146         lds     %g4, [%sp,4]
 147         lds     %g5, [%sp,5]
 148         lds     %g6, [%sp,6]
 149         lds     %g7, [%sp,7]
 150
 151         lds     %i0, [%sp,8]            /* Restore 'in' regs*/
 152         lds     %i1, [%sp,9]
 153         lds     %i2, [%sp,10]
 154         lds     %i3, [%sp,11]
 155         lds     %i4, [%sp,12]
 156         lds     %i5, [%sp,13]
 157         lds     %i6, [%sp,14]
 158         lds     %i7, [%sp,15]
 159
 160         tret    %o7                     /* All done */
 161
 162 /*************************************************************************
 163  * Register window overflow
 164  *
 165  * The register window overflow exception occurs whenever the highest
 166  * valid register window is in use (cwp = HI_LIMIT) and a restore
 167  * instruction is issued. Control is transferred to the overflow handler
 168  * before the instruction following restore is executed.
 169  *
 170  * When a register window overflow exception is taken, the exception
 171  * handler sees cwp at HI_LIMIT.
 172  ************************************************************************/
 173         .text
 174         .global _cwp_hilimit
 175         .align  4
 176
 177 _cwp_hilimit:
 178
 179         /* Save 'global'/'in' regs on the stack -- will restore when cwp
 180          * is at LO_LIMIT. Locals don't need saving as they are going away.
 181          */
 182         sts     [%sp,0], %g0            /* Save "global" regs*/
 183         sts     [%sp,1], %g1
 184         sts     [%sp,2], %g2
 185         sts     [%sp,3], %g3
 186         sts     [%sp,4], %g4
 187         sts     [%sp,5], %g5
 188         sts     [%sp,6], %g6
 189         sts     [%sp,7], %g7
 190
 191         sts     [%sp,8], %i0            /* Save 'in' regs */
 192         sts     [%sp,9], %i1
 193         sts     [%sp,10], %i2
 194         sts     [%sp,11], %i3
 195         sts     [%sp,12], %i4
 196         sts     [%sp,13], %i5
 197         sts     [%sp,14], %i6
 198         sts     [%sp,15], %i7
 199
 200         /* The current %sp must be available in global to restore regs
 201          * saved on stack. Need return addr as well ;-)
 202          */
 203         mov     %g7, %o7
 204         mov     %g6, %sp
 205
 206         /* Get HI_LIMIT & LO_LIMIT
 207          */
 208         pfx     2                       /* WVALID */
 209         rdctl   %g1
 210         mov     %g2, %g1
 211         pfx     0
 212         and     %g1, 0x1f               /* g1 <- LO_LIMIT */
 213         lsri    %g2, 5
 214         pfx     0
 215         and     %g2,0x1f                /* g2 <- HI_LIMIT */
 216
 217         /* Set istatus so cwp = LO_LIMIT after tret
 218          */
 219         movi    %g5, 0x1f
 220         lsli    %g5, 4
 221         not     %g5                     /* mask to clr cwp */
 222         pfx     1                       /* istatus */
 223         rdctl   %g0
 224         and     %g0, %g5                /* clear cwp field */
 225
 226         mov     %g4, %g1                /* g4 <- LO_LIMIT */
 227         lsli    %g4, 4
 228         or      %g0, %g4                /* cwp = LO_LIMIT */
 229         pfx     1
 230         wrctl   %g0                     /* update istatus */
 231
 232         /* Move to cwp = LO_LIMIT-1 and restore 'in' regs.
 233          */
 234         subi    %g4,(1 << 4)            /* g4 <- LO_LIMIT - 1 */
 235         rdctl   %g0
 236         and     %g0, %g5                /* clear cwp field */
 237         or      %g0, %g4                /* cwp = LO_LIMIT - 1 */
 238         wrctl   %g0                     /* update status */
 239         nop
 240
 241         mov     %sp, %g6                /* Restore sp */
 242         lds     %i0, [%sp,8]            /* Restore 'in' regs */
 243         lds     %i1, [%sp,9]
 244         lds     %i2, [%sp,10]
 245         lds     %i3, [%sp,11]
 246         lds     %i4, [%sp,12]
 247         lds     %i5, [%sp,13]
 248         lds     %i6, [%sp,14]           /* sp in next window */
 249         lds     %i7, [%sp,15]
 250
 251         /* Starting at LO_LIMIT-1, move up the register file, restoring
 252          * along the way.
 253          */
 254 0:
 255         restore                         /* cwp++ */
 256         lds     %l0, [%sp,0]            /* Restore 'local' regs*/
 257         lds     %l1, [%sp,1]
 258         lds     %l2, [%sp,2]
 259         lds     %l3, [%sp,3]
 260         lds     %l4, [%sp,4]
 261         lds     %l5, [%sp,5]
 262         lds     %l6, [%sp,6]
 263         lds     %l7, [%sp,7]
 264
 265         lds     %i0, [%sp,8]            /* Restore 'in' regs */
 266         lds     %i1, [%sp,9]
 267         lds     %i2, [%sp,10]
 268         lds     %i3, [%sp,11]
 269         lds     %i4, [%sp,12]
 270         lds     %i5, [%sp,13]
 271         lds     %i6, [%sp,14]           /* sp in next window */
 272         lds     %i7, [%sp,15]
 273
 274         cmp     %g1, %g2                /* cwp == HI_LIMIT ? */
 275         skps    cc_ne                   /* if so, we're done */
 276         br      1f
 277         nop                             /* delay slot */
 278
 279         inc     %g1                     /* cwp++ */
 280         br      0b
 281         nop                             /* delay slot */
 282
 283         /* All windows have been updated at this point, but the globals
 284          * still need to be restored. Go to cwp = LO_LIMIT-1 to get
 285          * some registers to use.
 286          */
 287 1:
 288         rdctl   %g0
 289         and     %g0, %g5                /* clear cwp field */
 290         or      %g0, %g4                /* cwp = LO_LIMIT - 1 */
 291         wrctl   %g0                     /* update status */
 292         nop
 293
 294         /* Now there are some registers available to use in restoring
 295          * the globals.
 296          */
 297         mov     %sp, %g6
 298         mov     %o7, %g7
 299
 300         lds     %g0, [%sp,0]            /* Restore "global" regs*/
 301         lds     %g1, [%sp,1]
 302         lds     %g2, [%sp,2]
 303         lds     %g3, [%sp,3]
 304         lds     %g4, [%sp,4]
 305         lds     %g5, [%sp,5]
 306         lds     %g6, [%sp,6]
 307         lds     %g7, [%sp,7]
 308
 309         /* The tret moves istatus -> status. istatus was already set for
 310          * cwp = LO_LIMIT.
 311          */
 312
 313         tret    %o7                     /* done */
 314
 315 /*************************************************************************
 316  * Default exception handler
 317  *
 318  * The default handler passes control to external_interrupt(). So trap
 319  * or hardware interrupt hanlders can be installed using the familiar
 320  * irq_install_handler().
 321  *
 322  * Here, the stack is fixed-up and cwp is incremented prior to calling
 323  * external_interrupt(). This lets the underflow and overflow handlers
 324  * operate normally during the exception.
 325  ************************************************************************/
 326         .text
 327         .global _def_xhandler
 328         .align  4
 329
 330 _def_xhandler:
 331
 332         /* Allocate some stack space: 16 words at %sp to accomodate
 333          * a reg window underflow, 8 words to save interrupted task's
 334          * 'out' regs (which are now the 'in' regs), 8 words to preserve
 335          * the 'global' regs and 3 words to save the return address,
 336          * status and istatus. istatus must be saved in the event an
 337          * underflow occurs in a dispatched handler. status is saved so
 338          * a handler can access it on stack.
 339          */
 340         pfx     %hi((16+16+3) * 4)
 341         subi    %fp, %lo((16+16+3) * 4)
 342         mov     %sp, %fp
 343
 344         /* Save the 'global' regs and the interrupted task's 'out' regs
 345          * (our 'in' regs) along with the return addr, status & istatus.
 346          * First 16 words are for underflow exception.
 347          */
 348         rdctl   %l0                     /* status */
 349         pfx     1                       /* istatus */
 350         rdctl   %l1
 351
 352         sts     [%sp,16+0], %g0         /* Save 'global' regs*/
 353         sts     [%sp,16+1], %g1
 354         sts     [%sp,16+2], %g2
 355         sts     [%sp,16+3], %g3
 356         sts     [%sp,16+4], %g4
 357         sts     [%sp,16+5], %g5
 358         sts     [%sp,16+6], %g6
 359         sts     [%sp,16+7], %g7
 360
 361         sts     [%sp,16+8], %i0         /* Save 'in' regs */
 362         sts     [%sp,16+9], %i1
 363         sts     [%sp,16+10], %i2
 364         sts     [%sp,16+11], %i3
 365         sts     [%sp,16+12], %i4
 366         sts     [%sp,16+13], %i5
 367         sts     [%sp,16+14], %i6
 368         sts     [%sp,16+15], %i7
 369
 370         sts     [%sp,16+16], %l0        /* status */
 371         sts     [%sp,16+17], %l1        /* istatus */
 372         sts     [%sp,16+18], %o7        /* return addr */
 373
 374         /* Move to cwp+1 ... this guarantees cwp is at or above LO_LIMIT.
 375          * Need to set IPRI=3 and IE=1 to enable underflow exceptions.
 376          * NOTE: only the 'out' regs have been saved ... can't touch
 377          * the 'in' or 'local' here.
 378          */
 379         restore                         /* cwp++ */
 380         rdctl   %o0                     /* o0 <- status */
 381
 382         pfx     %hi(0x7e00)
 383         movi    %o1, %lo(0x7e00)
 384         not     %o1
 385         and     %o0, %o1                /* clear IPRI */
 386
 387         pfx     %hi(0x8600)
 388         movi    %o1, %lo(0x8600)
 389         or      %o0, %o1                /* IPRI=3, IE=1 */
 390
 391         wrctl   %o0                     /* o0 -> status */
 392         nop
 393
 394         /* It's ok to call a C routine now since cwp >= LO_LIMIT,
 395          * interrupt task's registers are/will be preserved, and
 396          * underflow exceptions can be handled.
 397          */
 398         pfx     %hi(external_interrupt@h)
 399         movi    %o1, %lo(external_interrupt@h)
 400         pfx     %xhi(external_interrupt@h)
 401         movhi   %o1, %xlo(external_interrupt@h)
 402         bgen    %o0, 4+2                /* 16 * 4 */
 403         add     %o0, %sp                /* Ptr to regs */
 404         call    %o1
 405         nop
 406
 407         /* Move back to the exception register window, restore the 'out'
 408          * registers, then return from exception.
 409          */
 410         rdctl   %o0                     /* o0 <- status */
 411         subi    %o0, 16
 412         wrctl   %o0                     /* cwp-- */
 413         nop
 414
 415         mov     %sp, %fp
 416         lds     %g0, [%sp,16+0]         /* Restore 'global' regs*/
 417         lds     %g1, [%sp,16+1]
 418         lds     %g2, [%sp,16+2]
 419         lds     %g3, [%sp,16+3]
 420         lds     %g4, [%sp,16+4]
 421         lds     %g5, [%sp,16+5]
 422         lds     %g6, [%sp,16+6]
 423         lds     %g7, [%sp,16+7]
 424
 425         lds     %i0, [%sp,16+8]         /* Restore 'in' regs*/
 426         lds     %i1, [%sp,16+9]
 427         lds     %i2, [%sp,16+10]
 428         lds     %i3, [%sp,16+11]
 429         lds     %i4, [%sp,16+12]
 430         lds     %i5, [%sp,16+13]
 431         lds     %i6, [%sp,16+14]
 432         lds     %i7, [%sp,16+15]
 433
 434         lds     %l0, [%sp,16+16]        /* status */
 435         lds     %l1, [%sp,16+17]        /* istatus */
 436         lds     %o7, [%sp,16+18]        /* return addr */
 437
 438         pfx     1
 439         wrctl   %l1                     /* restore istatus */
 440
 441         pfx     %hi((16+16+3) * 4)
 442         addi    %sp, %lo((16+16+3) * 4)
 443         mov     %fp, %sp
 444
 445         tret    %o7                     /* Done */
 446
 447
 448 /*************************************************************************
 449  * Timebase Timer Interrupt -- This has identical structure to above,
 450  * but calls timer_interrupt().  Doing it this way keeps things similar
 451  * to other architectures (e.g. ppc).
 452  ************************************************************************/
 453         .text
 454         .global _timebase_int
 455         .align  4
 456
 457 _timebase_int:
 458
 459         /* Allocate  stack space.
 460          */
 461         pfx     %hi((16+16+3) * 4)
 462         subi    %fp, %lo((16+16+3) * 4)
 463         mov     %sp, %fp
 464
 465         /* Save the 'global' regs & 'out' regs (our 'in' regs)
 466          */
 467         rdctl   %l0                     /* status */
 468         pfx     1                       /* istatus */
 469         rdctl   %l1
 470
 471         sts     [%sp,16+0], %g0         /* Save 'global' regs*/
 472         sts     [%sp,16+1], %g1
 473         sts     [%sp,16+2], %g2
 474         sts     [%sp,16+3], %g3
 475         sts     [%sp,16+4], %g4
 476         sts     [%sp,16+5], %g5
 477         sts     [%sp,16+6], %g6
 478         sts     [%sp,16+7], %g7
 479
 480         sts     [%sp,16+8], %i0         /* Save 'in' regs */
 481         sts     [%sp,16+9], %i1
 482         sts     [%sp,16+10], %i2
 483         sts     [%sp,16+11], %i3
 484         sts     [%sp,16+12], %i4
 485         sts     [%sp,16+13], %i5
 486         sts     [%sp,16+14], %i6
 487         sts     [%sp,16+15], %i7
 488
 489         sts     [%sp,16+16], %l0        /* status */
 490         sts     [%sp,16+17], %l1        /* istatus */
 491         sts     [%sp,16+18], %o7        /* return addr */
 492
 493         /* Move to cwp+1.
 494          */
 495         restore                         /* cwp++ */
 496         rdctl   %o0                     /* o0 <- status */
 497
 498         pfx     %hi(0x7e00)
 499         movi    %o1, %lo(0x7e00)
 500         not     %o1
 501         and     %o0, %o1                /* clear IPRI */
 502
 503         pfx     %hi(0x8600)
 504         movi    %o1, %lo(0x8600)
 505         or      %o0, %o1                /* IPRI=3, IE=1 */
 506
 507         wrctl   %o0                     /* o0 -> status */
 508         nop
 509
 510         /* Call timer_interrupt()
 511          */
 512         pfx     %hi(timer_interrupt@h)
 513         movi    %o1, %lo(timer_interrupt@h)
 514         pfx     %xhi(timer_interrupt@h)
 515         movhi   %o1, %xlo(timer_interrupt@h)
 516         bgen    %o0, 4+2                /* 16 * 4 */
 517         add     %o0, %sp                /* Ptr to regs */
 518         call    %o1
 519         nop
 520
 521         /* Move back to the exception register window, restore the 'out'
 522          * registers, then return from exception.
 523          */
 524         rdctl   %o0                     /* o0 <- status */
 525         subi    %o0, 16
 526         wrctl   %o0                     /* cwp-- */
 527         nop
 528
 529         mov     %sp, %fp
 530         lds     %g0, [%sp,16+0]         /* Restore 'global' regs*/
 531         lds     %g1, [%sp,16+1]
 532         lds     %g2, [%sp,16+2]
 533         lds     %g3, [%sp,16+3]
 534         lds     %g4, [%sp,16+4]
 535         lds     %g5, [%sp,16+5]
 536         lds     %g6, [%sp,16+6]
 537         lds     %g7, [%sp,16+7]
 538
 539         lds     %i0, [%sp,16+8]         /* Restore 'in' regs*/
 540         lds     %i1, [%sp,16+9]
 541         lds     %i2, [%sp,16+10]
 542         lds     %i3, [%sp,16+11]
 543         lds     %i4, [%sp,16+12]
 544         lds     %i5, [%sp,16+13]
 545         lds     %i6, [%sp,16+14]
 546         lds     %i7, [%sp,16+15]
 547
 548         lds     %l0, [%sp,16+16]        /* status */
 549         lds     %l1, [%sp,16+17]        /* istatus */
 550         lds     %o7, [%sp,16+18]        /* return addr */
 551
 552         pfx     1
 553         wrctl   %l1                     /* restore istatus */
 554
 555         pfx     %hi((16+16+3) * 4)
 556         addi    %sp, %lo((16+16+3) * 4)
 557         mov     %fp, %sp
 558
 559         tret    %o7                     /* Done */