首页 > 代码库 > include/asm/dma.h
include/asm/dma.h
/* $Id: dma.h,v 1.7 1992/12/14 00:29:34 root Exp root $
* linux/include/asm/dma.h: Defines for using and allocating dma channels.
* Written by Hennus Bergman, 1992.
* High DMA channel support & info by Hannu Savolainen
* and John Boyd, Nov. 1992.
*/
#ifndef _ASM_DMA_H
#define _ASM_DMA_H
#include <asm/io.h> /* need byte IO */
#ifdef HAVE_REALLY_SLOW_DMA_CONTROLLER
#define outb outb_p
#endif
/*
* NOTES about DMA transfers:
*
* controller 1: channels 0-3, byte operations, ports 00-1F
* controller 2: channels 4-7, word operations, ports C0-DF
*
* - ALL registers are 8 bits only, regardless of transfer size
* - channel 4 is not used - cascades 1 into 2.
* - channels 0-3 are byte - addresses/counts are for physical bytes
* - channels 5-7 are word - addresses/counts are for physical words
* - transfers must not cross physical 64K (0-3) or 128K (5-7) boundaries
* - transfer count loaded to registers is 1 less than actual count
* - controller 2 offsets are all even (2x offsets for controller 1)
* - page registers for 5-7 don‘t use data bit 0, represent 128K pages
* - page registers for 0-3 use bit 0, represent 64K pages
*
* DMA transfers are limited to the lower 16MB of _physical_ memory.
* Note that addresses loaded into registers must be _physical_ addresses,
* not logical addresses (which may differ if paging is active).
*
* Address mapping for channels 0-3:
*
* A23 ... A16 A15 ... A8 A7 ... A0 (Physical addresses)
* | ... | | ... | | ... |
* | ... | | ... | | ... |
* | ... | | ... | | ... |
* P7 ... P0 A7 ... A0 A7 ... A0
* | Page | Addr MSB | Addr LSB | (DMA registers)
*
* Address mapping for channels 5-7:
*
* A23 ... A17 A16 A15 ... A9 A8 A7 ... A1 A0 (Physical addresses)
* | ... | \ \ ... \ \ \ ... \ \
* | ... | \ \ ... \ \ \ ... \ (not used)
* | ... | \ \ ... \ \ \ ... \
* P7 ... P1 (0) A7 A6 ... A0 A7 A6 ... A0
* | Page | Addr MSB | Addr LSB | (DMA registers)
*
* Again, channels 5-7 transfer _physical_ words (16 bits), so addresses
* and counts _must_ be word-aligned (the lowest address bit is _ignored_ at
* the hardware level, so odd-byte transfers aren‘t possible).
*
* Transfer count (_not # bytes_) is limited to 64K, represented as actual
* count - 1 : 64K => 0xFFFF, 1 => 0x0000. Thus, count is always 1 or more,
* and up to 128K bytes may be transferred on channels 5-7 in one operation.
*
*/
#define MAX_DMA_CHANNELS 8
/* 8237 DMA controllers */
#define IO_DMA1_BASE 0x00 /* 8 bit slave DMA, channels 0..3 */
#define IO_DMA2_BASE 0xC0 /* 16 bit master DMA, ch 4(=slave input)..7 */
/* DMA controller registers */
#define DMA1_CMD_REG 0x08 /* command register (w) */
#define DMA1_STAT_REG 0x08 /* status register (r) */
#define DMA1_REQ_REG 0x09 /* request register (w) */
#define DMA1_MASK_REG 0x0A /* single-channel mask (w) */
#define DMA1_MODE_REG 0x0B /* mode register (w) */
#define DMA1_CLEAR_FF_REG 0x0C /* clear pointer flip-flop (w) */
#define DMA1_TEMP_REG 0x0D /* Temporary Register (r) */
#define DMA1_RESET_REG 0x0D /* Master Clear (w) */
#define DMA1_CLR_MASK_REG 0x0E /* Clear Mask */
#define DMA1_MASK_ALL_REG 0x0F /* all-channels mask (w) */
#define DMA2_CMD_REG 0xD0 /* command register (w) */
#define DMA2_STAT_REG 0xD0 /* status register (r) */
#define DMA2_REQ_REG 0xD2 /* request register (w) */
#define DMA2_MASK_REG 0xD4 /* single-channel mask (w) */
#define DMA2_MODE_REG 0xD6 /* mode register (w) */
#define DMA2_CLEAR_FF_REG 0xD8 /* clear pointer flip-flop (w) */
#define DMA2_TEMP_REG 0xDA /* Temporary Register (r) */
#define DMA2_RESET_REG 0xDA /* Master Clear (w) */
#define DMA2_CLR_MASK_REG 0xDC /* Clear Mask */
#define DMA2_MASK_ALL_REG 0xDE /* all-channels mask (w) */
#define DMA_ADDR_0 0x00 /* DMA address registers */
#define DMA_ADDR_1 0x02
#define DMA_ADDR_2 0x04
#define DMA_ADDR_3 0x06
#define DMA_ADDR_4 0xC0
#define DMA_ADDR_5 0xC4
#define DMA_ADDR_6 0xC8
#define DMA_ADDR_7 0xCC
#define DMA_CNT_0 0x01 /* DMA count registers */
#define DMA_CNT_1 0x03
#define DMA_CNT_2 0x05
#define DMA_CNT_3 0x07
#define DMA_CNT_4 0xC2
#define DMA_CNT_5 0xC6
#define DMA_CNT_6 0xCA
#define DMA_CNT_7 0xCE
#define DMA_PAGE_0 0x87 /* DMA page registers */
#define DMA_PAGE_1 0x83
#define DMA_PAGE_2 0x81
#define DMA_PAGE_3 0x82
#define DMA_PAGE_5 0x8B
#define DMA_PAGE_6 0x89
#define DMA_PAGE_7 0x8A
#define DMA_MODE_READ 0x44 /* I/O to memory, no autoinit, increment, single mode */
#define DMA_MODE_WRITE 0x48 /* memory to I/O, no autoinit, increment, single mode */
#define DMA_MODE_CASCADE 0xC0 /* pass thru DREQ->HRQ, DACK<-HLDA only */
/* enable/disable a specific DMA channel */
//启用指定的DMA通道，实际上就是向指定的端口写命令字
static __inline__ void enable_dma(unsigned int dmanr)
{
if (dmanr<=3)
outb(dmanr, DMA1_MASK_REG);
else
outb(dmanr & 3, DMA2_MASK_REG);
}
//禁止指定的DMA通道，实际上就是向指定的端口写命令字
static __inline__ void disable_dma(unsigned int dmanr)
{
if (dmanr<=3)
outb(dmanr | 4, DMA1_MASK_REG);
else
outb((dmanr & 3) | 4, DMA2_MASK_REG);
}
/* Clear the ‘DMA Pointer Flip Flop‘.
* Write 0 for LSB/MSB, 1 for MSB/LSB access.
* Use this once to initialize the FF to a known state.
* After that, keep track of it. :-)
* --- In order to do that, the DMA routines below should ---
* --- only be used while interrupts are disabled! ---
*/
//初始化Flip Flop
static __inline__ void clear_dma_ff(unsigned int dmanr)
{
if (dmanr<=3)
outb(0, DMA1_CLEAR_FF_REG);
else
outb(0, DMA2_CLEAR_FF_REG);
}
/* set mode (above) for a specific DMA channel */
//为指定的DMA通道设置模式
static __inline__ void set_dma_mode(unsigned int dmanr, char mode)
{
if (dmanr<=3)
outb(mode | dmanr, DMA1_MODE_REG);
else
outb(mode | (dmanr&3), DMA2_MODE_REG);
}
/* Set only the page register bits of the transfer address.
* This is used for successive transfers when we know the contents of
* the lower 16 bits of the DMA current address register, but a 64k boundary
* may have been crossed.
*/
static __inline__ void set_dma_page(unsigned int dmanr, char pagenr)
{
switch(dmanr) {
case 0:
outb(pagenr, DMA_PAGE_0);
break;
case 1:
outb(pagenr, DMA_PAGE_1);
break;
case 2:
outb(pagenr, DMA_PAGE_2);
break;
case 3:
outb(pagenr, DMA_PAGE_3);
break;
case 5:
outb(pagenr & 0xfe, DMA_PAGE_5);
break;
case 6:
outb(pagenr & 0xfe, DMA_PAGE_6);
break;
case 7:
outb(pagenr & 0xfe, DMA_PAGE_7);
break;
}
}
/* Set transfer address & page bits for specific DMA channel.
* Assumes dma flipflop is clear.
*/
//设置dma的传输地址
static __inline__ void set_dma_addr(unsigned int dmanr, unsigned int a)
{
set_dma_page(dmanr, a>>16);
if (dmanr <= 3) {
outb( a & 0xff, ((dmanr&3)<<1) + IO_DMA1_BASE );
outb( (a>>8) & 0xff, ((dmanr&3)<<1) + IO_DMA1_BASE );
} else {
outb( (a>>1) & 0xff, ((dmanr&3)<<2) + IO_DMA2_BASE );
outb( (a>>9) & 0xff, ((dmanr&3)<<2) + IO_DMA2_BASE );
}
}
/* Set transfer size (max 64k for DMA1..3, 128k for DMA5..7) for
* a specific DMA channel.
* You must ensure the parameters are valid.
* NOTE: from a manual: "the number of transfers is one more
* than the initial word count"! This is taken into account.
* Assumes dma flip-flop is clear.
* NOTE 2: "count" represents _bytes_ and must be even for channels 5-7.
*/
//设置dma的传输长度
static __inline__ void set_dma_count(unsigned int dmanr, unsigned int count)
{
count--;
if (dmanr <= 3) {
outb( count & 0xff, ((dmanr&3)<<1) + 1 + IO_DMA1_BASE );
outb( (count>>8) & 0xff, ((dmanr&3)<<1) + 1 + IO_DMA1_BASE );
} else {
outb( (count>>1) & 0xff, ((dmanr&3)<<2) + 2 + IO_DMA2_BASE );
outb( (count>>9) & 0xff, ((dmanr&3)<<2) + 2 + IO_DMA2_BASE );
}
}
/* Get DMA residue count. After a DMA transfer, this
* should return zero. Reading this while a DMA transfer is
* still in progress will return unpredictable results.
* If called before the channel has been used, it may return 1.
* Otherwise, it returns the number of _bytes_ left to transfer.
*
* Assumes DMA flip-flop is clear.
*/
//获取dma传输剩余长度
static __inline__ int get_dma_residue(unsigned int dmanr)
{
unsigned int io_port = (dmanr<=3)? ((dmanr&3)<<1) + 1 + IO_DMA1_BASE
: ((dmanr&3)<<2) + 2 + IO_DMA2_BASE;
/* using short to get 16-bit wrap around */
unsigned short count;
count = 1 + inb(io_port);
count += inb(io_port) << 8;
return (dmanr<=3)? count : (count<<1);
}
/* These are in kernel/dma.c: */
extern int request_dma(unsigned int dmanr); /* reserve a DMA channel */
extern void free_dma(unsigned int dmanr); /* release it again */
#endif /* _ASM_DMA_H */