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  */
  42 void 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 }
  58 EXPORT_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  */
  66 void 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 }
  75 EXPORT_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  */
  84 unsigned 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 }
 114 EXPORT_SYMBOL(snd_dma_pointer);