path: root/arch/cris/drivers/ide.c

/* $Id: ide.c,v 1.4 2001/01/10 21:14:32 bjornw Exp $
 *
 * Etrax specific IDE functions, like init and PIO-mode setting etc.
 * Almost the entire ide.c is used for the rest of the Etrax ATA driver.
 * Copyright (c) 2000, 2001 Axis Communications AB 
 *
 * Authors:    Bjorn Wesen        (initial version)
 *             Mikael Starvik     (pio setup stuff)
 *
 * $Log: ide.c,v $
 * Revision 1.4  2001/01/10 21:14:32  bjornw
 * Initialize hwif->ideproc, for the new way of handling ide_xxx_data
 *
 * Revision 1.3  2000/12/01 17:48:18  bjornw
 * - atapi_output_bytes now uses DMA
 * - dma_active check removed - the kernel does proper serializing and it had
 *   a race-condition anyway
 * - ide_build_dmatable had a nameclash
 * - re-added the RESET_DMA thingys because sometimes the interface can get
 *   stuck apparently
 * - added ide_release_dma
 *
 * Revision 1.2  2000/11/29 17:31:29  bjornw
 * 2.4 port
 *
 * - The "register addresses" stored in the hwif are now 32-bit fields that
 *   don't need to be shifted into correct positions in R_ATA_CTRL_DATA
 * - PIO-mode detection temporarily disabled since ide-modes.c is not compiled
 * - All DMA uses virt_to_phys conversions for DMA buffers and descriptor ptrs
 * - Probably correct ide_dma_begin semantics in dmaproc now for ATAPI devices
 * - Removed RESET_DMA when starting a new transfer - why was this necessary ?
 * - Indentation fix
 *
 *
 */

/* Regarding DMA: 
 *
 * There are two forms of DMA - "DMA handshaking" between the interface and the drive,
 * and DMA between the memory and the interface. We can ALWAYS use the latter, since it's
 * something built-in in the Etrax. However only some drives support the DMA-mode handshaking
 * on the ATA-bus. The normal PC driver and Triton interface disables memory-if DMA when the
 * device can't do DMA handshaking for some stupid reason. We don't need to do that.
 */ 

#undef REALLY_SLOW_IO           /* most systems can safely undef this */

#include <linux/config.h>
#include <linux/types.h>
#include <linux/kernel.h>
#include <linux/timer.h>
#include <linux/mm.h>
#include <linux/interrupt.h>
#include <linux/delay.h>
#include <linux/blkdev.h>
#include <linux/hdreg.h>
#include <linux/ide.h>
#include <linux/init.h>

#include <asm/io.h>
#include <asm/svinto.h>

/* number of Etrax DMA descriptors */
#define MAX_DMA_DESCRS 64

#define LOWDB(x)
#define D(x)

void OUT_BYTE(unsigned char data, ide_ioreg_t reg) {
	LOWDB(printk("ob: data 0x%x, reg 0x%x\n", data, reg));
	while(*R_ATA_STATUS_DATA & IO_MASK(R_ATA_STATUS_DATA, busy)); /* wait for busy flag */
	*R_ATA_CTRL_DATA = reg | data; /* write data to the drive's register */
	while(!(*R_ATA_STATUS_DATA &
		IO_MASK(R_ATA_STATUS_DATA, tr_rdy))); /* wait for transmitter ready */
}

unsigned char IN_BYTE(ide_ioreg_t reg) {
	int status;
	while(*R_ATA_STATUS_DATA & IO_MASK(R_ATA_STATUS_DATA, busy)); /* wait for busy flag */
	*R_ATA_CTRL_DATA = reg | IO_STATE(R_ATA_CTRL_DATA, rw, read); /* read data */ 
	while(!((status = *R_ATA_STATUS_DATA) &
		IO_MASK(R_ATA_STATUS_DATA, dav))); /* wait for available */
	LOWDB(printk("inb: 0x%x from reg 0x%x\n", status & 0xff, reg));
	return (unsigned char)status; /* data was in the lower 16 bits in the status reg */
}

/* PIO timing (in R_ATA_CONFIG)
 *
 *                        _____________________________
 * ADDRESS :     ________/
 *
 *                            _______________
 * DIOR    :     ____________/               \__________
 *
 *                               _______________
 * DATA    :     XXXXXXXXXXXXXXXX_______________XXXXXXXX
 *
 *
 * DIOR is unbuffered while address and data is buffered.
 * This creates two problems:
 * 1. The DIOR pulse is to early (because it is unbuffered)
 * 2. The rise time of DIOR is long
 *
 * There are at least three different plausible solutions
 * 1. Use a pad capable of larger currents in Etrax
 * 2. Use an external buffer
 * 3. Make the strobe pulse longer
 *
 * Some of the strobe timings below are modified to compensate
 * for this. This implies a slight performance decrease.
 *
 * THIS SHOULD NEVER BE CHANGED!
 *
 * TODO: Is this true for the latest LX boards still ?
 */

#define ATA_DMA2_STROBE  4 
#define ATA_DMA2_HOLD    0
#define ATA_DMA1_STROBE  4 
#define ATA_DMA1_HOLD    1
#define ATA_DMA0_STROBE 12 
#define ATA_DMA0_HOLD    9
#define ATA_PIO4_SETUP   1
#define ATA_PIO4_STROBE  5
#define ATA_PIO4_HOLD    0
#define ATA_PIO3_SETUP   1
#define ATA_PIO3_STROBE  5
#define ATA_PIO3_HOLD    1
#define ATA_PIO2_SETUP   1
#define ATA_PIO2_STROBE  6
#define ATA_PIO2_HOLD    2
#define ATA_PIO1_SETUP   2
#define ATA_PIO1_STROBE 11
#define ATA_PIO1_HOLD    4
#define ATA_PIO0_SETUP   4
#define ATA_PIO0_STROBE 19
#define ATA_PIO0_HOLD    4

/*
 * good_dma_drives() lists the model names (from "hdparm -i")
 * of drives which do not support mword2 DMA but which are
 * known to work fine with this interface under Linux.
 */

const char *good_dma_drives[] = {"Micropolis 2112A",
				 "CONNER CTMA 4000",
				 "CONNER CTT8000-A",
				 NULL};

static void tune_e100_ide(ide_drive_t *drive, byte pio)
{
	unsigned long flags;
	
	pio = 4;
	//pio = ide_get_best_pio_mode(drive, pio, 4, NULL);
	
	save_flags(flags);
	cli();

	/* set pio mode! */
  	 
	switch(pio) {
		case 0:
			*R_ATA_CONFIG = ( IO_FIELD( R_ATA_CONFIG, enable,     1 ) |
					  IO_FIELD( R_ATA_CONFIG, dma_strobe, ATA_DMA2_STROBE ) |
					  IO_FIELD( R_ATA_CONFIG, dma_hold,   ATA_DMA2_HOLD ) |
					  IO_FIELD( R_ATA_CONFIG, pio_setup,  ATA_PIO0_SETUP ) |
					  IO_FIELD( R_ATA_CONFIG, pio_strobe, ATA_PIO0_STROBE ) |
					  IO_FIELD( R_ATA_CONFIG, pio_hold,   ATA_PIO0_HOLD ) );
			break;
		case 1:
			*R_ATA_CONFIG = ( IO_FIELD( R_ATA_CONFIG, enable,     1 ) |
					  IO_FIELD( R_ATA_CONFIG, dma_strobe, ATA_DMA2_STROBE ) |
					  IO_FIELD( R_ATA_CONFIG, dma_hold,   ATA_DMA2_HOLD ) |
					  IO_FIELD( R_ATA_CONFIG, pio_setup,  ATA_PIO1_SETUP ) |
					  IO_FIELD( R_ATA_CONFIG, pio_strobe, ATA_PIO1_STROBE ) |
					  IO_FIELD( R_ATA_CONFIG, pio_hold,   ATA_PIO1_HOLD ) );
			break;
		case 2:
			*R_ATA_CONFIG = ( IO_FIELD( R_ATA_CONFIG, enable,     1 ) |
					  IO_FIELD( R_ATA_CONFIG, dma_strobe, ATA_DMA2_STROBE ) |
					  IO_FIELD( R_ATA_CONFIG, dma_hold,   ATA_DMA2_HOLD ) |
					  IO_FIELD( R_ATA_CONFIG, pio_setup,  ATA_PIO2_SETUP ) |
					  IO_FIELD( R_ATA_CONFIG, pio_strobe, ATA_PIO2_STROBE ) |
					  IO_FIELD( R_ATA_CONFIG, pio_hold,   ATA_PIO2_HOLD ) );
			break;
		case 3:
			*R_ATA_CONFIG = ( IO_FIELD( R_ATA_CONFIG, enable,     1 ) |
					  IO_FIELD( R_ATA_CONFIG, dma_strobe, ATA_DMA2_STROBE ) |
					  IO_FIELD( R_ATA_CONFIG, dma_hold,   ATA_DMA2_HOLD ) |
					  IO_FIELD( R_ATA_CONFIG, pio_setup,  ATA_PIO3_SETUP ) |
					  IO_FIELD( R_ATA_CONFIG, pio_strobe, ATA_PIO3_STROBE ) |
					  IO_FIELD( R_ATA_CONFIG, pio_hold,   ATA_PIO3_HOLD ) );
			break;
		case 4:
			*R_ATA_CONFIG = ( IO_FIELD( R_ATA_CONFIG, enable,     1 ) |
					  IO_FIELD( R_ATA_CONFIG, dma_strobe, ATA_DMA2_STROBE ) |
					  IO_FIELD( R_ATA_CONFIG, dma_hold,   ATA_DMA2_HOLD ) |
					  IO_FIELD( R_ATA_CONFIG, pio_setup,  ATA_PIO4_SETUP ) |
					  IO_FIELD( R_ATA_CONFIG, pio_strobe, ATA_PIO4_STROBE ) |
					  IO_FIELD( R_ATA_CONFIG, pio_hold,   ATA_PIO4_HOLD ) );
			break;
	}
	restore_flags(flags);
}

static int e100_dmaproc (ide_dma_action_t func, ide_drive_t *drive); /* defined below */
static void e100_ideproc (ide_ide_action_t func, ide_drive_t *drive,
			  void *buffer, unsigned int length);        /* defined below */

void __init init_e100_ide (void)
{
	volatile unsigned int dummy;
	int h;

	printk("ide: ETRAX 100LX built-in ATA DMA controller\n");

	/* first fill in some stuff in the ide_hwifs fields */
	
	for(h = 0; h < MAX_HWIFS; h++) {
		ide_hwif_t *hwif = &ide_hwifs[h];
		hwif->chipset = ide_etrax100;
		hwif->tuneproc = &tune_e100_ide;
		hwif->dmaproc = &e100_dmaproc;
		hwif->ideproc = &e100_ideproc;
	}
	/* actually reset and configure the etrax100 ide/ata interface */

	/* de-assert bus-reset */
#ifdef CONFIG_ETRAX_IDE_PB7_RESET  
	port_pb_dir_shadow = port_pb_dir_shadow | 
		IO_STATE(R_PORT_PB_DIR, dir7, output);
	*R_PORT_PB_DIR = port_pb_dir_shadow;
	REG_SHADOW_SET(R_PORT_PB_DATA, port_pb_data_shadow, 7, 1);
#endif
#ifdef CONFIG_ETRAX_IDE_G27_RESET
	*R_PORT_G_DATA = 0;
#endif 

	*R_ATA_CTRL_DATA = 0;
	*R_ATA_TRANSFER_CNT = 0;
	*R_ATA_CONFIG = 0;

	genconfig_shadow = (genconfig_shadow & 
			    ~IO_MASK(R_GEN_CONFIG, dma2) &
			    ~IO_MASK(R_GEN_CONFIG, dma3) &
			    ~IO_MASK(R_GEN_CONFIG, ata)) | 
		( IO_STATE( R_GEN_CONFIG, dma3, ata    ) |
		  IO_STATE( R_GEN_CONFIG, dma2, ata    ) |
		  IO_STATE( R_GEN_CONFIG, ata,  select ) );

	*R_GEN_CONFIG = genconfig_shadow;

#ifdef CONFIG_ETRAX_IDE_CSE1_16_RESET
	*(volatile long *)(MEM_CSE1_START | MEM_NON_CACHEABLE) = 0;
#endif

	/* wait some */

	dummy = 1;
	dummy = 2;
	dummy = 3;

#ifdef CONFIG_ETRAX_IDE_CSE1_16_RESET
	*(volatile long *)(MEM_CSE1_START | MEM_NON_CACHEABLE) = 1 << 16;
	*R_PORT_G_DATA = 0;  /* de-assert bus-reset */
#endif

	/* make a dummy read to set the ata controller in a proper state */
	dummy = *R_ATA_STATUS_DATA;
  
	*R_ATA_CONFIG = ( IO_FIELD( R_ATA_CONFIG, enable,     1 ) |
			  IO_FIELD( R_ATA_CONFIG, dma_strobe, ATA_DMA2_STROBE ) |
			  IO_FIELD( R_ATA_CONFIG, dma_hold,   ATA_DMA2_HOLD ) |
			  IO_FIELD( R_ATA_CONFIG, pio_setup,  ATA_PIO4_SETUP ) |
			  IO_FIELD( R_ATA_CONFIG, pio_strobe, ATA_PIO4_STROBE ) |
			  IO_FIELD( R_ATA_CONFIG, pio_hold,   ATA_PIO4_HOLD ) );

	*R_ATA_CTRL_DATA = ( IO_STATE( R_ATA_CTRL_DATA, rw,   read) |
			     IO_FIELD( R_ATA_CTRL_DATA, addr, 1   ) );

	while(*R_ATA_STATUS_DATA & IO_MASK(R_ATA_STATUS_DATA, busy)); /* wait for busy flag*/

	*R_IRQ_MASK0_SET = ( IO_STATE( R_IRQ_MASK0_SET, ata_irq0, set ) |
			     IO_STATE( R_IRQ_MASK0_SET, ata_irq1, set ) |
			     IO_STATE( R_IRQ_MASK0_SET, ata_irq2, set ) |
			     IO_STATE( R_IRQ_MASK0_SET, ata_irq3, set ) );

	printk("ide: waiting 10 seconds for drives to regain consciousness\n");

	h = jiffies + 1000;
	while(jiffies < h) ;

  /* reset the dma channels we will use */

	RESET_DMA(2);
	RESET_DMA(3);
	WAIT_DMA(2);
	WAIT_DMA(3);

}

static etrax_dma_descr mydescr;

/*
 * The following routines are mainly used by the ATAPI drivers.
 *
 * These routines will round up any request for an odd number of bytes,
 * so if an odd bytecount is specified, be sure that there's at least one
 * extra byte allocated for the buffer.
 */
static void 
e100_atapi_input_bytes (ide_drive_t *drive, void *buffer, unsigned int bytecount)
{
	ide_ioreg_t data_reg = IDE_DATA_REG;
	unsigned long status;

	D(printk("atapi_input_bytes, dreg 0x%x, buffer 0x%x, count %d\n",
		 data_reg, buffer, bytecount));
	
	if(bytecount & 1) {
		printk("warning, odd bytecount in cdrom_in_bytes = %d.\n", bytecount);
		bytecount++; /* to round off */
	}
	
	/* make sure the DMA channel is available */
	RESET_DMA(3);
	WAIT_DMA(3); 
	
	/* setup DMA descriptor */
	
	mydescr.sw_len = bytecount;
	mydescr.ctrl   = d_eol;
	mydescr.buf    = virt_to_phys(buffer);
	
	/* start the dma channel */
	
	*R_DMA_CH3_FIRST = virt_to_phys(&mydescr);
	*R_DMA_CH3_CMD   = IO_STATE(R_DMA_CH3_CMD, cmd, start);
	
	/* initiate a multi word dma read using PIO handshaking */
	
	*R_ATA_TRANSFER_CNT = bytecount >> 1;
	
	*R_ATA_CTRL_DATA = data_reg |
		IO_STATE(R_ATA_CTRL_DATA, rw,       read) |
		IO_STATE(R_ATA_CTRL_DATA, src_dst,  dma) |
		IO_STATE(R_ATA_CTRL_DATA, handsh,   pio) |
		IO_STATE(R_ATA_CTRL_DATA, multi,    on) |
		IO_STATE(R_ATA_CTRL_DATA, dma_size, word);
	
	/* wait for completion */
	
	LED_DISK_READ(1);
	WAIT_DMA(3);
	LED_DISK_READ(0);
	
#if 0
	/* old polled transfer code */
	
	/* initiate a multi word read */
	
	*R_ATA_TRANSFER_CNT = wcount << 1;
	
	*R_ATA_CTRL_DATA = data_reg |
		IO_STATE(R_ATA_CTRL_DATA, rw,       read) |
		IO_STATE(R_ATA_CTRL_DATA, src_dst,  register) |
		IO_STATE(R_ATA_CTRL_DATA, handsh,   pio) |
		IO_STATE(R_ATA_CTRL_DATA, multi,    on) |
		IO_STATE(R_ATA_CTRL_DATA, dma_size, word);
	
	/* svinto has a latency until the busy bit actually is set */
	
	nop(); nop();
	nop(); nop();
	nop(); nop();
	nop(); nop();
	nop(); nop();
	
	/* unit should be busy during multi transfer */
	while((status = *R_ATA_STATUS_DATA) & IO_MASK(R_ATA_STATUS_DATA, busy)) {
		while(!(status & IO_MASK(R_ATA_STATUS_DATA, dav)))
			status = *R_ATA_STATUS_DATA;
		*ptr++ = (unsigned short)(status & 0xffff);
	}
#endif
}

static void 
e100_atapi_output_bytes (ide_drive_t *drive, void *buffer, unsigned int bytecount)
{
	ide_ioreg_t data_reg = IDE_DATA_REG;
	unsigned short *ptr = (unsigned short *)buffer;
	unsigned long ctrl;
	
	D(printk("atapi_output_bytes, dreg 0x%x, buffer 0x%x, count %d\n",
		 data_reg, buffer, bytecount));

	if(bytecount & 1) {
		printk("odd bytecount %d in atapi_out_bytes!\n", bytecount);
		bytecount++;
	}

	/* make sure the DMA channel is available */
	RESET_DMA(2);
	WAIT_DMA(2); 
	
	/* setup DMA descriptor */
	
	mydescr.sw_len = bytecount;
	mydescr.ctrl   = d_eol;
	mydescr.buf    = virt_to_phys(buffer);

	/* start the dma channel */
	
	*R_DMA_CH2_FIRST = virt_to_phys(&mydescr);
	*R_DMA_CH2_CMD   = IO_STATE(R_DMA_CH2_CMD, cmd, start);
	
	/* initiate a multi word dma write using PIO handshaking */
	
	*R_ATA_TRANSFER_CNT = bytecount >> 1;
	
	*R_ATA_CTRL_DATA = data_reg |
		IO_STATE(R_ATA_CTRL_DATA, rw,       write) |
		IO_STATE(R_ATA_CTRL_DATA, src_dst,  dma) |
		IO_STATE(R_ATA_CTRL_DATA, handsh,   pio) |
		IO_STATE(R_ATA_CTRL_DATA, multi,    on) |
		IO_STATE(R_ATA_CTRL_DATA, dma_size, word);
	
	/* wait for completion */
	
	LED_DISK_WRITE(1);
	WAIT_DMA(2);
	LED_DISK_WRITE(0);

#if 0
	/* old polled write code */

	while(*R_ATA_STATUS_DATA & IO_MASK(R_ATA_STATUS_DATA, busy)); /* wait for busy flag */

	/* initiate a multi word write */

	*R_ATA_TRANSFER_CNT = bytecount >> 1;

	ctrl = data_reg |
		IO_STATE(R_ATA_CTRL_DATA, rw,       write) |
		IO_STATE(R_ATA_CTRL_DATA, src_dst,  register) |
		IO_STATE(R_ATA_CTRL_DATA, handsh,   pio) |
		IO_STATE(R_ATA_CTRL_DATA, multi,    on) |
		IO_STATE(R_ATA_CTRL_DATA, dma_size, word);
	
	LED_DISK_WRITE(1);
	
	/* Etrax will set busy = 1 until the multi pio transfer has finished
	 * and tr_rdy = 1 after each succesful word transfer. 
	 * When the last byte has been transferred Etrax will first set tr_tdy = 1 
	 * and then busy = 0 (not in the same cycle). If we read busy before it
	 * has been set to 0 we will think that we should transfer more bytes 
	 * and then tr_rdy would be 0 forever. This is solved by checking busy
	 * in the inner loop.
	 */
	
	do {
		*R_ATA_CTRL_DATA = ctrl | *ptr++;
		while(!(*R_ATA_STATUS_DATA & IO_MASK(R_ATA_STATUS_DATA, tr_rdy)) &&
		      (*R_ATA_STATUS_DATA & IO_MASK(R_ATA_STATUS_DATA, busy)));
	} while(*R_ATA_STATUS_DATA & IO_MASK(R_ATA_STATUS_DATA, busy));

	LED_DISK_WRITE(0);
#endif	
}

/*
 * This is used for most PIO data transfers *from* the IDE interface
 */
static void 
e100_ide_input_data (ide_drive_t *drive, void *buffer, unsigned int wcount)
{
	e100_atapi_input_bytes(drive, buffer, wcount << 2);
}

/*
 * This is used for most PIO data transfers *to* the IDE interface
 */
static void
e100_ide_output_data (ide_drive_t *drive, void *buffer, unsigned int wcount)
{
	e100_atapi_output_bytes(drive, buffer, wcount << 2);
}

/*
 * The multiplexor for ide_xxxput_data and atapi calls
 */
static void 
e100_ideproc (ide_ide_action_t func, ide_drive_t *drive,
	      void *buffer, unsigned int length)
{
	switch (func) {
		case ideproc_ide_input_data:
			e100_ide_input_data(drive, buffer, length);
			break;
		case ideproc_ide_output_data:
			e100_ide_input_data(drive, buffer, length);
			break;
		case ideproc_atapi_input_bytes:
			e100_atapi_input_bytes(drive, buffer, length);
			break;
		case ideproc_atapi_output_bytes:
			e100_atapi_output_bytes(drive, buffer, length);
			break;
		default:
			printk("e100_ideproc: unsupported func %d!\n", func);
			break;
	}
}

/* we only have one DMA channel on the chip for ATA, so we can keep these statically */
static etrax_dma_descr ata_descrs[MAX_DMA_DESCRS];
static unsigned int ata_tot_size;

/*
 * e100_ide_build_dmatable() prepares a dma request.
 * Returns 0 if all went okay, returns 1 otherwise.
 */
static int e100_ide_build_dmatable (ide_drive_t *drive)
{
	struct request *rq = HWGROUP(drive)->rq;
	struct buffer_head *bh = rq->bh;
	unsigned long size, addr;
	unsigned int count = 0;

	ata_tot_size = 0;

	do {
		/*
		 * Determine addr and size of next buffer area.  We assume that
		 * individual virtual buffers are always composed linearly in
		 * physical memory.  For example, we assume that any 8kB buffer
		 * is always composed of two adjacent physical 4kB pages rather
		 * than two possibly non-adjacent physical 4kB pages.
		 */
		if (bh == NULL) {  /* paging and tape requests have (rq->bh == NULL) */
			addr = virt_to_phys (rq->buffer);
			size = rq->nr_sectors << 9;
		} else {
			/* group sequential buffers into one large buffer */
			addr = virt_to_phys (bh->b_data);
			size = bh->b_size;
			while ((bh = bh->b_reqnext) != NULL) {
				if ((addr + size) != virt_to_phys (bh->b_data))
					break;
				size += bh->b_size;
			}
		}

		/* did we run out of descriptors? */

		if(count >= MAX_DMA_DESCRS) {
			printk("%s: too few DMA descriptors\n", drive->name);
			return 1;
		}

		/* uh.. I'm lazy.. if size >= 65536, it should loop below and split it in
		   more than one descriptor */

		if(size >= 65536) {
			printk("too large ATA DMA request block, size = %d!\n", size);
			return 1;
		}

		/* however, this case is more difficult - R_ATA_TRANSFER_CNT cannot be more
		   than 65536 words per transfer, so in that case we need to either 
		   1) use a DMA interrupt to re-trigger R_ATA_TRANSFER_CNT and continue with
		      the descriptors, or
		   2) simply do the request here, and get dma_intr to only ide_end_request on 
		      those blocks that were actually set-up for transfer.
		*/

		if(ata_tot_size + size >= 131072) {
			printk("too large total ATA DMA request, %d + %d!\n", ata_tot_size, size);
			return 1;
		}

		/* ok we want to do IO at addr, size bytes. set up a new descriptor entry */

		ata_descrs[count].sw_len = size;
		ata_descrs[count].ctrl = 0;
		ata_descrs[count].buf = addr;
		ata_descrs[count].next = virt_to_phys(&ata_descrs[count + 1]);
		count++;
		ata_tot_size += size;

	} while (bh != NULL);

	if (count) {
		/* set the end-of-list flag on the last descriptor */
		ata_descrs[count - 1].ctrl |= d_eol;
		/* return and say all is ok */
		return 0;
	}

	printk("%s: empty DMA table?\n", drive->name);
	return 1;	/* let the PIO routines handle this weirdness */
}

static int config_drive_for_dma (ide_drive_t *drive)
{
        const char **list;
        struct hd_driveid *id = drive->id;

        if (id && (id->capability & 1)) {
                /* Enable DMA on any drive that supports mword2 DMA */
                if ((id->field_valid & 2) && (id->dma_mword & 0x404) == 0x404) {
                        drive->using_dma = 1;
                        return 0;               /* DMA enabled */
                }

                /* Consult the list of known "good" drives */
                list = good_dma_drives;
                while (*list) {
                        if (!strcmp(*list++,id->model)) {
                                drive->using_dma = 1;
                                return 0;       /* DMA enabled */
                        }
                }
        }
        return 1;       /* DMA not enabled */
}

/*
 * etrax_dma_intr() is the handler for disk read/write DMA interrupts
 */
static ide_startstop_t etrax_dma_intr (ide_drive_t *drive)
{
	int i, dma_stat;
	byte stat;

	LED_DISK_READ(0);
	LED_DISK_WRITE(0);

	dma_stat = HWIF(drive)->dmaproc(ide_dma_end, drive);
	stat = GET_STAT();			/* get drive status */
	if (OK_STAT(stat,DRIVE_READY,drive->bad_wstat|DRQ_STAT)) {
		if (!dma_stat) {
			struct request *rq;
			rq = HWGROUP(drive)->rq;
			for (i = rq->nr_sectors; i > 0;) {
				i -= rq->current_nr_sectors;
				ide_end_request(1, HWGROUP(drive));
			}
			return ide_stopped;
		}
		printk("%s: bad DMA status\n", drive->name);
	}
	return ide_error(drive, "dma_intr", stat);
}

/*
 * e100_dmaproc() initiates/aborts DMA read/write operations on a drive.
 *
 * The caller is assumed to have selected the drive and programmed the drive's
 * sector address using CHS or LBA.  All that remains is to prepare for DMA
 * and then issue the actual read/write DMA/PIO command to the drive.
 *
 * For ATAPI devices, we just prepare for DMA and return. The caller should
 * then issue the packet command to the drive and call us again with
 * ide_dma_begin afterwards.
 *
 * Returns 0 if all went well.
 * Returns 1 if DMA read/write could not be started, in which case
 * the caller should revert to PIO for the current request.
 */

static int e100_dmaproc (ide_dma_action_t func, ide_drive_t *drive)
{
        static unsigned int reading; /* static to support ide_dma_begin semantics */
	int atapi = 0;

	D(printk("e100_dmaproc func %d\n", func));

        switch (func) {
		case ide_dma_verbose:
			return 0;
                case ide_dma_check:
                        return config_drive_for_dma (drive);
		case ide_dma_off:
		case ide_dma_off_quietly:
			/* ok.. we don't really need to do anything I think. */
			return 0;
                case ide_dma_write:
                        reading = 0;
			break;
                case ide_dma_read:
			reading = 1;
                        break;
                case ide_dma_begin:
			/* begin DMA, used by ATAPI devices which want to issue the 
			 * appropriate IDE command themselves.
			 *
			 * they have already called ide_dma_read/write to set the
			 * static reading flag, now they call ide_dma_begin to do
			 * the real stuff. we tell our code below not to issue
			 * any IDE commands itself and jump into it. 
			 */
			atapi++;
			goto dma_begin;
		case ide_dma_end: /* returns 1 on error, 0 otherwise */
			/* TODO: check if something went wrong with the DMA */
			return 0;

                default:
                        printk("e100_dmaproc: unsupported func %d\n", func);
                        return 1;
        }

	/* ATAPI-devices (not disks) first call ide_dma_read/write to set the direction
	 * then they call ide_dma_begin after they have issued the appropriate drive command
	 * themselves to actually start the chipset DMA. so we just return here if we're
	 * not a diskdrive.
	 */

        if (drive->media != ide_disk)
                return 0;

 dma_begin:

	if(reading) {

		RESET_DMA(3); /* sometimes the DMA channel get stuck so we need to do this */
		WAIT_DMA(3);

		/* set up the Etrax DMA descriptors */
		
		if(e100_ide_build_dmatable (drive))
			return 1;

		if(!atapi) {
			/* set the irq handler which will finish the request when DMA is done */
		
			ide_set_handler(drive, &etrax_dma_intr, WAIT_CMD, NULL);
			
			/* issue cmd to drive */
			
			OUT_BYTE(WIN_READDMA, IDE_COMMAND_REG);
		}

		/* begin DMA */
	      
		*R_DMA_CH3_FIRST = virt_to_phys(ata_descrs);
		*R_DMA_CH3_CMD   = IO_STATE(R_DMA_CH3_CMD, cmd, start);
		
		/* initiate a multi word dma read using DMA handshaking */
		
		*R_ATA_TRANSFER_CNT = ata_tot_size >> 1;
		
		*R_ATA_CTRL_DATA = IDE_DATA_REG  |
			IO_STATE(R_ATA_CTRL_DATA, rw,       read) |
			IO_STATE(R_ATA_CTRL_DATA, src_dst,  dma)  |
			IO_STATE(R_ATA_CTRL_DATA, handsh,   dma)  |
			IO_STATE(R_ATA_CTRL_DATA, multi,    on)   |
			IO_STATE(R_ATA_CTRL_DATA, dma_size, word);

		LED_DISK_READ(1);

		D(printk("dma read of %d bytes.\n", ata_tot_size));
 
	} else {
		/* writing */

		RESET_DMA(2); /* sometimes the DMA channel get stuck so we need to do this */
		WAIT_DMA(2);

		/* set up the Etrax DMA descriptors */

		if(e100_ide_build_dmatable (drive))
			return 1;

		if(!atapi) {
			/* set the irq handler which will finish the request when DMA is done */
				
			ide_set_handler(drive, &etrax_dma_intr, WAIT_CMD, NULL);
			
			/* issue cmd to drive */
			
			OUT_BYTE(WIN_WRITEDMA, IDE_COMMAND_REG);
		}

		/* begin DMA */
		
		*R_DMA_CH2_FIRST = virt_to_phys(ata_descrs);
		*R_DMA_CH2_CMD   = IO_STATE(R_DMA_CH2_CMD, cmd, start);
		
		/* initiate a multi word dma write using DMA handshaking */
		
		*R_ATA_TRANSFER_CNT = ata_tot_size >> 1;
		
		*R_ATA_CTRL_DATA = IDE_DATA_REG |
			IO_STATE(R_ATA_CTRL_DATA, rw,       write) |
			IO_STATE(R_ATA_CTRL_DATA, src_dst,  dma) |
			IO_STATE(R_ATA_CTRL_DATA, handsh,   dma) |
			IO_STATE(R_ATA_CTRL_DATA, multi,    on) |
			IO_STATE(R_ATA_CTRL_DATA, dma_size, word);

		LED_DISK_WRITE(1);

		D(printk("dma write of %d bytes.\n", ata_tot_size));
	}

	/* DMA started successfully */
	return 0;
}

/* ide.c calls this, but we don't need to do anything particular */

int ide_release_dma (ide_hwif_t *hwif)
{
	return 1;
}