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
31struct 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
49static 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
80bus_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
105static 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)
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
143static irqreturn_t hades_dma_emulator(int irq, void *dummy)
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
206scsi_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
324scsi_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
345scsi_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}
469