LXR linux/sound/core/isadma.c

   1/*
   2 *  ISA DMA support functions
   3 *  Copyright (c) by Jaroslav Kysela <perex@perex.cz>
   4 *
   5 *
   6 *   This program is free software; you can redistribute it and/or modify
   7 *   it under the terms of the GNU General Public License as published by
   8 *   the Free Software Foundation; either version 2 of the License, or
   9 *   (at your option) any later version.
  10 *
  11 *   This program is distributed in the hope that it will be useful,
  12 *   but WITHOUT ANY WARRANTY; without even the implied warranty of
  13 *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14 *   GNU General Public License for more details.
  15 *
  16 *   You should have received a copy of the GNU General Public License
  17 *   along with this program; if not, write to the Free Software
  18 *   Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307 USA
  19 *
  20 */
  21
  22/*
  23 * Defining following add some delay. Maybe this helps for some broken
  24 * ISA DMA controllers.
  25 */
  26
  27#undef HAVE_REALLY_SLOW_DMA_CONTROLLER
  28
  29#include <linux/export.h>
  30#include <sound/core.h>
  31#include <asm/dma.h>
  32
  33/**
  34 * snd_dma_program - program an ISA DMA transfer
  35 * @dma: the dma number
  36 * @addr: the physical address of the buffer
  37 * @size: the DMA transfer size
  38 * @mode: the DMA transfer mode, DMA_MODE_XXX
  39 *
  40 * Programs an ISA DMA transfer for the given buffer.
  41 */
  42void snd_dma_program(unsigned long dma,
  43                     unsigned long addr, unsigned int size,
  44                     unsigned short mode)
  45{
  46        unsigned long flags;
  47
  48        flags = claim_dma_lock();
  49        disable_dma(dma);
  50        clear_dma_ff(dma);
  51        set_dma_mode(dma, mode);
  52        set_dma_addr(dma, addr);
  53        set_dma_count(dma, size);
  54        if (!(mode & DMA_MODE_NO_ENABLE))
  55                enable_dma(dma);
  56        release_dma_lock(flags);
  57}
  58EXPORT_SYMBOL(snd_dma_program);
  59
  60/**
  61 * snd_dma_disable - stop the ISA DMA transfer
  62 * @dma: the dma number
  63 *
  64 * Stops the ISA DMA transfer.
  65 */
  66void snd_dma_disable(unsigned long dma)
  67{
  68        unsigned long flags;
  69
  70        flags = claim_dma_lock();
  71        clear_dma_ff(dma);
  72        disable_dma(dma);
  73        release_dma_lock(flags);
  74}
  75EXPORT_SYMBOL(snd_dma_disable);
  76
  77/**
  78 * snd_dma_pointer - return the current pointer to DMA transfer buffer in bytes
  79 * @dma: the dma number
  80 * @size: the dma transfer size
  81 *
  82 * Return: The current pointer in DMA transfer buffer in bytes.
  83 */
  84unsigned int snd_dma_pointer(unsigned long dma, unsigned int size)
  85{
  86        unsigned long flags;
  87        unsigned int result, result1;
  88
  89        flags = claim_dma_lock();
  90        clear_dma_ff(dma);
  91        if (!isa_dma_bridge_buggy)
  92                disable_dma(dma);
  93        result = get_dma_residue(dma);
  94        /*
  95         * HACK - read the counter again and choose higher value in order to
  96         * avoid reading during counter lower byte roll over if the
  97         * isa_dma_bridge_buggy is set.
  98         */
  99        result1 = get_dma_residue(dma);
 100        if (!isa_dma_bridge_buggy)
 101                enable_dma(dma);
 102        release_dma_lock(flags);
 103        if (unlikely(result < result1))
 104                result = result1;
 105#ifdef CONFIG_SND_DEBUG
 106        if (result > size)
 107                pr_err("ALSA: pointer (0x%x) for DMA #%ld is greater than transfer size (0x%x)\n", result, dma, size);
 108#endif
 109        if (result >= size || result == 0)
 110                return 0;
 111        else
 112                return size - result;
 113}
 114EXPORT_SYMBOL(snd_dma_pointer);
 115