sound/core/isadma.c

// SPDX-License-Identifier: GPL-2.0-or-later
/*
 *  ISA DMA support functions
 *  Copyright (c) by Jaroslav Kysela <perex@perex.cz>
 */

/*
 * Defining following add some delay. Maybe this helps for some broken
 * ISA DMA controllers.
 */

#undef HAVE_REALLY_SLOW_DMA_CONTROLLER

#include <linux/export.h>
#include <sound/core.h>
#include <asm/dma.h>

/**
 * snd_dma_program - program an ISA DMA transfer
 * @dma: the dma number
 * @addr: the physical address of the buffer
 * @size: the DMA transfer size
 * @mode: the DMA transfer mode, DMA_MODE_XXX
 *
 * Programs an ISA DMA transfer for the given buffer.
 */
void snd_dma_program(unsigned long dma,
		     unsigned long addr, unsigned int size,
                     unsigned short mode)
{
	unsigned long flags;

	flags = claim_dma_lock();
	disable_dma(dma);
	clear_dma_ff(dma);
	set_dma_mode(dma, mode);
	set_dma_addr(dma, addr);
	set_dma_count(dma, size);
	if (!(mode & DMA_MODE_NO_ENABLE))
		enable_dma(dma);
	release_dma_lock(flags);
}
EXPORT_SYMBOL(snd_dma_program);

/**
 * snd_dma_disable - stop the ISA DMA transfer
 * @dma: the dma number
 *
 * Stops the ISA DMA transfer.
 */
void snd_dma_disable(unsigned long dma)
{
	unsigned long flags;

	flags = claim_dma_lock();
	clear_dma_ff(dma);
	disable_dma(dma);
	release_dma_lock(flags);
}
EXPORT_SYMBOL(snd_dma_disable);

/**
 * snd_dma_pointer - return the current pointer to DMA transfer buffer in bytes
 * @dma: the dma number
 * @size: the dma transfer size
 *
 * Return: The current pointer in DMA transfer buffer in bytes.
 */
unsigned int snd_dma_pointer(unsigned long dma, unsigned int size)
{
	unsigned long flags;
	unsigned int result, result1;

	flags = claim_dma_lock();
	clear_dma_ff(dma);
	if (!isa_dma_bridge_buggy)
		disable_dma(dma);
	result = get_dma_residue(dma);
	/*
	 * HACK - read the counter again and choose higher value in order to
	 * avoid reading during counter lower byte roll over if the
	 * isa_dma_bridge_buggy is set.
	 */
	result1 = get_dma_residue(dma);
	if (!isa_dma_bridge_buggy)
		enable_dma(dma);
	release_dma_lock(flags);
	if (unlikely(result < result1))
		result = result1;
#ifdef CONFIG_SND_DEBUG
	if (result > size)
		pr_err("ALSA: pointer (0x%x) for DMA #%ld is greater than transfer size (0x%x)\n", result, dma, size);
#endif
	if (result >= size || result == 0)
		return 0;
	else
		return size - result;
}
EXPORT_SYMBOL(snd_dma_pointer);