100 lines
2.3 KiB
C
100 lines
2.3 KiB
C
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// SPDX-License-Identifier: GPL-2.0-or-later
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/*
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* ISA DMA support functions
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* Copyright (c) by Jaroslav Kysela <perex@perex.cz>
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*/
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/*
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* Defining following add some delay. Maybe this helps for some broken
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* ISA DMA controllers.
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*/
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#undef HAVE_REALLY_SLOW_DMA_CONTROLLER
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#include <linux/export.h>
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#include <sound/core.h>
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#include <asm/dma.h>
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/**
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* snd_dma_program - program an ISA DMA transfer
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* @dma: the dma number
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* @addr: the physical address of the buffer
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* @size: the DMA transfer size
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* @mode: the DMA transfer mode, DMA_MODE_XXX
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*
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* Programs an ISA DMA transfer for the given buffer.
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*/
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void snd_dma_program(unsigned long dma,
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unsigned long addr, unsigned int size,
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unsigned short mode)
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{
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unsigned long flags;
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flags = claim_dma_lock();
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disable_dma(dma);
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clear_dma_ff(dma);
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set_dma_mode(dma, mode);
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set_dma_addr(dma, addr);
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set_dma_count(dma, size);
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if (!(mode & DMA_MODE_NO_ENABLE))
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enable_dma(dma);
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release_dma_lock(flags);
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}
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EXPORT_SYMBOL(snd_dma_program);
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/**
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* snd_dma_disable - stop the ISA DMA transfer
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* @dma: the dma number
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*
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* Stops the ISA DMA transfer.
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*/
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void snd_dma_disable(unsigned long dma)
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{
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unsigned long flags;
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flags = claim_dma_lock();
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clear_dma_ff(dma);
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disable_dma(dma);
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release_dma_lock(flags);
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}
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EXPORT_SYMBOL(snd_dma_disable);
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/**
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* snd_dma_pointer - return the current pointer to DMA transfer buffer in bytes
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* @dma: the dma number
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* @size: the dma transfer size
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*
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* Return: The current pointer in DMA transfer buffer in bytes.
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*/
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unsigned int snd_dma_pointer(unsigned long dma, unsigned int size)
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{
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unsigned long flags;
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unsigned int result, result1;
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flags = claim_dma_lock();
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clear_dma_ff(dma);
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if (!isa_dma_bridge_buggy)
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disable_dma(dma);
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result = get_dma_residue(dma);
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/*
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* HACK - read the counter again and choose higher value in order to
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* avoid reading during counter lower byte roll over if the
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* isa_dma_bridge_buggy is set.
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*/
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result1 = get_dma_residue(dma);
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if (!isa_dma_bridge_buggy)
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enable_dma(dma);
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release_dma_lock(flags);
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if (unlikely(result < result1))
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result = result1;
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#ifdef CONFIG_SND_DEBUG
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if (result > size)
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pr_err("ALSA: pointer (0x%x) for DMA #%ld is greater than transfer size (0x%x)\n", result, dma, size);
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#endif
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if (result >= size || result == 0)
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return 0;
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else
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return size - result;
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}
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EXPORT_SYMBOL(snd_dma_pointer);
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