patch-2.3.99-pre1 linux/drivers/ide/ide-dma.c

• Lines: 581
• Date: Sat Feb 26 20:32:13 2000
• Orig file: v2.3.51/linux/drivers/ide/ide-dma.c
• Orig date: Wed Dec 31 16:00:00 1969

diff -u --recursive --new-file v2.3.51/linux/drivers/ide/ide-dma.c linux/drivers/ide/ide-dma.c
@@ -0,0 +1,580 @@
+/*
+ *  linux/drivers/block/ide-dma.c		Version 4.09	April 23, 1999
+ *
+ *  Copyright (c) 1999  Andre Hedrick
+ *  May be copied or modified under the terms of the GNU General Public License
+ */
+
+/*
+ *  Special Thanks to Mark for his Six years of work.
+ *
+ *  Copyright (c) 1995-1998  Mark Lord
+ *  May be copied or modified under the terms of the GNU General Public License
+ */
+
+/*
+ * 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.
+ *
+ * ACARD ATP850UF Chipset "Modified SCSI Class" with other names
+ *       AEC6210 U/UF
+ *       SIIG's UltraIDE Pro CN-2449
+ * TTI   HPT343 Chipset "Modified SCSI Class" but reports as an
+ *       unknown storage device.
+ * NEW	 check_drive_lists(ide_drive_t *drive, int good_bad)
+ */
+
+#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 <asm/io.h>
+#include <asm/irq.h>
+
+extern char *ide_dmafunc_verbose(ide_dma_action_t dmafunc);
+
+#ifdef CONFIG_IDEDMA_NEW_DRIVE_LISTINGS
+
+struct drive_list_entry {
+	char * id_model;
+	char * id_firmware;
+};
+
+struct drive_list_entry drive_whitelist [] = {
+
+	{ "Micropolis 2112A"	,       "ALL"		},
+	{ "CONNER CTMA 4000"	,       "ALL"		},
+	{ "CONNER CTT8000-A"	,       "ALL"		},
+	{ "ST34342A"		,	"ALL"		},
+	{ 0			,	0		}
+};
+
+struct drive_list_entry drive_blacklist [] = {
+
+	{ "WDC AC11000H"	,	"ALL"		},
+	{ "WDC AC22100H"	,	"ALL"		},
+	{ "WDC AC32500H"	,	"ALL"		},
+	{ "WDC AC33100H"	,	"ALL"		},
+	{ "WDC AC31600H"	,	"ALL"		},
+	{ "WDC AC32100H"	,	"24.09P07"	},
+	{ "WDC AC23200L"	,	"21.10N21"	},
+	{ 0			,	0		}
+
+};
+
+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)) &&
+		    ((!strstr(drive_table->id_firmware, id->fw_rev)) ||
+		     (!strcmp(drive_table->id_firmware, "ALL"))))
+			return 1;
+	return 0;
+}
+
+#else /* !CONFIG_IDEDMA_NEW_DRIVE_LISTINGS */
+
+/*
+ * 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 /* CONFIG_IDEDMA_NEW_DRIVE_LISTINGS */
+
+/*
+ * Our Physical Region Descriptor (PRD) table should be large enough
+ * to handle the biggest I/O request we are likely to see.  Since requests
+ * can have no more than 256 sectors, and since the typical blocksize is
+ * two or more sectors, we could get by with a limit of 128 entries here for
+ * the usual worst case.  Most requests seem to include some contiguous blocks,
+ * further reducing the number of table entries required.
+ *
+ * The driver reverts to PIO mode for individual requests that exceed
+ * this limit (possible with 512 byte blocksizes, eg. MSDOS f/s), so handling
+ * 100% of all crazy scenarios here is not necessary.
+ *
+ * As it turns out though, we must allocate a full 4KB page for this,
+ * so the two PRD tables (ide0 & ide1) will each get half of that,
+ * allowing each to have about 256 entries (8 bytes each) from this.
+ */
+#define PRD_BYTES	8
+#define PRD_ENTRIES	(PAGE_SIZE / (2 * PRD_BYTES))
+
+/*
+ * dma_intr() is the handler for disk read/write DMA interrupts
+ */
+ide_startstop_t ide_dma_intr (ide_drive_t *drive)
+{
+	int i;
+	byte stat, dma_stat;
+
+	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 = HWGROUP(drive)->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: dma_intr: bad DMA status\n", drive->name);
+	}
+	return ide_error(drive, "dma_intr", stat);
+}
+
+static int ide_build_sglist (ide_hwif_t *hwif, struct request *rq)
+{
+	struct buffer_head *bh;
+	struct scatterlist *sg = hwif->sg_table;
+	int nents = 0;
+
+	if (rq->cmd == READ)
+		hwif->sg_dma_direction = PCI_DMA_FROMDEVICE;
+	else
+		hwif->sg_dma_direction = PCI_DMA_TODEVICE;
+	bh = rq->bh;
+	do {
+		unsigned char *virt_addr = bh->b_data;
+		unsigned int size = bh->b_size;
+
+		while ((bh = bh->b_reqnext) != NULL) {
+			if ((virt_addr + size) != (unsigned char *) bh->b_data)
+				break;
+			size += bh->b_size;
+		}
+		memset(&sg[nents], 0, sizeof(*sg));
+		sg[nents].address = virt_addr;
+		sg[nents].length = size;
+		nents++;
+	} while (bh != NULL);
+
+	return pci_map_sg(hwif->pci_dev, sg, nents, hwif->sg_dma_direction);
+}
+
+/*
+ * ide_build_dmatable() prepares a dma request.
+ * Returns 0 if all went okay, returns 1 otherwise.
+ * May also be invoked from trm290.c
+ */
+int ide_build_dmatable (ide_drive_t *drive, ide_dma_action_t func)
+{
+	unsigned int *table = HWIF(drive)->dmatable_cpu;
+#ifdef CONFIG_BLK_DEV_TRM290
+	unsigned int is_trm290_chipset = (HWIF(drive)->chipset == ide_trm290);
+#else
+	const int is_trm290_chipset = 0;
+#endif
+	unsigned int count = 0;
+	int i;
+	struct scatterlist *sg;
+
+	HWIF(drive)->sg_nents = i = ide_build_sglist(HWIF(drive), HWGROUP(drive)->rq);
+
+	sg = HWIF(drive)->sg_table;
+	while (i && sg_dma_len(sg)) {
+		u32 cur_addr;
+		u32 cur_len;
+
+		cur_addr = sg_dma_address(sg);
+		cur_len = sg_dma_len(sg);
+
+		while (cur_len) {
+			if (++count >= PRD_ENTRIES) {
+				printk("%s: DMA table too small\n", drive->name);
+				pci_unmap_sg(HWIF(drive)->pci_dev,
+					     HWIF(drive)->sg_table,
+					     HWIF(drive)->sg_nents,
+					     HWIF(drive)->sg_dma_direction);
+				return 0; /* revert to PIO for this request */
+			} else {
+				u32 xcount, bcount = 0x10000 - (cur_addr & 0xffff);
+
+				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;
+				*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 (ide_drive_t *drive)
+{
+	struct pci_dev *dev = HWIF(drive)->pci_dev;
+	struct scatterlist *sg = HWIF(drive)->sg_table;
+	int nents = HWIF(drive)->sg_nents;
+
+	pci_unmap_sg(dev, sg, nents, HWIF(drive)->sg_dma_direction);
+}
+
+/*
+ *  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;
+}
+
+static int config_drive_for_dma (ide_drive_t *drive)
+{
+	struct hd_driveid *id = drive->id;
+	ide_hwif_t *hwif = HWIF(drive);
+
+	if (id && (id->capability & 1) && hwif->autodma) {
+		/* 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 3/4) enabled */
+		if ((id->field_valid & 4) && (hwif->udma_four) && (id->hw_config & 0x2000))
+			if ((id->dma_ultra & (id->dma_ultra >> 11) & 3))
+				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);
+}
+
+/*
+ * 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)
+{
+	ide_hwif_t *hwif = HWIF(drive);
+	unsigned long dma_base = hwif->dma_base;
+	byte unit = (drive->select.b.unit & 0x01);
+	unsigned int count, reading = 0;
+	byte dma_stat;
+
+	switch (func) {
+		case ide_dma_off:
+			printk("%s: DMA disabled\n", drive->name);
+		case ide_dma_off_quietly:
+			outb(inb(dma_base+2) & ~(1<<(5+unit)), dma_base+2);
+		case ide_dma_on:
+			drive->using_dma = (func == ide_dma_on);
+			if (drive->using_dma)
+				outb(inb(dma_base+2)|(1<<(5+unit)), dma_base+2);
+			return 0;
+		case ide_dma_check:
+			return config_drive_for_dma (drive);
+		case ide_dma_read:
+			reading = 1 << 3;
+		case ide_dma_write:
+			if (!(count = ide_build_dmatable(drive, func)))
+				return 1;	/* try PIO instead of DMA */
+			outl(hwif->dmatable_dma, 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;
+			if (drive->media != ide_disk)
+				return 0;
+			ide_set_handler(drive, &ide_dma_intr, WAIT_CMD, NULL);	/* issue cmd to drive */
+			OUT_BYTE(reading ? WIN_READDMA : WIN_WRITEDMA, IDE_COMMAND_REG);
+		case ide_dma_begin:
+			/* 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;
+		case ide_dma_end: /* returns 1 on error, 0 otherwise */
+			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;	/* verify good DMA status */
+		case ide_dma_test_irq: /* returns 1 if dma irq issued, 0 otherwise */
+			dma_stat = inb(dma_base+2);
+			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_lostirq:
+		case ide_dma_timeout:
+			printk("ide_dmaproc: chipset supported %s func only: %d\n", ide_dmafunc_verbose(func),  func);
+			return 1;
+		default:
+			printk("ide_dmaproc: unsupported %s func: %d\n", ide_dmafunc_verbose(func), func);
+			return 1;
+	}
+}
+
+/*
+ * Needed for allowing full modular support of ide-driver
+ */
+int ide_release_dma (ide_hwif_t *hwif)
+{
+	if (hwif->dmatable_cpu) {
+		pci_free_consistent(hwif->pci_dev,
+				    PRD_ENTRIES * PRD_BYTES,
+				    hwif->dmatable_cpu,
+				    hwif->dmatable_dma);
+		hwif->dmatable_cpu = NULL;
+	}
+	if (hwif->sg_table) {
+		kfree(hwif->sg_table);
+		hwif->sg_table = NULL;
+	}
+	if ((hwif->dma_extra) && (hwif->channel == 0))
+		release_region((hwif->dma_base + 16), hwif->dma_extra);
+	release_region(hwif->dma_base, 8);
+	return 1;
+}
+
+/*
+ *	This can be called for a dynamically installed interface. Don't __init it
+ */
+ 
+void ide_setup_dma (ide_hwif_t *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->dmatable_cpu = pci_alloc_consistent(hwif->pci_dev,
+						  PRD_ENTRIES * PRD_BYTES,
+						  &hwif->dmatable_dma);
+	if (hwif->dmatable_cpu == NULL)
+		goto dma_alloc_failure;
+
+	hwif->sg_table = kmalloc(sizeof(struct scatterlist) * PRD_ENTRIES,
+				 GFP_KERNEL);
+	if (hwif->sg_table == NULL) {
+		pci_free_consistent(hwif->pci_dev, PRD_ENTRIES * PRD_BYTES,
+				    hwif->dmatable_cpu, hwif->dmatable_dma);
+		goto dma_alloc_failure;
+	}
+
+	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;
+
+dma_alloc_failure:
+	printk(" -- ERROR, UNABLE TO ALLOCATE DMA TABLES\n");
+}
+
+/*
+ * Fetch the DMA Bus-Master-I/O-Base-Address (BMIBA) from PCI space:
+ */
+unsigned long __init ide_get_or_set_dma_base (ide_hwif_t *hwif, int extra, const char *name)
+{
+	unsigned long	dma_base = 0;
+	struct pci_dev	*dev = hwif->pci_dev;
+
+	if (hwif->mate && hwif->mate->dma_base) {
+		dma_base = hwif->mate->dma_base - (hwif->channel ? 0 : 8);
+	} else {
+		dma_base = dev->resource[4].start;
+		if (!dma_base || dma_base == PCI_BASE_ADDRESS_IO_MASK) {
+			printk("%s: dma_base is invalid (0x%04lx)\n", name, dma_base);
+			dma_base = 0;
+		}
+	}
+	if (dma_base) {
+		if (extra) /* PDC20246, PDC20262, HPT343, & HPT366 */
+			request_region(dma_base+16, extra, name);
+		dma_base += hwif->channel ? 8 : 0;
+		hwif->dma_extra = extra;
+
+		switch(dev->device) {
+			case PCI_DEVICE_ID_AL_M5219:
+			case PCI_DEVICE_ID_AMD_VIPER_7409:
+			case PCI_DEVICE_ID_CMD_643:
+				outb(inb(dma_base+2) & 0x60, dma_base+2);
+				if (inb(dma_base+2) & 0x80) {
+					printk("%s: simplex device: DMA forced\n", name);
+				}
+				break;
+			default:
+				/*
+				 * If the device claims "simplex" DMA,
+				 * this means only one of the two interfaces
+				 * can be trusted with DMA at any point in time.
+				 * So we should enable DMA only on one of the
+				 * two interfaces.
+				 */
+				if ((inb(dma_base+2) & 0x80)) {	/* simplex device? */
+					if ((!hwif->drives[0].present && !hwif->drives[1].present) ||
+					    (hwif->mate && hwif->mate->dma_base)) {
+						printk("%s: simplex device:  DMA disabled\n", name);
+						dma_base = 0;
+					}
+				}
+		}
+	}
+	return dma_base;
+}