bouncebuf.c

/*
 * Generic bounce buffer implementation
 *
 * Copyright (C) 2012 Marek Vasut <marex@denx.de>
 *
 * See file CREDITS for list of people who contributed to this
 * project.
 *
 * 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 2 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, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston,
 * MA 02111-1307 USA
 */

#include <common.h>
#include <malloc.h>
#include <errno.h>
#include <bouncebuf.h>

static int addr_aligned(struct bounce_buffer *state)
{
	const ulong align_mask = ARCH_DMA_MINALIGN - 1;

	/* Check if start is aligned */
	if ((ulong)state->user_buffer & align_mask) {
		debug("Unaligned buffer address %p\n", state->user_buffer);
		return 0;
	}

	/* Check if length is aligned */
	if (state->len != state->len_aligned) {
		debug("Unaligned buffer length %d\n", state->len);
		return 0;
	}

	/* Aligned */
	return 1;
}

int bounce_buffer_start(struct bounce_buffer *state, void *data,
			size_t len, unsigned int flags)
{
	state->user_buffer = data;
	state->bounce_buffer = data;
	state->len = len;
	state->len_aligned = roundup(len, ARCH_DMA_MINALIGN);
	state->flags = flags;

	if (!addr_aligned(state)) {
		state->bounce_buffer = memalign(ARCH_DMA_MINALIGN,
						state->len_aligned);
		if (!state->bounce_buffer)
			return -ENOMEM;

		if (state->flags & GEN_BB_READ)
			memcpy(state->bounce_buffer, state->user_buffer,
				state->len);
	}

	/*
	 * Flush data to RAM so DMA reads can pick it up,
	 * and any CPU writebacks don't race with DMA writes
	 */
	flush_dcache_range((unsigned long)state->bounce_buffer,
				(unsigned long)(state->bounce_buffer) +
					state->len_aligned);

	return 0;
}

int bounce_buffer_stop(struct bounce_buffer *state)
{
	if (state->flags & GEN_BB_WRITE) {
		/* Invalidate cache so that CPU can see any newly DMA'd data */
		invalidate_dcache_range((unsigned long)state->bounce_buffer,
					(unsigned long)(state->bounce_buffer) +
						state->len_aligned);
	}

	if (state->bounce_buffer == state->user_buffer)
		return 0;

	if (state->flags & GEN_BB_WRITE)
		memcpy(state->user_buffer, state->bounce_buffer, state->len);

	free(state->bounce_buffer);

	return 0;
}