/* Pilote pour le controleur DMA Intel 8237A */
/* Copyright (C) 2008  Emmanuel Varoquaux

   This file is part of XOS.

   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 3 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.

   You should have received a copy of the GNU General Public License
   along with this program.  If not, see <http://www.gnu.org/licenses/>. */

/* Le pilote est actuellement limite aux canaux 0 a 3. Il serait facile de
 * l'etendre aux canaux 4 a 7. */

#include <panic.h>
#include <asm.h>

/* registres du controleur */
static const unsigned short address_port[] = {0x0, 0x2, 0x4, 0x6};
static const unsigned short word_count_port[] = {0x1, 0x3, 0x5, 0x7};
static const unsigned short page_port[] = {0, 0x83, 0x81, 0x82};

static inline void disable_channel(unsigned char channel)
{
  outbp(0x04 | channel, 0xa);
}

static inline void enable_channel(unsigned char channel)
{
  outbp(channel, 0xa);
}

static inline void reset()
{
  outbp(0, 0xc);                        /* clear the flip-flop */
}

static inline void set_mode(unsigned char channel, unsigned char transfer_type)
{
  outbp(0x40 | (transfer_type << 2) | channel, 0xb); /* disable auto-initialization, address decrement, single mode */
}

static inline void set_address(unsigned char channel, unsigned long address)
{
  register unsigned short port;

  if (channel != 0)
    outbp(address >> 16, page_port[channel]);/* page (bits 16-19) */
  port = address_port[channel];
  outbp(address, port);                 /* bits 0-7 */
  outbp(address >> 8, port);            /* bits 8-15 */
}

static inline void set_word_count(unsigned char channel, unsigned short word_count)
{
  register unsigned short port;

  port = word_count_port[channel];
  outbp(word_count, port);              /* 8 bits de poids faible */
  outbp(word_count >> 8, port);         /* 8 bits de poids fort */
}

static void setup_dma(unsigned char channel, unsigned char transfer_type, unsigned long address, unsigned int count)
{
  cli();
  disable_channel(channel);             /* on masque le canal */
  reset();                              /* reset */
  set_mode(channel, transfer_type);     /* commande */
  set_address(channel, address);        /* adresse */
  set_word_count(channel, count - 1);   /* nombre de transferts */
  enable_channel(channel);              /* on active le canal */
  sti();
}

/* address et count doivent etre tels que :
 * - count doit etre inferieur ou egal a 64K
 * - la zone memoire ne doit pas traverser une frontiere de page (64K). */
void dma_setup(unsigned char channel, unsigned char transfer_type, unsigned long address, unsigned int count)
{
  if (address > 0x100000)
    panic("DMA: region must be in the first 1MB of memory");
  if (count > 0x10000)
    panic("DMA: cannot transfer more than 64K");
  if ((address + count) >> 16 != address >> 16)
    panic("DMA: region crosses a physical alignment boundary");
  setup_dma(channel, transfer_type, address, count);
}