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