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On 23/06/2016 09:02, Yanjun Yang wrote:
Hi,
I was trying to use DMA to transfer a sector of data from
hardisk to memory. The attached
code works under VirtualBox (change bmcr address to D000) but
not under newer version
of qemu. An old version of qemu (1.1.2 from Debian wheezy)
behave as I expected. Other
version I tested are 2.5.1.1 from stable branch, 2.6.50
from Arch Linux, they both give all
zero result.
The following code was compiled by Jwasm(MASM compatible)
under dos. It'll display the
first sector of data from disk on screen. I don't know
whether there is bugs in my code or
I miss a configuration of qemu.
To test my code, I just used a clean install of FreeDos,
and run the executable compiled by
Jwasm. I didn't use any special qemu command line switch,
just "qemu-system-x86_64 dos.cow"
and run the executable inside the emulated dos environment.
Any comment will be appreciated. Thanks in advance.
Which (virtual) hardware disk controller and (if applicable)
mainboard
chipset does this assume?
Is this the hardware emulated by default by the qemu command you
ran?
Are you trying to access the ISA-bus compatible DMA controller at
I/O
port 0x0040 using the obscure fact that older ISA machines only
decoded the low 10 bits of the I/O port address?
========== code attached below ===========
.386
STACK segment para stack 'STACK'
db 512 dup(0)
STACK ends
BMCR_BASE equ 0c040h ; Bus Master Control
Register base address
BM_COMMAND_REG equ BMCR_BASE ; Command
BM_STATUS_REG equ BMCR_BASE + 2 ; Status
BM_PRD_ADDR_REG equ BMCR_BASE + 4 ; Physical Region
Descriptor address
PIO_BASE_ADDR1 equ 01f0h
PIO_BASE_ADDR2 equ 03f6h
SEC_NUM equ 1
LBASECTOR equ 0
DATA segment use16 para 'DATA'
align 2
Buf db 512 * SEC_NUM DUP (0) ; DMA Buffer
BufLen equ $ - Buf
align 4
PRD_Buf dd 0 ; Physical Region Descriptor
Buffer
dd 0
DATA ends
EchoCH macro ascii
mov ah, 2
mov dl, ascii
int 21h
endm
outx macro reg, val
mov dx, reg
mov al, val
out dx, al
endm
inx macro reg
mov dx, reg
in al, dx
endm
CODE segment use16
assume cs:CODE,ds:DATA,ss:STACK
start:
mov ax, DATA
mov ds, ax
cli
outx BM_COMMAND_REG, 00h ; start/STOP = 0, reset BM
status
outx BM_STATUS_REG, 00000110B; clear interrupt and
error flag
; create PRD
mov ax, ds
movzx eax, ax
shl eax, 4 ; eax=base for data
segment
add eax, offset Buf ; eax=base for PRD_Bufj
mov PRD_Buf, eax ; Physical address
mov word ptr [PRD_Buf+4], BufLen ; Byte count [15:1]
mov word ptr [PRD_Buf+6], 8000h ; EOT=1
mov ax, ds
movzx eax, ax
shl eax, 4
add eax, offset PRD_Buf
mov dx, BM_PRD_ADDR_REG
out dx, eax ; PRD address
outx BM_COMMAND_REG, 08h ; R/W=1, read from disk
call WaitDevice
outx PIO_BASE_ADDR1+6, 00h ; Dev=0
call WaitDevice
;outx PIO_BASE_ADDR2, 00 ; enable interrupt
outx PIO_BASE_ADDR1 + 1, 00h ; =00
outx PIO_BASE_ADDR1 + 2, SEC_NUM ; sector num
outx PIO_BASE_ADDR1 + 3, LBASECTOR
outx PIO_BASE_ADDR1 + 4, LBASECTOR/256
outx PIO_BASE_ADDR1 + 5, LBASECTOR/65536
outx PIO_BASE_ADDR1 + 6, 01000000B OR
(LBASECTOR/256/256/256)
outx PIO_BASE_ADDR1 + 7, 0C8h ; 0C8h=READ
DMA
outx BM_COMMAND_REG, 09h ; R/W=1, START/STOP=1,
start DMA
@@:
inx BM_STATUS_REG
and al, 00000100B
JZ @B
outx BM_STATUS_REG, 00000100B
outx BM_COMMAND_REG, 00h ; START/STOP = 0, stop DMA
sti
call ShowBuf
mov ax,4C00h
int 21h
; Wait until BSY=0,DRQ=0
WaitDevice proc
@@:
inx PIO_BASE_ADDR1 + 7
and al, 10001000b
jnz @B
ret
WaitDevice endp
;Show what's in the buffer
ShowBuf proc
lea si, Buf
cld
mov bp, BufLen / 16
NextLine:
mov cx,16
NextCh:
lodsb
push ax
shr al, 4
call ToAscii
EchoCH al
pop ax
call ToAscii
EchoCH al
EchoCH ' '
loop NextCh
EchoCH 0dh
EchoCH 0ah
dec bp
jnz NextLine
ret
ShowBuf endp
ToAscii proc
and al, 0fh
cmp al, 10
jae @F
add al,'0'
ret
@@: add al,'A' - 10
ret
ToAscii endp
CODE ends
end start
Enjoy
Jakob
--
Jakob Bohm, CIO, Partner, WiseMo A/S. https://www.wisemo.com
Transformervej 29, 2860 Søborg, Denmark. Direct +45 31 13 16 10
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