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linux/drivers/scsi/atari_dma_emul.c

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/*
* atari_dma_emul.c -- TT SCSI DMA emulator for the Hades.
*
* Copyright 1997 Wout Klaren <W.Klaren@inter.nl.net>
*
* This file is subject to the terms and conditions of the GNU General Public
* License. See the file COPYING in the main directory of this archive
* for more details.
*
* This code was written using the Hades TOS source code as a
* reference. This source code can be found on the home page
* of Medusa Computer Systems.
*
* Version 0.1, 1997-09-24.
*
* This code should be considered experimental. It has only been
* tested on a Hades with a 68060. It might not work on a Hades
* with a 68040. Make backups of your hard drives before using
* this code.
*/
#include <linux/compiler.h>
#include <asm/thread_info.h>
#include <asm/uaccess.h>
#define hades_dma_ctrl (*(unsigned char *) 0xffff8717)
#define hades_psdm_reg (*(unsigned char *) 0xffff8741)
#define TRANSFER_SIZE 16
struct m68040_frame {
unsigned long effaddr; /* effective address */
unsigned short ssw; /* special status word */
unsigned short wb3s; /* write back 3 status */
unsigned short wb2s; /* write back 2 status */
unsigned short wb1s; /* write back 1 status */
unsigned long faddr; /* fault address */
unsigned long wb3a; /* write back 3 address */
unsigned long wb3d; /* write back 3 data */
unsigned long wb2a; /* write back 2 address */
unsigned long wb2d; /* write back 2 data */
unsigned long wb1a; /* write back 1 address */
unsigned long wb1dpd0; /* write back 1 data/push data 0*/
unsigned long pd1; /* push data 1*/
unsigned long pd2; /* push data 2*/
unsigned long pd3; /* push data 3*/
};
static void writeback (unsigned short wbs, unsigned long wba,
unsigned long wbd, void *old_buserr)
{
mm_segment_t fs = get_fs();
static void *save_buserr;
__asm__ __volatile__ ("movec.l %%vbr,%%a0\n\t"
"move.l %0,8(%%a0)\n\t"
:
: "r" (&&bus_error)
: "a0" );
save_buserr = old_buserr;
set_fs (MAKE_MM_SEG(wbs & WBTM_040));
switch (wbs & WBSIZ_040) {
case BA_SIZE_BYTE:
put_user (wbd & 0xff, (char *)wba);
break;
case BA_SIZE_WORD:
put_user (wbd & 0xffff, (short *)wba);
break;
case BA_SIZE_LONG:
put_user (wbd, (int *)wba);
break;
}
set_fs (fs);
return;
bus_error:
__asm__ __volatile__ ("cmp.l %0,2(%%sp)\n\t"
"bcs.s .jump_old\n\t"
"cmp.l %1,2(%%sp)\n\t"
"bls.s .restore_old\n"
".jump_old:\n\t"
"move.l %2,-(%%sp)\n\t"
"rts\n"
".restore_old:\n\t"
"move.l %%a0,-(%%sp)\n\t"
"movec.l %%vbr,%%a0\n\t"
"move.l %2,8(%%a0)\n\t"
"move.l (%%sp)+,%%a0\n\t"
"rte\n\t"
:
: "i" (writeback), "i" (&&bus_error),
"m" (save_buserr) );
}
/*
* static inline void set_restdata_reg(unsigned char *cur_addr)
*
* Set the rest data register if necessary.
*/
static inline void set_restdata_reg(unsigned char *cur_addr)
{
if (((long) cur_addr & ~3) != 0)
tt_scsi_dma.dma_restdata =
*((unsigned long *) ((long) cur_addr & ~3));
}
/*
* void hades_dma_emulator(int irq, void *dummy)
*
* This code emulates TT SCSI DMA on the Hades.
*
* Note the following:
*
* 1. When there is no byte available to read from the SCSI bus, or
* when a byte cannot yet bet written to the SCSI bus, a bus
* error occurs when reading or writing the pseudo DMA data
* register (hades_psdm_reg). We have to catch this bus error
* and try again to read or write the byte. If after several tries
* we still get a bus error, the interrupt handler is left. When
* the byte can be read or written, the interrupt handler is
* called again.
*
* 2. The SCSI interrupt must be disabled in this interrupt handler.
*
* 3. If we set the EOP signal, the SCSI controller still expects one
* byte to be read or written. Therefore the last byte is transferred
* separately, after setting the EOP signal.
*
* 4. When this function is left, the address pointer (start_addr) is
* converted to a physical address. Because it points one byte
* further than the last transferred byte, it can point outside the
* current page. If virt_to_phys() is called with this address we
* might get an access error. Therefore virt_to_phys() is called with
* start_addr - 1 if the count has reached zero. The result is
* increased with one.
*/
static irqreturn_t hades_dma_emulator(int irq, void *dummy)
{
unsigned long dma_base;
register unsigned long dma_cnt asm ("d3");
static long save_buserr;
register unsigned long save_sp asm ("d4");
register int tries asm ("d5");
register unsigned char *start_addr asm ("a3"), *end_addr asm ("a4");
register unsigned char *eff_addr;
register unsigned char *psdm_reg;
unsigned long rem;
atari_disable_irq(IRQ_TT_MFP_SCSI);
/*
* Read the dma address and count registers.
*/
dma_base = SCSI_DMA_READ_P(dma_addr);
dma_cnt = SCSI_DMA_READ_P(dma_cnt);
/*
* Check if DMA is still enabled.
*/
if ((tt_scsi_dma.dma_ctrl & 2) == 0)
{
atari_enable_irq(IRQ_TT_MFP_SCSI);
return IRQ_HANDLED;
}
if (dma_cnt == 0)
{
printk(KERN_NOTICE "DMA emulation: count is zero.\n");
tt_scsi_dma.dma_ctrl &= 0xfd; /* DMA ready. */
atari_enable_irq(IRQ_TT_MFP_SCSI);
return IRQ_HANDLED;
}
/*
* Install new bus error routine.
*/
__asm__ __volatile__ ("movec.l %%vbr,%%a0\n\t"
"move.l 8(%%a0),%0\n\t"
"move.l %1,8(%%a0)\n\t"
: "=&r" (save_buserr)
: "r" (&&scsi_bus_error)
: "a0" );
hades_dma_ctrl &= 0xfc; /* Bus error and EOP off. */
/*
* Save the stack pointer.
*/
__asm__ __volatile__ ("move.l %%sp,%0\n\t"
: "=&r" (save_sp) );
tries = 100; /* Maximum number of bus errors. */
start_addr = phys_to_virt(dma_base);
end_addr = start_addr + dma_cnt;
scsi_loop:
dma_cnt--;
rem = dma_cnt & (TRANSFER_SIZE - 1);
dma_cnt &= ~(TRANSFER_SIZE - 1);
psdm_reg = &hades_psdm_reg;
if (tt_scsi_dma.dma_ctrl & 1) /* Read or write? */
{
/*
* SCSI write. Abort when count is zero.
*/
switch (rem)
{
case 0:
while (dma_cnt > 0)
{
dma_cnt -= TRANSFER_SIZE;
*psdm_reg = *start_addr++;
case 15:
*psdm_reg = *start_addr++;
case 14:
*psdm_reg = *start_addr++;
case 13:
*psdm_reg = *start_addr++;
case 12:
*psdm_reg = *start_addr++;
case 11:
*psdm_reg = *start_addr++;
case 10:
*psdm_reg = *start_addr++;
case 9:
*psdm_reg = *start_addr++;
case 8:
*psdm_reg = *start_addr++;
case 7:
*psdm_reg = *start_addr++;
case 6:
*psdm_reg = *start_addr++;
case 5:
*psdm_reg = *start_addr++;
case 4:
*psdm_reg = *start_addr++;
case 3:
*psdm_reg = *start_addr++;
case 2:
*psdm_reg = *start_addr++;
case 1:
*psdm_reg = *start_addr++;
}
}
hades_dma_ctrl |= 1; /* Set EOP. */
udelay(10);
*psdm_reg = *start_addr++; /* Dummy byte. */
tt_scsi_dma.dma_ctrl &= 0xfd; /* DMA ready. */
}
else
{
/*
* SCSI read. Abort when count is zero.
*/
switch (rem)
{
case 0:
while (dma_cnt > 0)
{
dma_cnt -= TRANSFER_SIZE;
*start_addr++ = *psdm_reg;
case 15:
*start_addr++ = *psdm_reg;
case 14:
*start_addr++ = *psdm_reg;
case 13:
*start_addr++ = *psdm_reg;
case 12:
*start_addr++ = *psdm_reg;
case 11:
*start_addr++ = *psdm_reg;
case 10:
*start_addr++ = *psdm_reg;
case 9:
*start_addr++ = *psdm_reg;
case 8:
*start_addr++ = *psdm_reg;
case 7:
*start_addr++ = *psdm_reg;
case 6:
*start_addr++ = *psdm_reg;
case 5:
*start_addr++ = *psdm_reg;
case 4:
*start_addr++ = *psdm_reg;
case 3:
*start_addr++ = *psdm_reg;
case 2:
*start_addr++ = *psdm_reg;
case 1:
*start_addr++ = *psdm_reg;
}
}
hades_dma_ctrl |= 1; /* Set EOP. */
udelay(10);
*start_addr++ = *psdm_reg;
tt_scsi_dma.dma_ctrl &= 0xfd; /* DMA ready. */
set_restdata_reg(start_addr);
}
if (start_addr != end_addr)
printk(KERN_CRIT "DMA emulation: FATAL: Count is not zero at end of transfer.\n");
dma_cnt = end_addr - start_addr;
scsi_end:
dma_base = (dma_cnt == 0) ? virt_to_phys(start_addr - 1) + 1 :
virt_to_phys(start_addr);
SCSI_DMA_WRITE_P(dma_addr, dma_base);
SCSI_DMA_WRITE_P(dma_cnt, dma_cnt);
/*
* Restore old bus error routine.
*/
__asm__ __volatile__ ("movec.l %%vbr,%%a0\n\t"
"move.l %0,8(%%a0)\n\t"
:
: "r" (save_buserr)
: "a0" );
atari_enable_irq(IRQ_TT_MFP_SCSI);
return IRQ_HANDLED;
scsi_bus_error:
/*
* First check if the bus error is caused by our code.
* If not, call the original handler.
*/
__asm__ __volatile__ ("cmp.l %0,2(%%sp)\n\t"
"bcs.s .old_vector\n\t"
"cmp.l %1,2(%%sp)\n\t"
"bls.s .scsi_buserr\n"
".old_vector:\n\t"
"move.l %2,-(%%sp)\n\t"
"rts\n"
".scsi_buserr:\n\t"
:
: "i" (&&scsi_loop), "i" (&&scsi_end),
"m" (save_buserr) );
if (CPU_IS_060)
{
/*
* Get effective address and restore the stack.
*/
__asm__ __volatile__ ("move.l 8(%%sp),%0\n\t"
"move.l %1,%%sp\n\t"
: "=a&" (eff_addr)
: "r" (save_sp) );
}
else
{
register struct m68040_frame *frame;
__asm__ __volatile__ ("lea 8(%%sp),%0\n\t"
: "=a&" (frame) );
if (tt_scsi_dma.dma_ctrl & 1)
{
/*
* Bus error while writing.
*/
if (frame->wb3s & WBV_040)
{
if (frame->wb3a == (long) &hades_psdm_reg)
start_addr--;
else
writeback(frame->wb3s, frame->wb3a,
frame->wb3d, &&scsi_bus_error);
}
if (frame->wb2s & WBV_040)
{
if (frame->wb2a == (long) &hades_psdm_reg)
start_addr--;
else
writeback(frame->wb2s, frame->wb2a,
frame->wb2d, &&scsi_bus_error);
}
if (frame->wb1s & WBV_040)
{
if (frame->wb1a == (long) &hades_psdm_reg)
start_addr--;
}
}
else
{
/*
* Bus error while reading.
*/
if (frame->wb3s & WBV_040)
writeback(frame->wb3s, frame->wb3a,
frame->wb3d, &&scsi_bus_error);
}
eff_addr = (unsigned char *) frame->faddr;
__asm__ __volatile__ ("move.l %0,%%sp\n\t"
:
: "r" (save_sp) );
}
dma_cnt = end_addr - start_addr;
if (eff_addr == &hades_psdm_reg)
{
/*
* Bus error occurred while reading the pseudo
* DMA register. Time out.
*/
tries--;
if (tries <= 0)
{
if ((tt_scsi_dma.dma_ctrl & 1) == 0) /* Read or write? */
set_restdata_reg(start_addr);
if (dma_cnt <= 1)
printk(KERN_CRIT "DMA emulation: Fatal "
"error while %s the last byte.\n",
(tt_scsi_dma.dma_ctrl & 1)
? "writing" : "reading");
goto scsi_end;
}
else
goto scsi_loop;
}
else
{
/*
* Bus error during pseudo DMA transfer.
* Terminate the DMA transfer.
*/
hades_dma_ctrl |= 3; /* Set EOP and bus error. */
if ((tt_scsi_dma.dma_ctrl & 1) == 0) /* Read or write? */
set_restdata_reg(start_addr);
goto scsi_end;
}
}
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