COMMON: Implement common bounce buffer

Implement common bounce buffer to be used on a less capable hardware.
That includes hardware that can not do DMA from any address or such.

Signed-off-by: Marek Vasut <marex@denx.de>
Cc: Fabio Estevam <festevam@gmail.com>
Cc: Andy Fleming <afleming@freescale.com>
Signed-off-by: Andy Fleming <afleming@freescale.com>

common/bouncebuf.c

@@ -0,0 +1,92 @@
+/*
+ * 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(void *data, size_t len)
+{
+	const ulong align_mask = ARCH_DMA_MINALIGN - 1;
+
+	/* Check if start is aligned */
+	if ((ulong)data & align_mask) {
+		debug("Unaligned start address %p\n", data);
+		return 0;
+	}
+
+	data += len;
+
+	/* Check if end is aligned */
+	if ((ulong)data & align_mask) {
+		debug("Unaligned end address %p\n", data);
+		return 0;
+	}
+
+	/* Aligned */
+	return 1;
+}
+
+int bounce_buffer_start(void **data, size_t len, void **backup, uint8_t flags)
+{
+	void *tmp;
+	size_t alen;
+
+	if (addr_aligned(*data, len)) {
+		*backup = NULL;
+		return 0;
+	}
+
+	alen = roundup(len, ARCH_DMA_MINALIGN);
+	tmp = memalign(ARCH_DMA_MINALIGN, alen);
+
+	if (!tmp)
+		return -ENOMEM;
+
+	if (flags & GEN_BB_READ)
+		memcpy(tmp, *data, len);
+
+	*backup = *data;
+	*data = tmp;
+
+	return 0;
+}
+
+int bounce_buffer_stop(void **data, size_t len, void **backup, uint8_t flags)
+{
+	void *tmp = *data;
+
+	/* The buffer was already aligned, since "backup" is NULL. */
+	if (!*backup)
+		return 0;
+
+	if (flags & GEN_BB_WRITE)
+		memcpy(*backup, *data, len);
+
+	*data = *backup;
+	free(tmp);
+
+	return 0;
+}