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   1 /*
   2  * atari_dma_emul.c -- TT SCSI DMA emulator for the Hades.
   3  *
   4  * Copyright 1997 Wout Klaren <W.Klaren@inter.nl.net>
   5  *
   6  * This file is subject to the terms and conditions of the GNU General Public
   7  * License.  See the file COPYING in the main directory of this archive
   8  * for more details.
   9  *
  10  * This code was written using the Hades TOS source code as a
  11  * reference. This source code can be found on the home page
  12  * of Medusa Computer Systems.
  13  *
  14  * Version 0.1, 1997-09-24.
  15  *
  16  * This code should be considered experimental. It has only been
  17  * tested on a Hades with a 68060. It might not work on a Hades
  18  * with a 68040. Make backups of your hard drives before using
  19  * this code.
  20  */
  21
  22 #include <linux/compiler.h>
  23 #include <asm/thread_info.h>
  24 #include <asm/uaccess.h>
  25
  26 #define hades_dma_ctrl          (*(unsigned char *) 0xffff8717)
  27 #define hades_psdm_reg          (*(unsigned char *) 0xffff8741)
  28
  29 #define TRANSFER_SIZE           16
  30
  31 struct m68040_frame {
  32         unsigned long  effaddr;  /* effective address */
  33         unsigned short ssw;      /* special status word */
  34         unsigned short wb3s;     /* write back 3 status */
  35         unsigned short wb2s;     /* write back 2 status */
  36         unsigned short wb1s;     /* write back 1 status */
  37         unsigned long  faddr;    /* fault address */
  38         unsigned long  wb3a;     /* write back 3 address */
  39         unsigned long  wb3d;     /* write back 3 data */
  40         unsigned long  wb2a;     /* write back 2 address */
  41         unsigned long  wb2d;     /* write back 2 data */
  42         unsigned long  wb1a;     /* write back 1 address */
  43         unsigned long  wb1dpd0;  /* write back 1 data/push data 0*/
  44         unsigned long  pd1;      /* push data 1*/
  45         unsigned long  pd2;      /* push data 2*/
  46         unsigned long  pd3;      /* push data 3*/
  47 };
  48
  49 static void writeback (unsigned short wbs, unsigned long wba,
  50                        unsigned long wbd, void *old_buserr)
  51 {
  52         mm_segment_t fs = get_fs();
  53         static void *save_buserr;
  54
  55         __asm__ __volatile__ ("movec.l  %%vbr,%%a0\n\t"
  56                               "move.l   %0,8(%%a0)\n\t"
  57                               :
  58                               : "r" (&&bus_error)
  59                               : "a0" );
  60
  61         save_buserr = old_buserr;
  62
  63         set_fs (MAKE_MM_SEG(wbs & WBTM_040));
  64
  65         switch (wbs & WBSIZ_040) {
  66             case BA_SIZE_BYTE:
  67                 put_user (wbd & 0xff, (char *)wba);
  68                 break;
  69             case BA_SIZE_WORD:
  70                 put_user (wbd & 0xffff, (short *)wba);
  71                 break;
  72             case BA_SIZE_LONG:
  73                 put_user (wbd, (int *)wba);
  74                 break;
  75         }
  76
  77         set_fs (fs);
  78         return;
  79
  80 bus_error:
  81         __asm__ __volatile__ ("cmp.l    %0,2(%%sp)\n\t"
  82                               "bcs.s    .jump_old\n\t"
  83                               "cmp.l    %1,2(%%sp)\n\t"
  84                               "bls.s    .restore_old\n"
  85                         ".jump_old:\n\t"
  86                               "move.l   %2,-(%%sp)\n\t"
  87                               "rts\n"
  88                         ".restore_old:\n\t"
  89                               "move.l   %%a0,-(%%sp)\n\t"
  90                               "movec.l  %%vbr,%%a0\n\t"
  91                               "move.l   %2,8(%%a0)\n\t"
  92                               "move.l   (%%sp)+,%%a0\n\t"
  93                               "rte\n\t"
  94                               :
  95                               : "i" (writeback), "i" (&&bus_error),
  96                                 "m" (save_buserr) );
  97 }
  98
  99 /*
 100  * static inline void set_restdata_reg(unsigned char *cur_addr)
 101  *
 102  * Set the rest data register if necessary.
 103  */
 104
 105 static inline void set_restdata_reg(unsigned char *cur_addr)
 106 {
 107         if (((long) cur_addr & ~3) != 0)
 108                 tt_scsi_dma.dma_restdata =
 109                         *((unsigned long *) ((long) cur_addr & ~3));
 110 }
 111
 112 /*
 113  * void hades_dma_emulator(int irq, void *dummy, struct pt_regs *fp)
 114  *
 115  * This code emulates TT SCSI DMA on the Hades.
 116  *
 117  * Note the following:
 118  *
 119  * 1. When there is no byte available to read from the SCSI bus, or
 120  *    when a byte cannot yet bet written to the SCSI bus, a bus
 121  *    error occurs when reading or writing the pseudo DMA data
 122  *    register (hades_psdm_reg). We have to catch this bus error
 123  *    and try again to read or write the byte. If after several tries
 124  *    we still get a bus error, the interrupt handler is left. When
 125  *    the byte can be read or written, the interrupt handler is
 126  *    called again.
 127  *
 128  * 2. The SCSI interrupt must be disabled in this interrupt handler.
 129  *
 130  * 3. If we set the EOP signal, the SCSI controller still expects one
 131  *    byte to be read or written. Therefore the last byte is transferred
 132  *    separately, after setting the EOP signal.
 133  *
 134  * 4. When this function is left, the address pointer (start_addr) is
 135  *    converted to a physical address. Because it points one byte
 136  *    further than the last transferred byte, it can point outside the
 137  *    current page. If virt_to_phys() is called with this address we
 138  *    might get an access error. Therefore virt_to_phys() is called with
 139  *    start_addr - 1 if the count has reached zero. The result is
 140  *    increased with one.
 141  */
 142
 143 static irqreturn_t hades_dma_emulator(int irq, void *dummy, struct pt_regs *fp)
 144 {
 145         unsigned long dma_base;
 146         register unsigned long dma_cnt asm ("d3");
 147         static long save_buserr;
 148         register unsigned long save_sp asm ("d4");
 149         register int tries asm ("d5");
 150         register unsigned char *start_addr asm ("a3"), *end_addr asm ("a4");
 151         register unsigned char *eff_addr;
 152         register unsigned char *psdm_reg;
 153         unsigned long rem;
 154
 155         atari_disable_irq(IRQ_TT_MFP_SCSI);
 156
 157         /*
 158          * Read the dma address and count registers.
 159          */
 160
 161         dma_base = SCSI_DMA_READ_P(dma_addr);
 162         dma_cnt = SCSI_DMA_READ_P(dma_cnt);
 163
 164         /*
 165          * Check if DMA is still enabled.
 166          */
 167
 168         if ((tt_scsi_dma.dma_ctrl & 2) == 0)
 169         {
 170                 atari_enable_irq(IRQ_TT_MFP_SCSI);
 171                 return IRQ_HANDLED;
 172         }
 173
 174         if (dma_cnt == 0)
 175         {
 176                 printk(KERN_NOTICE "DMA emulation: count is zero.\n");
 177                 tt_scsi_dma.dma_ctrl &= 0xfd;   /* DMA ready. */
 178                 atari_enable_irq(IRQ_TT_MFP_SCSI);
 179                 return IRQ_HANDLED;
 180         }
 181
 182         /*
 183          * Install new bus error routine.
 184          */
 185
 186         __asm__ __volatile__ ("movec.l  %%vbr,%%a0\n\t"
 187                               "move.l   8(%%a0),%0\n\t"
 188                               "move.l   %1,8(%%a0)\n\t"
 189                               : "=&r" (save_buserr)
 190                               : "r" (&&scsi_bus_error)
 191                               : "a0" );
 192
 193         hades_dma_ctrl &= 0xfc;         /* Bus error and EOP off. */
 194
 195         /*
 196          * Save the stack pointer.
 197          */
 198
 199         __asm__ __volatile__ ("move.l   %%sp,%0\n\t"
 200                               : "=&r" (save_sp) );
 201
 202         tries = 100;                    /* Maximum number of bus errors. */
 203         start_addr = phys_to_virt(dma_base);
 204         end_addr = start_addr + dma_cnt;
 205
 206 scsi_loop:
 207         dma_cnt--;
 208         rem = dma_cnt & (TRANSFER_SIZE - 1);
 209         dma_cnt &= ~(TRANSFER_SIZE - 1);
 210         psdm_reg = &hades_psdm_reg;
 211
 212         if (tt_scsi_dma.dma_ctrl & 1)   /* Read or write? */
 213         {
 214                 /*
 215                  * SCSI write. Abort when count is zero.
 216                  */
 217
 218                 switch (rem)
 219                 {
 220                 case 0:
 221                         while (dma_cnt > 0)
 222                         {
 223                                 dma_cnt -= TRANSFER_SIZE;
 224
 225                                 *psdm_reg = *start_addr++;
 226                 case 15:
 227                                 *psdm_reg = *start_addr++;
 228                 case 14:
 229                                 *psdm_reg = *start_addr++;
 230                 case 13:
 231                                 *psdm_reg = *start_addr++;
 232                 case 12:
 233                                 *psdm_reg = *start_addr++;
 234                 case 11:
 235                                 *psdm_reg = *start_addr++;
 236                 case 10:
 237                                 *psdm_reg = *start_addr++;
 238                 case 9:
 239                                 *psdm_reg = *start_addr++;
 240                 case 8:
 241                                 *psdm_reg = *start_addr++;
 242                 case 7:
 243                                 *psdm_reg = *start_addr++;
 244                 case 6:
 245                                 *psdm_reg = *start_addr++;
 246                 case 5:
 247                                 *psdm_reg = *start_addr++;
 248                 case 4:
 249                                 *psdm_reg = *start_addr++;
 250                 case 3:
 251                                 *psdm_reg = *start_addr++;
 252                 case 2:
 253                                 *psdm_reg = *start_addr++;
 254                 case 1:
 255                                 *psdm_reg = *start_addr++;
 256                         }
 257                 }
 258
 259                 hades_dma_ctrl |= 1;    /* Set EOP. */
 260                 udelay(10);
 261                 *psdm_reg = *start_addr++;      /* Dummy byte. */
 262                 tt_scsi_dma.dma_ctrl &= 0xfd;   /* DMA ready. */
 263         }
 264         else
 265         {
 266                 /*
 267                  * SCSI read. Abort when count is zero.
 268                  */
 269
 270                 switch (rem)
 271                 {
 272                 case 0:
 273                         while (dma_cnt > 0)
 274                         {
 275                                 dma_cnt -= TRANSFER_SIZE;
 276
 277                                 *start_addr++ = *psdm_reg;
 278                 case 15:
 279                                 *start_addr++ = *psdm_reg;
 280                 case 14:
 281                                 *start_addr++ = *psdm_reg;
 282                 case 13:
 283                                 *start_addr++ = *psdm_reg;
 284                 case 12:
 285                                 *start_addr++ = *psdm_reg;
 286                 case 11:
 287                                 *start_addr++ = *psdm_reg;
 288                 case 10:
 289                                 *start_addr++ = *psdm_reg;
 290                 case 9:
 291                                 *start_addr++ = *psdm_reg;
 292                 case 8:
 293                                 *start_addr++ = *psdm_reg;
 294                 case 7:
 295                                 *start_addr++ = *psdm_reg;
 296                 case 6:
 297                                 *start_addr++ = *psdm_reg;
 298                 case 5:
 299                                 *start_addr++ = *psdm_reg;
 300                 case 4:
 301                                 *start_addr++ = *psdm_reg;
 302                 case 3:
 303                                 *start_addr++ = *psdm_reg;
 304                 case 2:
 305                                 *start_addr++ = *psdm_reg;
 306                 case 1:
 307                                 *start_addr++ = *psdm_reg;
 308                         }
 309                 }
 310
 311                 hades_dma_ctrl |= 1;    /* Set EOP. */
 312                 udelay(10);
 313                 *start_addr++ = *psdm_reg;
 314                 tt_scsi_dma.dma_ctrl &= 0xfd;   /* DMA ready. */
 315
 316                 set_restdata_reg(start_addr);
 317         }
 318
 319         if (start_addr != end_addr)
 320                 printk(KERN_CRIT "DMA emulation: FATAL: Count is not zero at end of transfer.\n");
 321
 322         dma_cnt = end_addr - start_addr;
 323
 324 scsi_end:
 325         dma_base = (dma_cnt == 0) ? virt_to_phys(start_addr - 1) + 1 :
 326                                     virt_to_phys(start_addr);
 327
 328         SCSI_DMA_WRITE_P(dma_addr, dma_base);
 329         SCSI_DMA_WRITE_P(dma_cnt, dma_cnt);
 330
 331         /*
 332          * Restore old bus error routine.
 333          */
 334
 335         __asm__ __volatile__ ("movec.l  %%vbr,%%a0\n\t"
 336                               "move.l   %0,8(%%a0)\n\t"
 337                               :
 338                               : "r" (save_buserr)
 339                               : "a0" );
 340
 341         atari_enable_irq(IRQ_TT_MFP_SCSI);
 342
 343         return IRQ_HANDLED;
 344
 345 scsi_bus_error:
 346         /*
 347          * First check if the bus error is caused by our code.
 348          * If not, call the original handler.
 349          */
 350
 351         __asm__ __volatile__ ("cmp.l    %0,2(%%sp)\n\t"
 352                               "bcs.s    .old_vector\n\t"
 353                               "cmp.l    %1,2(%%sp)\n\t"
 354                               "bls.s    .scsi_buserr\n"
 355                         ".old_vector:\n\t"
 356                               "move.l   %2,-(%%sp)\n\t"
 357                               "rts\n"
 358                         ".scsi_buserr:\n\t"
 359                               :
 360                               : "i" (&&scsi_loop), "i" (&&scsi_end),
 361                                 "m" (save_buserr) );
 362
 363         if (CPU_IS_060)
 364         {
 365                 /*
 366                  * Get effective address and restore the stack.
 367                  */
 368
 369                 __asm__ __volatile__ ("move.l   8(%%sp),%0\n\t"
 370                                       "move.l   %1,%%sp\n\t"
 371                                       : "=a&" (eff_addr)
 372                                       : "r" (save_sp) );
 373         }
 374         else
 375         {
 376                 register struct m68040_frame *frame;
 377
 378                 __asm__ __volatile__ ("lea      8(%%sp),%0\n\t"
 379                                       : "=a&" (frame) );
 380
 381                 if (tt_scsi_dma.dma_ctrl & 1)
 382                 {
 383                         /*
 384                          * Bus error while writing.
 385                          */
 386
 387                         if (frame->wb3s & WBV_040)
 388                         {
 389                                 if (frame->wb3a == (long) &hades_psdm_reg)
 390                                         start_addr--;
 391                                 else
 392                                         writeback(frame->wb3s, frame->wb3a,
 393                                                   frame->wb3d, &&scsi_bus_error);
 394                         }
 395
 396                         if (frame->wb2s & WBV_040)
 397                         {
 398                                 if (frame->wb2a == (long) &hades_psdm_reg)
 399                                         start_addr--;
 400                                 else
 401                                         writeback(frame->wb2s, frame->wb2a,
 402                                                   frame->wb2d, &&scsi_bus_error);
 403                         }
 404
 405                         if (frame->wb1s & WBV_040)
 406                         {
 407                                 if (frame->wb1a == (long) &hades_psdm_reg)
 408                                         start_addr--;
 409                         }
 410                 }
 411                 else
 412                 {
 413                         /*
 414                          * Bus error while reading.
 415                          */
 416
 417                         if (frame->wb3s & WBV_040)
 418                                 writeback(frame->wb3s, frame->wb3a,
 419                                           frame->wb3d, &&scsi_bus_error);
 420                 }
 421
 422                 eff_addr = (unsigned char *) frame->faddr;
 423
 424                 __asm__ __volatile__ ("move.l   %0,%%sp\n\t"
 425                                       :
 426                                       : "r" (save_sp) );
 427         }
 428
 429         dma_cnt = end_addr - start_addr;
 430
 431         if (eff_addr == &hades_psdm_reg)
 432         {
 433                 /*
 434                  * Bus error occurred while reading the pseudo
 435                  * DMA register. Time out.
 436                  */
 437
 438                 tries--;
 439
 440                 if (tries <= 0)
 441                 {
 442                         if ((tt_scsi_dma.dma_ctrl & 1) == 0)    /* Read or write? */
 443                                 set_restdata_reg(start_addr);
 444
 445                         if (dma_cnt <= 1)
 446                                 printk(KERN_CRIT "DMA emulation: Fatal "
 447                                        "error while %s the last byte.\n",
 448                                        (tt_scsi_dma.dma_ctrl & 1)
 449                                        ? "writing" : "reading");
 450
 451                         goto scsi_end;
 452                 }
 453                 else
 454                         goto scsi_loop;
 455         }
 456         else
 457         {
 458                 /*
 459                  * Bus error during pseudo DMA transfer.
 460                  * Terminate the DMA transfer.
 461                  */
 462
 463                 hades_dma_ctrl |= 3;    /* Set EOP and bus error. */
 464                 if ((tt_scsi_dma.dma_ctrl & 1) == 0)    /* Read or write? */
 465                         set_restdata_reg(start_addr);
 466                 goto scsi_end;
 467         }
 468 }