MMC: Implement generic bounce buffer

This implements generic bounce buffer at the end of MMC command submission
chain. Therefore if unaligned data are passed, they are copied. This stuff
should be pushed down into the MMC subsystem to squash all places generating
these unaligned data.

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

drivers/mmc/mmc.c

@@ -47,10 +47,105 @@ int __board_mmc_getcd(struct mmc *mmc) {
 int board_mmc_getcd(struct mmc *mmc)__attribute__((weak,
 	alias("__board_mmc_getcd")));
 
+#ifdef CONFIG_MMC_BOUNCE_BUFFER
+static int mmc_bounce_need_bounce(struct mmc_data *orig)
+{
+	ulong addr, len;
+
+	if (orig->flags & MMC_DATA_READ)
+		addr = (ulong)orig->dest;
+	else
+		addr = (ulong)orig->src;
+
+	if (addr % ARCH_DMA_MINALIGN) {
+		debug("MMC: Unaligned data destination address %08lx!\n", addr);
+		return 1;
+	}
+
+	len = (ulong)(orig->blocksize * orig->blocks);
+	if (len % ARCH_DMA_MINALIGN) {
+		debug("MMC: Unaligned data destination length %08lx!\n", len);
+		return 1;
+	}
+
+	return 0;
+}
+
+static int mmc_bounce_buffer_start(struct mmc_data *backup,
+					struct mmc_data *orig)
+{
+	ulong origlen, len;
+	void *buffer;
+
+	if (!orig)
+		return 0;
+
+	if (!mmc_bounce_need_bounce(orig))
+		return 0;
+
+	memcpy(backup, orig, sizeof(struct mmc_data));
+
+	origlen = orig->blocksize * orig->blocks;
+	len = roundup(origlen, ARCH_DMA_MINALIGN);
+	buffer = memalign(ARCH_DMA_MINALIGN, len);
+	if (!buffer) {
+		puts("MMC: Error allocating MMC bounce buffer!\n");
+		return 1;
+	}
+
+	if (orig->flags & MMC_DATA_READ) {
+		orig->dest = buffer;
+	} else {
+		memcpy(buffer, orig->src, origlen);
+		orig->src = buffer;
+	}
+
+	return 0;
+}
+
+static void mmc_bounce_buffer_stop(struct mmc_data *backup,
+					struct mmc_data *orig)
+{
+	ulong len;
+
+	if (!orig)
+		return;
+
+	if (!mmc_bounce_need_bounce(backup))
+		return;
+
+	if (backup->flags & MMC_DATA_READ) {
+		len = backup->blocksize * backup->blocks;
+		memcpy(backup->dest, orig->dest, len);
+		free(orig->dest);
+		orig->dest = backup->dest;
+	} else {
+		free((void *)orig->src);
+		orig->src = backup->src;
+	}
+
+	return;
+
+}
+#else
+static inline int mmc_bounce_buffer_start(struct mmc_data *backup,
+					struct mmc_data *orig) { }
+static inline void mmc_bounce_buffer_stop(struct mmc_data *backup,
+					struct mmc_data *orig) { }
+#endif
+
 int mmc_send_cmd(struct mmc *mmc, struct mmc_cmd *cmd, struct mmc_data *data)
 {
-#ifdef CONFIG_MMC_TRACE
+	struct mmc_data backup;
 	int ret;
+
+	memset(&backup, 0, sizeof(backup));
+
+	ret = mmc_bounce_buffer_start(&backup, data);
+	if (ret)
+		return ret;
+
+#ifdef CONFIG_MMC_TRACE
 	int i;
 	u8 *ptr;
 
@@ -99,10 +194,11 @@ int mmc_send_cmd(struct mmc *mmc, struct mmc_cmd *cmd, struct mmc_data *data)
 			printf("\t\tERROR MMC rsp not supported\n");
 			break;
 	}
-	return ret;
 #else
-	return mmc->send_cmd(mmc, cmd, data);
+	ret = mmc->send_cmd(mmc, cmd, data);
 #endif
+	mmc_bounce_buffer_stop(&backup, data);
+	return ret;
 }
 
 int mmc_send_status(struct mmc *mmc, int timeout)