drivers/ide/ide-dma.c

/*
 *  Copyright (c) 1999-2000  Andre Hedrick <andre@linux-ide.org>
 *  Copyright (c) 1995-1998  Mark Lord
 *
 *  May be copied or modified under the terms of the GNU General Public License
 *
 *  Special Thanks to Mark for his Six years of work.
 */

/*
 * This module provides support for the bus-master IDE DMA functions
 * of various PCI chipsets, including the Intel PIIX (i82371FB for
 * the 430 FX chipset), the PIIX3 (i82371SB for the 430 HX/VX and
 * 440 chipsets), and the PIIX4 (i82371AB for the 430 TX chipset)
 * ("PIIX" stands for "PCI ISA IDE Xcellerator").
 *
 * Pretty much the same code works for other IDE PCI bus-mastering chipsets.
 *
 * DMA is supported for all IDE devices (disk drives, cdroms, tapes, floppies).
 *
 * By default, DMA support is prepared for use, but is currently enabled only
 * for drives which already have DMA enabled (UltraDMA or mode 2 multi/single),
 * or which are recognized as "good" (see table below).  Drives with only mode0
 * or mode1 (multi/single) DMA should also work with this chipset/driver
 * (eg. MC2112A) but are not enabled by default.
 *
 * Use "hdparm -i" to view modes supported by a given drive.
 *
 * The hdparm-3.5 (or later) utility can be used for manually enabling/disabling
 * DMA support, but must be (re-)compiled against this kernel version or later.
 *
 * To enable DMA, use "hdparm -d1 /dev/hd?" on a per-drive basis after booting.
 * If problems arise, ide.c will disable DMA operation after a few retries.
 * This error recovery mechanism works and has been extremely well exercised.
 *
 * IDE drives, depending on their vintage, may support several different modes
 * of DMA operation.  The boot-time modes are indicated with a "*" in
 * the "hdparm -i" listing, and can be changed with *knowledgeable* use of
 * the "hdparm -X" feature.  There is seldom a need to do this, as drives
 * normally power-up with their "best" PIO/DMA modes enabled.
 *
 * Testing has been done with a rather extensive number of drives,
 * with Quantum & Western Digital models generally outperforming the pack,
 * and Fujitsu & Conner (and some Seagate which are really Conner) drives
 * showing more lackluster throughput.
 *
 * Keep an eye on /var/adm/messages for "DMA disabled" messages.
 *
 * Some people have reported trouble with Intel Zappa motherboards.
 * This can be fixed by upgrading the AMI BIOS to version 1.00.04.BS0,
 * available from ftp://ftp.intel.com/pub/bios/10004bs0.exe
 * (thanks to Glen Morrell <glen@spin.Stanford.edu> for researching this).
 *
 * Thanks to "Christopher J. Reimer" <reimer@doe.carleton.ca> for
 * fixing the problem with the BIOS on some Acer motherboards.
 *
 * Thanks to "Benoit Poulot-Cazajous" <poulot@chorus.fr> for testing
 * "TX" chipset compatibility and for providing patches for the "TX" chipset.
 *
 * Thanks to Christian Brunner <chb@muc.de> for taking a good first crack
 * at generic DMA -- his patches were referred to when preparing this code.
 *
 * Most importantly, thanks to Robert Bringman <rob@mars.trion.com>
 * for supplying a Promise UDMA board & WD UDMA drive for this work!
 *
 * And, yes, Intel Zappa boards really *do* use both PIIX IDE ports.
 *
 * check_drive_lists(ide_drive_t *drive, int good_bad)
 *
 * ATA-66/100 and recovery functions, I forgot the rest......
 */

#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/pci.h>
#include <linux/init.h>
#include <linux/ide.h>
#include <linux/delay.h>

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

/*
 * Long lost data from 2.0.34 that is now in 2.0.39
 *
 * This was used in ./drivers/block/triton.c to do DMA Base address setup
 * when PnP failed.  Oh the things we forget.  I believe this was part
 * of SFF-8038i that has been withdrawn from public access... :-((
 */
#define DEFAULT_BMIBA	0xe800	/* in case BIOS did not init it */
#define DEFAULT_BMCRBA	0xcc00	/* VIA's default value */
#define DEFAULT_BMALIBA	0xd400	/* ALI's default value */

#ifdef CONFIG_IDEDMA_NEW_DRIVE_LISTINGS

struct drive_list_entry {
	char * id_model;
	char * id_firmware;
};

struct drive_list_entry drive_whitelist[] = {
	{ "Micropolis 2112A", NULL },
	{ "CONNER CTMA 4000", NULL },
	{ "CONNER CTT8000-A", NULL },
	{ "ST34342A", NULL },
	{ NULL, NULL }
};

struct drive_list_entry drive_blacklist[] = {

	{ "WDC AC11000H", NULL },
	{ "WDC AC22100H", NULL },
	{ "WDC AC32500H", NULL },
	{ "WDC AC33100H", NULL },
	{ "WDC AC31600H", NULL },
	{ "WDC AC32100H", "24.09P07" },
	{ "WDC AC23200L", "21.10N21" },
	{ "Compaq CRD-8241B", NULL },
	{ "CRD-8400B", NULL },
	{ "CRD-8480B", NULL },
	{ "CRD-8480C", NULL },
	{ "CRD-8482B", NULL },
	{ "CRD-84", NULL },
	{ "SanDisk SDP3B", NULL },
	{ "SanDisk SDP3B-64", NULL },
	{ "SANYO CD-ROM CRD", NULL },
	{ "HITACHI CDR-8", NULL },
	{ "HITACHI CDR-8335", NULL },
	{ "HITACHI CDR-8435", NULL },
	{ "Toshiba CD-ROM XM-6202B", NULL },
	{ "CD-532E-A", NULL },
	{ "E-IDE CD-ROM CR-840", NULL },
	{ "CD-ROM Drive/F5A", NULL },
	{ "RICOH CD-R/RW MP7083A", NULL },
	{ "WPI CDD-820", NULL },
	{ "SAMSUNG CD-ROM SC-148C", NULL },
	{ "SAMSUNG CD-ROM SC-148F", NULL },
	{ "SAMSUNG CD-ROM SC", NULL },
	{ "SanDisk SDP3B-64", NULL },
	{ "SAMSUNG CD-ROM SN-124", NULL },
	{ "PLEXTOR CD-R PX-W8432T", NULL },
	{ "ATAPI CD-ROM DRIVE 40X MAXIMUM", NULL },
	{ "_NEC DV5800A", NULL },
	{ NULL,	NULL }

};

static int in_drive_list(struct hd_driveid *id, struct drive_list_entry * drive_table)
{
	for ( ; drive_table->id_model ; drive_table++)
		if ((!strcmp(drive_table->id_model, id->model)) &&
		    ((drive_table->id_firmware && !strstr(drive_table->id_firmware, id->fw_rev)) ||
		     (!drive_table->id_firmware)))
			return 1;
	return 0;
}

#else

/*
 * good_dma_drives() lists the model names (from "hdparm -i")
 * of drives which do not support mode2 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",
				 "ST34342A",	/* for Sun Ultra */
				 NULL};

/*
 * bad_dma_drives() lists the model names (from "hdparm -i")
 * of drives which supposedly support (U)DMA but which are
 * known to corrupt data with this interface under Linux.
 *
 * This is an empirical list. Its generated from bug reports. That means
 * while it reflects actual problem distributions it doesn't answer whether
 * the drive or the controller, or cabling, or software, or some combination
 * thereof is the fault. If you don't happen to agree with the kernel's
 * opinion of your drive - use hdparm to turn DMA on.
 */
const char *bad_dma_drives[] = {"WDC AC11000H",
				"WDC AC22100H",
				"WDC AC32100H",
				"WDC AC32500H",
				"WDC AC33100H",
				"WDC AC31600H",
				NULL};

#endif

/*
 * dma_intr() is the handler for disk read/write DMA interrupts
 */
ide_startstop_t ide_dma_intr (ide_drive_t *drive)
{
	byte stat, dma_stat;

	dma_stat = drive->channel->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 = HWGROUP(drive)->rq;

			__ide_end_request(drive, 1, rq->nr_sectors);
			return ide_stopped;
		}
		printk("%s: dma_intr: bad DMA status (dma_stat=%x)\n",
		       drive->name, dma_stat);
	}
	return ide_error(drive, "dma_intr", stat);
}

int ide_build_sglist(struct ata_channel *hwif, struct request *rq)
{
	request_queue_t *q = &hwif->drives[DEVICE_NR(rq->rq_dev) & 1].queue;
	struct ata_request *ar = rq->special;

	if (!(ar->ar_flags & ATA_AR_SETUP)) {
		ar->ar_flags |= ATA_AR_SETUP;
		ar->ar_sg_nents = blk_rq_map_sg(q, rq, ar->ar_sg_table);
	}

	if (rq->q && ar->ar_sg_nents > rq->nr_phys_segments) {
		printk("%s: received %d phys segments, build %d\n", __FILE__, rq->nr_phys_segments, ar->ar_sg_nents);
		return 0;
	} else if (!ar->ar_sg_nents) {
		printk("%s: zero segments in request\n", __FILE__);
		return 0;
	}

	if (rq_data_dir(rq) == READ)
		ar->ar_sg_ddir = PCI_DMA_FROMDEVICE;
	else
		ar->ar_sg_ddir = PCI_DMA_TODEVICE;

	return pci_map_sg(hwif->pci_dev, ar->ar_sg_table, ar->ar_sg_nents, ar->ar_sg_ddir);
}

/*
 * FIXME: taskfiles should be a map of pages, not a long virt address... /jens
 * FIXME: I agree with Jens --mdcki!
 */
static int raw_build_sglist(struct ata_channel *ch, struct request *rq)
{
	struct ata_request *ar = rq->special;
	struct scatterlist *sg = ar->ar_sg_table;
	struct ata_taskfile *args = &ar->ar_task;
	unsigned char *virt_addr = rq->buffer;
	int sector_count = rq->nr_sectors;
	int nents = 0;

	if (args->command_type == IDE_DRIVE_TASK_RAW_WRITE)
		ar->ar_sg_ddir = PCI_DMA_TODEVICE;
	else
		ar->ar_sg_ddir = PCI_DMA_FROMDEVICE;

	if (sector_count > 128) {
		memset(&sg[nents], 0, sizeof(*sg));

		sg[nents].page = virt_to_page(virt_addr);
		sg[nents].offset = (unsigned long) virt_addr & ~PAGE_MASK;
		sg[nents].length = 128  * SECTOR_SIZE;
		nents++;
		virt_addr = virt_addr + (128 * SECTOR_SIZE);
		sector_count -= 128;
	}
	memset(&sg[nents], 0, sizeof(*sg));
	sg[nents].page = virt_to_page(virt_addr);
	sg[nents].offset = (unsigned long) virt_addr & ~PAGE_MASK;
	sg[nents].length =  sector_count  * SECTOR_SIZE;
	nents++;

	return pci_map_sg(ch->pci_dev, sg, nents, ar->ar_sg_ddir);
}

/*
 * Prepare a dma request.
 * Returns 0 if all went okay, returns 1 otherwise.
 * This may also be invoked from trm290.c
 */
int ide_build_dmatable(ide_drive_t *drive, struct request *rq,
		       ide_dma_action_t func)
{
	struct ata_channel *hwif = drive->channel;
#ifdef CONFIG_BLK_DEV_TRM290
	unsigned int is_trm290_chipset = (hwif->chipset == ide_trm290);
#else
	const int is_trm290_chipset = 0;
#endif
	unsigned int count = 0;
	int i;
	struct scatterlist *sg;
	struct ata_request *ar = rq->special;
	unsigned int *table = ar->ar_dmatable_cpu;

	if (rq->flags & REQ_DRIVE_TASKFILE)
		ar->ar_sg_nents = raw_build_sglist(hwif, rq);
	else
		ar->ar_sg_nents = ide_build_sglist(hwif, rq);

	if (!ar->ar_sg_nents)
		return 0;

	sg = ar->ar_sg_table;
	i = ar->ar_sg_nents;
	while (i) {
		u32 cur_addr;
		u32 cur_len;

		cur_addr = sg_dma_address(sg);
		cur_len = sg_dma_len(sg);

		/*
		 * Fill in the dma table, without crossing any 64kB boundaries.
		 * Most hardware requires 16-bit alignment of all blocks,
		 * but the trm290 requires 32-bit alignment.
		 */

		while (cur_len) {
			u32 xcount, bcount = 0x10000 - (cur_addr & 0xffff);

			if (count++ >= PRD_ENTRIES) {
				printk("ide-dma: req %p\n", HWGROUP(drive)->rq);
				printk("count %d, sg_nents %d, cur_len %d, cur_addr %u\n", count, ar->ar_sg_nents, cur_len, cur_addr);
				BUG();
			}

			if (bcount > cur_len)
				bcount = cur_len;
			*table++ = cpu_to_le32(cur_addr);
			xcount = bcount & 0xffff;
			if (is_trm290_chipset)
				xcount = ((xcount >> 2) - 1) << 16;
			if (xcount == 0x0000) {
		        /*
			 * Most chipsets correctly interpret a length of
			 * 0x0000 as 64KB, but at least one (e.g. CS5530)
			 * misinterprets it as zero (!). So here we break
			 * the 64KB entry into two 32KB entries instead.
			 */
				if (count++ >= PRD_ENTRIES) {
					pci_unmap_sg(hwif->pci_dev, sg,
						     ar->ar_sg_nents,
						     ar->ar_sg_ddir);
					return 0;
				}

				*table++ = cpu_to_le32(0x8000);
				*table++ = cpu_to_le32(cur_addr + 0x8000);
				xcount = 0x8000;
			}
			*table++ = cpu_to_le32(xcount);
			cur_addr += bcount;
			cur_len -= bcount;
		}

		sg++;
		i--;
	}

	if (!count)
		printk("%s: empty DMA table?\n", drive->name);
	else if (!is_trm290_chipset)
		*--table |= cpu_to_le32(0x80000000);

	return count;
}

/* Teardown mappings after DMA has completed.  */
void ide_destroy_dmatable(struct ata_device *d)
{
	struct pci_dev *dev = d->channel->pci_dev;
	struct ata_request *ar = IDE_CUR_AR(d);

	pci_unmap_sg(dev, ar->ar_sg_table, ar->ar_sg_nents, ar->ar_sg_ddir);
}

/*
 *  For both Blacklisted and Whitelisted drives.
 *  This is setup to be called as an extern for future support
 *  to other special driver code.
 */
int check_drive_lists (ide_drive_t *drive, int good_bad)
{
	struct hd_driveid *id = drive->id;

#ifdef CONFIG_IDEDMA_NEW_DRIVE_LISTINGS
	if (good_bad) {
		return in_drive_list(id, drive_whitelist);
	} else {
		int blacklist = in_drive_list(id, drive_blacklist);
		if (blacklist)
			printk("%s: Disabling (U)DMA for %s\n", drive->name, id->model);
		return(blacklist);
	}
#else /* !CONFIG_IDEDMA_NEW_DRIVE_LISTINGS */
	const char **list;

	if (good_bad) {
		/* Consult the list of known "good" drives */
		list = good_dma_drives;
		while (*list) {
			if (!strcmp(*list++,id->model))
				return 1;
		}
	} else {
		/* Consult the list of known "bad" drives */
		list = bad_dma_drives;
		while (*list) {
			if (!strcmp(*list++,id->model)) {
				printk("%s: Disabling (U)DMA for %s\n",
					drive->name, id->model);
				return 1;
			}
		}
	}
#endif /* CONFIG_IDEDMA_NEW_DRIVE_LISTINGS */
	return 0;
}

int report_drive_dmaing (ide_drive_t *drive)
{
	struct hd_driveid *id = drive->id;

	if ((id->field_valid & 4) && (eighty_ninty_three(drive)) &&
	    (id->dma_ultra & (id->dma_ultra >> 14) & 3)) {
		if ((id->dma_ultra >> 15) & 1) {
			printk(", UDMA(mode 7)");	/* UDMA BIOS-enabled! */
		} else {
			printk(", UDMA(133)");	/* UDMA BIOS-enabled! */
		}
	} else if ((id->field_valid & 4) && (eighty_ninty_three(drive)) &&
		  (id->dma_ultra & (id->dma_ultra >> 11) & 7)) {
		if ((id->dma_ultra >> 13) & 1) {
			printk(", UDMA(100)");	/* UDMA BIOS-enabled! */
		} else if ((id->dma_ultra >> 12) & 1) {
			printk(", UDMA(66)");	/* UDMA BIOS-enabled! */
		} else {
			printk(", UDMA(44)");	/* UDMA BIOS-enabled! */
		}
	} else if ((id->field_valid & 4) &&
		   (id->dma_ultra & (id->dma_ultra >> 8) & 7)) {
		if ((id->dma_ultra >> 10) & 1) {
			printk(", UDMA(33)");	/* UDMA BIOS-enabled! */
		} else if ((id->dma_ultra >> 9) & 1) {
			printk(", UDMA(25)");	/* UDMA BIOS-enabled! */
		} else {
			printk(", UDMA(16)");	/* UDMA BIOS-enabled! */
		}
	} else if (id->field_valid & 4) {
		printk(", (U)DMA");	/* Can be BIOS-enabled! */
	} else {
		printk(", DMA");
	}
	return 1;
}

static int config_drive_for_dma (ide_drive_t *drive)
{
	int config_allows_dma = 1;
	struct hd_driveid *id = drive->id;
	struct ata_channel *hwif = drive->channel;

#ifdef CONFIG_IDEDMA_ONLYDISK
	if (drive->type != ATA_DISK)
		config_allows_dma = 0;
#endif

	if (id && (id->capability & 1) && hwif->autodma && config_allows_dma) {
		/* Consult the list of known "bad" drives */
		if (ide_dmaproc(ide_dma_bad_drive, drive))
			return hwif->dmaproc(ide_dma_off, drive);

		/* Enable DMA on any drive that has UltraDMA (mode 6/7/?) enabled */
		if ((id->field_valid & 4) && (eighty_ninty_three(drive)))
			if ((id->dma_ultra & (id->dma_ultra >> 14) & 2))
				return hwif->dmaproc(ide_dma_on, drive);
		/* Enable DMA on any drive that has UltraDMA (mode 3/4/5) enabled */
		if ((id->field_valid & 4) && (eighty_ninty_three(drive)))
			if ((id->dma_ultra & (id->dma_ultra >> 11) & 7))
				return hwif->dmaproc(ide_dma_on, drive);
		/* Enable DMA on any drive that has UltraDMA (mode 0/1/2) enabled */
		if (id->field_valid & 4)	/* UltraDMA */
			if ((id->dma_ultra & (id->dma_ultra >> 8) & 7))
				return hwif->dmaproc(ide_dma_on, drive);
		/* Enable DMA on any drive that has mode2 DMA (multi or single) enabled */
		if (id->field_valid & 2)	/* regular DMA */
			if ((id->dma_mword & 0x404) == 0x404 || (id->dma_1word & 0x404) == 0x404)
				return hwif->dmaproc(ide_dma_on, drive);
		/* Consult the list of known "good" drives */
		if (ide_dmaproc(ide_dma_good_drive, drive))
			return hwif->dmaproc(ide_dma_on, drive);
	}
	return hwif->dmaproc(ide_dma_off_quietly, drive);
}

/*
 * 1 dma-ing, 2 error, 4 intr
 */
static int dma_timer_expiry(ide_drive_t *drive)
{
	byte dma_stat = inb(drive->channel->dma_base+2);

#ifdef DEBUG
	printk("%s: dma_timer_expiry: dma status == 0x%02x\n", drive->name, dma_stat);
#endif /* DEBUG */

#if 0
	HWGROUP(drive)->expiry = NULL;	/* one free ride for now */
#endif

	if (dma_stat & 2) {	/* ERROR */
		byte stat = GET_STAT();
		return ide_error(drive, "dma_timer_expiry", stat);
	}
	if (dma_stat & 1)	/* DMAing */
		return WAIT_CMD;
	return 0;
}

static void ide_toggle_bounce(ide_drive_t *drive, int on)
{
	u64 addr = BLK_BOUNCE_HIGH;

	if (on && drive->type == ATA_DISK && drive->channel->highmem) {
		if (!PCI_DMA_BUS_IS_PHYS)
			addr = BLK_BOUNCE_ANY;
		else
			addr = drive->channel->pci_dev->dma_mask;
	}

	blk_queue_bounce_limit(&drive->queue, addr);
}

/*
 * Start DMA engine.
 */
int ide_start_dma(struct ata_channel *hwif, ide_drive_t *drive, ide_dma_action_t func)
{
	unsigned int reading = 0, count;
	unsigned long dma_base = hwif->dma_base;
	struct ata_request *ar = IDE_CUR_AR(drive);

	/* This can happen with drivers abusing the special request field.
	 */

	if (!ar) {
		printk(KERN_ERR "DMA without ATA request\n");

		return 1;
	}

	if (rq_data_dir(ar->ar_rq) == READ)
		reading = 1 << 3;

	if (hwif->rwproc)
		hwif->rwproc(drive, func);

	if (!(count = ide_build_dmatable(drive, ar->ar_rq, func)))
		return 1;	/* try PIO instead of DMA */

	ar->ar_flags |= ATA_AR_SETUP;
	outl(ar->ar_dmatable, dma_base + 4);	/* PRD table */
	outb(reading, dma_base);		/* specify r/w */
	outb(inb(dma_base + 2) | 6, dma_base+2);/* clear INTR & ERROR flags */
	drive->waiting_for_dma = 1;
	return 0;
}

/*
 * ide_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.
 * May also be invoked from trm290.c
 */
int ide_dmaproc (ide_dma_action_t func, ide_drive_t *drive)
{
	struct ata_channel *hwif = drive->channel;
	unsigned long dma_base = hwif->dma_base;
	u8 unit = (drive->select.b.unit & 0x01);
	unsigned int reading = 0, set_high = 1;
	struct ata_request *ar;
	u8 dma_stat;

	switch (func) {
		case ide_dma_off:
			printk("%s: DMA disabled\n", drive->name);
		case ide_dma_off_quietly:
			set_high = 0;
			outb(inb(dma_base+2) & ~(1<<(5+unit)), dma_base+2);
#ifdef CONFIG_BLK_DEV_IDE_TCQ
			hwif->dmaproc(ide_dma_queued_off, drive);
#endif
		case ide_dma_on:
			ide_toggle_bounce(drive, set_high);
			drive->using_dma = (func == ide_dma_on);
			if (drive->using_dma) {
				outb(inb(dma_base+2)|(1<<(5+unit)), dma_base+2);
#ifdef CONFIG_BLK_DEV_IDE_TCQ_DEFAULT
				hwif->dmaproc(ide_dma_queued_on, drive);
#endif
			}
			return 0;
		case ide_dma_check:
			return config_drive_for_dma (drive);
		case ide_dma_begin:
			if (test_and_set_bit(IDE_DMA, &HWGROUP(drive)->flags))
				BUG();
			/* Note that this is done *after* the cmd has
			 * been issued to the drive, as per the BM-IDE spec.
			 * The Promise Ultra33 doesn't work correctly when
			 * we do this part before issuing the drive cmd.
			 */
			outb(inb(dma_base)|1, dma_base);		/* start DMA */
			return 0;
#ifdef CONFIG_BLK_DEV_IDE_TCQ
		case ide_dma_queued_on:
		case ide_dma_queued_off:
		case ide_dma_read_queued:
		case ide_dma_write_queued:
		case ide_dma_queued_start:
			return ide_tcq_dmaproc(func, drive);
#endif

		case ide_dma_read:
			reading = 1 << 3;
		case ide_dma_write:
			ar = IDE_CUR_AR(drive);

			if (ide_start_dma(hwif, drive, func))
				return 1;

			if (drive->type != ATA_DISK)
				return 0;
			BUG_ON(HWGROUP(drive)->handler);
			ide_set_handler(drive, &ide_dma_intr, WAIT_CMD, dma_timer_expiry);	/* issue cmd to drive */
			if ((ar->ar_rq->flags & REQ_DRIVE_TASKFILE) &&
			    (drive->addressing == 1)) {
				struct ata_taskfile *args = &ar->ar_task;
				OUT_BYTE(args->taskfile.command, IDE_COMMAND_REG);
			} else if (drive->addressing) {
				OUT_BYTE(reading ? WIN_READDMA_EXT : WIN_WRITEDMA_EXT, IDE_COMMAND_REG);
			} else {
				OUT_BYTE(reading ? WIN_READDMA : WIN_WRITEDMA, IDE_COMMAND_REG);
			}
			return hwif->dmaproc(ide_dma_begin, drive);
		case ide_dma_end: /* returns 1 on error, 0 otherwise */
			if (!test_and_clear_bit(IDE_DMA, &HWGROUP(drive)->flags))
				BUG();
			drive->waiting_for_dma = 0;
			outb(inb(dma_base)&~1, dma_base);	/* stop DMA */
			dma_stat = inb(dma_base+2);	/* get DMA status */
			outb(dma_stat|6, dma_base+2);	/* clear the INTR & ERROR bits */
			ide_destroy_dmatable(drive);	/* purge DMA mappings */
			return (dma_stat & 7) != 4 ? (0x10 | dma_stat) : 0;	/* verify good DMA status */
		case ide_dma_test_irq: /* returns 1 if dma irq issued, 0 otherwise */
			dma_stat = inb(dma_base+2);
#if 0  /* do not set unless you know what you are doing */
			if (dma_stat & 4) {
				byte stat = GET_STAT();
				outb(dma_base+2, dma_stat & 0xE4);
			}
#endif
			return (dma_stat & 4) == 4;	/* return 1 if INTR asserted */
		case ide_dma_bad_drive:
		case ide_dma_good_drive:
			return check_drive_lists(drive, (func == ide_dma_good_drive));
		case ide_dma_verbose:
			return report_drive_dmaing(drive);
		case ide_dma_timeout:
			printk(KERN_ERR "%s: DMA timeout occured!\n", __FUNCTION__);
			return 1;
		case ide_dma_retune:
		case ide_dma_lostirq:
			printk(KERN_ERR "%s: chipset supported func only: %d\n", __FUNCTION__, func);
			return 1;
		default:
			printk(KERN_ERR "%s: unsupported func: %d\n", __FUNCTION__, func);
			return 1;
	}
}

/*
 * Needed for allowing full modular support of ide-driver
 */
void ide_release_dma(struct ata_channel *hwif)
{
	if (!hwif->dma_base)
		return;

	if ((hwif->dma_extra) && (hwif->unit == 0))
		release_region((hwif->dma_base + 16), hwif->dma_extra);
	release_region(hwif->dma_base, 8);
	hwif->dma_base = 0;
}

/*
 * This can be called for a dynamically installed interface. Don't __init it
 */
void ide_setup_dma(struct ata_channel *hwif, unsigned long dma_base, unsigned int num_ports)
{
	printk("    %s: BM-DMA at 0x%04lx-0x%04lx", hwif->name, dma_base, dma_base + num_ports - 1);
	if (check_region(dma_base, num_ports)) {
		printk(" -- ERROR, PORT ADDRESSES ALREADY IN USE\n");
		return;
	}
	request_region(dma_base, num_ports, hwif->name);
	hwif->dma_base = dma_base;
	hwif->dmaproc = &ide_dmaproc;

	if (hwif->chipset != ide_trm290) {
		byte dma_stat = inb(dma_base+2);
		printk(", BIOS settings: %s:%s, %s:%s",
		       hwif->drives[0].name, (dma_stat & 0x20) ? "DMA" : "pio",
		       hwif->drives[1].name, (dma_stat & 0x40) ? "DMA" : "pio");
	}
	printk("\n");
	return;
}