mtd: atmel_nand: Add DMA support to access Nandflash

Some SAM9 chips have the ability to perform DMA between CPU and SMC controller.
This patch adds DMA support for SAM9RL, SAM9G45, SSAM9G46,AM9M10, SAM9M11.

Signed-off-by: Hong Xu <[e-mail]>
Tested-by: Ryan Mallon <[e-mail]>
Acked-by: Ryan Mallon <[e-mail]>
Signed-off-by: David Woodhouse <[e-mail]>

drivers/mtd/nand/atmel_nand.c

···
 #define no_ecc		0
 #endif
 
+static int use_dma = 1;
+module_param(use_dma, int, 0);
+
 static int on_flash_bbt = 0;
 module_param(on_flash_bbt, int, 0);
 
···
 	struct nand_chip	nand_chip;
 	struct mtd_info		mtd;
 	void __iomem		*io_base;
+	dma_addr_t		io_phys;
 	struct atmel_nand_data	*board;
 	struct device		*dev;
 	void __iomem		*ecc;
+
+	struct completion	comp;
+	struct dma_chan		*dma_chan;
 };
+
+static int cpu_has_dma(void)
+{
+	return cpu_is_at91sam9rl() || cpu_is_at91sam9g45();
+}
 
 /*
  * Enable NAND.
···
 /*
  * Minimal-overhead PIO for data access.
  */
-static void atmel_read_buf(struct mtd_info *mtd, u8 *buf, int len)
+static void atmel_read_buf8(struct mtd_info *mtd, u8 *buf, int len)
 {
 	struct nand_chip	*nand_chip = mtd->priv;
 
···
 	__raw_readsw(nand_chip->IO_ADDR_R, buf, len / 2);
 }
 
-static void atmel_write_buf(struct mtd_info *mtd, const u8 *buf, int len)
+static void atmel_write_buf8(struct mtd_info *mtd, const u8 *buf, int len)
 {
 	struct nand_chip	*nand_chip = mtd->priv;
 
···
 	struct nand_chip	*nand_chip = mtd->priv;
 
 	__raw_writesw(nand_chip->IO_ADDR_W, buf, len / 2);
+}
+
+static void dma_complete_func(void *completion)
+{
+	complete(completion);
+}
+
+static int atmel_nand_dma_op(struct mtd_info *mtd, void *buf, int len,
+			       int is_read)
+{
+	struct dma_device *dma_dev;
+	enum dma_ctrl_flags flags;
+	dma_addr_t dma_src_addr, dma_dst_addr, phys_addr;
+	struct dma_async_tx_descriptor *tx = NULL;
+	dma_cookie_t cookie;
+	struct nand_chip *chip = mtd->priv;
+	struct atmel_nand_host *host = chip->priv;
+	void *p = buf;
+	int err = -EIO;
+	enum dma_data_direction dir = is_read ? DMA_FROM_DEVICE : DMA_TO_DEVICE;
+
+	if (buf >= high_memory) {
+		struct page *pg;
+
+		if (((size_t)buf & PAGE_MASK) !=
+		    ((size_t)(buf + len - 1) & PAGE_MASK)) {
+			dev_warn(host->dev, "Buffer not fit in one page\n");
+			goto err_buf;
+		}
+
+		pg = vmalloc_to_page(buf);
+		if (pg == 0) {
+			dev_err(host->dev, "Failed to vmalloc_to_page\n");
+			goto err_buf;
+		}
+		p = page_address(pg) + ((size_t)buf & ~PAGE_MASK);
+	}
+
+	dma_dev = host->dma_chan->device;
+
+	flags = DMA_CTRL_ACK | DMA_PREP_INTERRUPT | DMA_COMPL_SKIP_SRC_UNMAP |
+		DMA_COMPL_SKIP_DEST_UNMAP;
+
+	phys_addr = dma_map_single(dma_dev->dev, p, len, dir);
+	if (dma_mapping_error(dma_dev->dev, phys_addr)) {
+		dev_err(host->dev, "Failed to dma_map_single\n");
+		goto err_buf;
+	}
+
+	if (is_read) {
+		dma_src_addr = host->io_phys;
+		dma_dst_addr = phys_addr;
+	} else {
+		dma_src_addr = phys_addr;
+		dma_dst_addr = host->io_phys;
+	}
+
+	tx = dma_dev->device_prep_dma_memcpy(host->dma_chan, dma_dst_addr,
+					     dma_src_addr, len, flags);
+	if (!tx) {
+		dev_err(host->dev, "Failed to prepare DMA memcpy\n");
+		goto err_dma;
+	}
+
+	init_completion(&host->comp);
+	tx->callback = dma_complete_func;
+	tx->callback_param = &host->comp;
+
+	cookie = tx->tx_submit(tx);
+	if (dma_submit_error(cookie)) {
+		dev_err(host->dev, "Failed to do DMA tx_submit\n");
+		goto err_dma;
+	}
+
+	dma_async_issue_pending(host->dma_chan);
+	wait_for_completion(&host->comp);
+
+	err = 0;
+
+err_dma:
+	dma_unmap_single(dma_dev->dev, phys_addr, len, dir);
+err_buf:
+	if (err != 0)
+		dev_warn(host->dev, "Fall back to CPU I/O\n");
+	return err;
+}
+
+static void atmel_read_buf(struct mtd_info *mtd, u8 *buf, int len)
+{
+	struct nand_chip *chip = mtd->priv;
+	struct atmel_nand_host *host = chip->priv;
+
+	if (use_dma && len >= mtd->oobsize)
+		if (atmel_nand_dma_op(mtd, buf, len, 1) == 0)
+			return;
+
+	if (host->board->bus_width_16)
+		atmel_read_buf16(mtd, buf, len);
+	else
+		atmel_read_buf8(mtd, buf, len);
+}
+
+static void atmel_write_buf(struct mtd_info *mtd, const u8 *buf, int len)
+{
+	struct nand_chip *chip = mtd->priv;
+	struct atmel_nand_host *host = chip->priv;
+
+	if (use_dma && len >= mtd->oobsize)
+		if (atmel_nand_dma_op(mtd, (void *)buf, len, 0) == 0)
+			return;
+
+	if (host->board->bus_width_16)
+		atmel_write_buf16(mtd, buf, len);
+	else
+		atmel_write_buf8(mtd, buf, len);
 }
 
 /*
···
 		return -ENOMEM;
 	}
 
+	host->io_phys = (dma_addr_t)mem->start;
+
 	host->io_base = ioremap(mem->start, mem->end - mem->start + 1);
 	if (host->io_base == NULL) {
 		printk(KERN_ERR "atmel_nand: ioremap failed\n");
···
 
 	nand_chip->chip_delay = 20;		/* 20us command delay time */
 
-	if (host->board->bus_width_16) {	/* 16-bit bus width */
+	if (host->board->bus_width_16)	/* 16-bit bus width */
 		nand_chip->options |= NAND_BUSWIDTH_16;
-		nand_chip->read_buf = atmel_read_buf16;
-		nand_chip->write_buf = atmel_write_buf16;
-	} else {
-		nand_chip->read_buf = atmel_read_buf;
-		nand_chip->write_buf = atmel_write_buf;
-	}
+
+	nand_chip->read_buf = atmel_read_buf;
+	nand_chip->write_buf = atmel_write_buf;
 
 	platform_set_drvdata(pdev, host);
 	atmel_nand_enable(host);
···
 		printk(KERN_INFO "atmel_nand: Use On Flash BBT\n");
 		nand_chip->options |= NAND_USE_FLASH_BBT;
 	}
+
+	if (cpu_has_dma() && use_dma) {
+		dma_cap_mask_t mask;
+
+		dma_cap_zero(mask);
+		dma_cap_set(DMA_MEMCPY, mask);
+		host->dma_chan = dma_request_channel(mask, 0, NULL);
+		if (!host->dma_chan) {
+			dev_err(host->dev, "Failed to request DMA channel\n");
+			use_dma = 0;
+		}
+	}
+	if (use_dma)
+		dev_info(host->dev, "Using DMA for NAND access.\n");
+	else
+		dev_info(host->dev, "No DMA support for NAND access.\n");
 
 	/* first scan to find the device and get the page size */
 	if (nand_scan_ident(mtd, 1, NULL)) {
···
 err_no_card:
 	atmel_nand_disable(host);
 	platform_set_drvdata(pdev, NULL);
+	if (host->dma_chan)
+		dma_release_channel(host->dma_chan);
 	if (host->ecc)
 		iounmap(host->ecc);
 err_ecc_ioremap:
···
 
 	if (host->ecc)
 		iounmap(host->ecc);
+
+	if (host->dma_chan)
+		dma_release_channel(host->dma_chan);
+
 	iounmap(host->io_base);
 	kfree(host);