source: xtideuniversalbios/trunk/XTIDE_Universal_BIOS/Src/Device/IDE/IdeDmaBlock.asm@ 481

; Project name  :   XTIDE Universal BIOS
; Description   :   IDE Read/Write functions for transferring
;                   block using DMA.
;                   These functions should only be called from IdeTransfer.asm.

;
; XTIDE Universal BIOS and Associated Tools
; Copyright (C) 2009-2010 by Tomi Tilli, 2011-2012 by XTIDE Universal BIOS Team.
;
; This program is free software; you can redistribute it and/or modify
; it under the terms of the GNU General Public License as published by
; the Free Software Foundation; either version 2 of the License, or
; (at your option) any later version.
;
; This program is distributed in the hope that it will be useful,
; but WITHOUT ANY WARRANTY; without even the implied warranty of
; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
; GNU General Public License for more details.
; Visit http://www.gnu.org/licenses/old-licenses/gpl-2.0.html
;


; Section containing code
SECTION .text

;--------------------------------------------------------------------
; IdeDmaBlock_WriteToXTCF
;   Parameters:
;       CX:     Block size in 512 byte sectors
;       DX:     XTCF Base Port Address
;       ES:SI:  Physical address to buffer to receive data
;   Returns:
;       Nothing
;   Corrupts registers:
;       AX, BX, CX, DX
;--------------------------------------------------------------------
ALIGN JUMP_ALIGN
IdeDmaBlock_WriteToXTCF:
    xchg    si, di
    mov     bl, CHANNEL_3 | READ | AUTOINIT_DISABLE | ADDRESS_INCREMENT | DEMAND_MODE
    call    TransferBlockToOrFromXTCF
    xchg    di, si
    ret


;--------------------------------------------------------------------
; IdeDmaBlock_ReadFromXTCF
;   Parameters:
;       CX:     Block size in 512 byte sectors
;       DX:     XTCF Base Port Address
;       ES:DI:  Physical address to buffer to receive data
;   Returns:
;       Nothing
;   Corrupts registers:
;       AX, BX, CX, DX
;--------------------------------------------------------------------
ALIGN JUMP_ALIGN
IdeDmaBlock_ReadFromXTCF:
    mov     bl, CHANNEL_3 | WRITE | AUTOINIT_DISABLE | ADDRESS_INCREMENT | DEMAND_MODE
    ; Fall to TransferBlockToOrFromXTCF


;--------------------------------------------------------------------
; TransferBlockToOrFromXTCF
;   Parameters:
;       BL:     Mode byte for DMA Mode Register
;       CX:     Block size in 512 byte sectors
;       DX:     XTCF Base Port Address
;       ES:DI:  Physical address to buffer to receive data
;   Returns:
;       Nothing
;   Corrupts registers:
;       AX, BX, CX, DX
;--------------------------------------------------------------------
TransferBlockToOrFromXTCF:
    ; 8-bit DMA transfers must be done withing 64k physical page.
    ; We support maximum of 128 sectors (65536 bytes) per one INT 13h call
    ; so we might need to separate transfer to 2 separate DMA operations.

    ; Load XT-CF Control Register port to DX
    add     dl, XTCF_CONTROL_REGISTER

    ; Calculate bytes for first page
    mov     ax, di
    neg     ax                                      ; AX = Max BYTEs for first page
%ifdef USE_186
    shl     cx, 9                                   ; CX = Block size in BYTEs
%else
    xchg    cl, ch
    shl     cx, 1
%endif
    cmp     cx, ax
    jbe     SHORT .TransferLastDmaPageWithSizeInCX

    ; Push size for second DMA page
    xchg    cx, ax                                  ; CX = BYTEs for first page
    sub     ax, cx                                  ; AX = BYTEs for second page
    push    ax

    ; Transfer first DMA page
    call    StartDMAtransferForXTCFwithDmaModeInBL
    pop     cx                                      ; Pop size for second DMA page

.TransferLastDmaPageWithSizeInCX:
    ; Fall to StartDMAtransferForXTCFwithDmaModeInBL


;--------------------------------------------------------------------
; StartDMAtransferForXTCFwithDmaModeInBL
;   Parameters:
;       CX:     Number of BYTEs to transfer
;       BL:     Byte for DMA Mode Register
;       DX:     XTCF Control Register
;   Returns:
;       Nothing
;   Corrupts registers:
;       AX
;--------------------------------------------------------------------
ALIGN JUMP_ALIGN
StartDMAtransferForXTCFwithDmaModeInBL:
    ; Program 8-bit DMA Controller
    ; Disable Interrupts and DMA Channel 3 during DMA setup
    mov     al, SET_CH3_MASK_BIT
    cli                                     ; Disable interrupts
    out     MASK_REGISTER_DMA8_out, al      ; Disable DMA Channel 3

    ; Set DMA Mode (read or write using channel 3)
    mov     al, bl
    out     MODE_REGISTER_DMA8_out, al

    ; Set address to DMA controller
    out     CLEAR_FLIPFLOP_DMA8_out, al     ; Reset flip-flop to low byte
    mov     ax, es
    out     PAGE_DMA8_CH_3, al
    mov     ax, di
    out     BASE_AND_CURRENT_ADDRESS_REGISTER_DMA8_CH3_out, al  ; Low byte
    mov     al, ah
    out     BASE_AND_CURRENT_ADDRESS_REGISTER_DMA8_CH3_out, al  ; High byte

    ; Set number of bytes to transfer (DMA controller must be programmed number of bytes - 1)
    mov     ax, cx
    dec     ax                              ; DMA controller is programmed for one byte less
    out     BASE_AND_CURRENT_COUNT_REGISTER_DMA8_CH3_out, al    ; Low byte
    mov     al, ah
    out     BASE_AND_CURRENT_COUNT_REGISTER_DMA8_CH3_out, al    ; High byte

    ; Enable DMA Channel 3
    mov     al, CLEAR_CH3_MASK_BIT
    out     MASK_REGISTER_DMA8_out, al      ; Enable DMA Channel 3
    sti                                     ; Enable interrupts


    ; XT-CF transfers 16 bytes at a time. We need to manually
    ; start transfer for every block.
ALIGN JUMP_ALIGN
.TransferNextBlock:
    mov     al, RAISE_DRQ_AND_CLEAR_XTCF_XFER_COUNTER
    cli                                 ; We want no ISR to read DMA Status Register before we do
    out     dx, al                      ; Transfer up to 16 bytes to/from XT-CF card
    ; * Here XT-CF sets CPU to wait states during transfer *
    in      al, STATUS_REGISTER_DMA8_in
    sti
    test    al, FLG_CH3_HAS_REACHED_TERMINAL_COUNT
    jz      SHORT .TransferNextBlock    ; All bytes transferred?

    ; Restore XT-CF to normal operation
    mov     al, XTCF_DMA_MODE
    out     dx, al

    ; Increment physical address in ES:DI
    mov     ax, es
    add     di, cx
    adc     al, ah
    mov     es, ax
    ret