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Message-ID: <20110114100013.GH2822@pulham.picochip.com>
Date: Fri, 14 Jan 2011 10:00:13 +0000
From: Jamie Iles <jamie@...ieiles.com>
To: Hong Xu <hong.xu@...el.com>
Cc: linux-mtd@...ts.infradead.org,
linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
nicolas.ferre@...el.com
Subject: Re: [PATCH] MTD: atmel_nand: Add DMA support to access Nandflash
Hi Hong,
A couple of minor comments inline but otherwise looks good to me.
Jamie
On Fri, Jan 14, 2011 at 05:34:47PM +0800, Hong Xu wrote:
> diff --git a/drivers/mtd/nand/atmel_nand.c
> b/drivers/mtd/nand/atmel_nand.c
> index ccce0f0..c2fbffe 100644
> --- a/drivers/mtd/nand/atmel_nand.c
> +++ b/drivers/mtd/nand/atmel_nand.c
> @@ -48,6 +48,12 @@
> #define no_ecc 0
> #endif
>
> +/* DMA for large buffers only */
> +#define DMA_MIN_BYTES 512
> +
Is it worth making this a module parameter and defaulting to 512?
> +static int use_dma = 1;
> +module_param(use_dma, int, 0);
> +
> static int on_flash_bbt = 0;
> module_param(on_flash_bbt, int, 0);
>
> @@ -89,11 +95,20 @@ struct atmel_nand_host {
> struct nand_chip nand_chip;
> struct mtd_info mtd;
> void __iomem *io_base;
> + void __iomem *io_phys;
This should be of type dma_addr_t and this will eliminate some casting
later.
> 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.
> */
> @@ -150,7 +165,7 @@ static int atmel_nand_device_ready(struct mtd_info *mtd)
> /*
> * 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;
>
> @@ -164,7 +179,7 @@ static void atmel_read_buf16(struct mtd_info *mtd, u8 *buf, int len)
> __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;
>
> @@ -178,6 +193,102 @@ static void atmel_write_buf16(struct mtd_info *mtd, const u8 *buf, int len)
> __raw_writesw(nand_chip->IO_ADDR_W, buf, len / 2);
> }
>
> +static void dma_complete_func(void *completion)
> +{
> + complete(completion);
> +}
> +
> +static void 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;
> +
> + dma_dev = host->dma_chan->device;
> +
> + flags = DMA_CTRL_ACK | DMA_COMPL_SKIP_DEST_UNMAP | DMA_PREP_INTERRUPT |
> + DMA_COMPL_SKIP_SRC_UNMAP;
> +
> + if (is_read)
> + phys_addr = dma_map_single(dma_dev->dev, buf, len,
> + DMA_FROM_DEVICE);
> + else
> + phys_addr = dma_map_single(dma_dev->dev, buf, len,
> + DMA_TO_DEVICE);
> + if (!phys_addr) {
> + dev_err(host->dev, "Failed to dma_map_single\n");
> + goto err_dma_map;
> + }
I don't think this is right - you should check phys_addr() with
dma_mapping_error() rather than comparing to 0.
> +
> + if (is_read) {
> + dma_src_addr = (dma_addr_t)host->io_phys;
> + dma_dst_addr = phys_addr;
> + } else {
> + dma_src_addr = phys_addr;
> + dma_dst_addr = (dma_addr_t)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;
> + }
> +
> + 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_async_issue_pending(host->dma_chan);
> +
> + wait_for_completion(&host->comp);
> +
> +err:
> + if (is_read)
> + dma_unmap_single(dma_dev->dev, phys_addr, len, DMA_FROM_DEVICE);
> + else
> + dma_unmap_single(dma_dev->dev, phys_addr, len, DMA_TO_DEVICE);
> +err_dma_map:
> + return;
> +}
> +
> +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 >= DMA_MIN_BYTES)
> + atmel_nand_dma_op(mtd, buf, len, 1);
> + else 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 >= DMA_MIN_BYTES)
> + atmel_nand_dma_op(mtd, (u8 *)buf, len, 0);
> + else if (host->board->bus_width_16)
> + atmel_write_buf16(mtd, buf, len);
> + else
> + atmel_write_buf8(mtd, buf, len);
> +}
> +
> /*
> * Calculate HW ECC
> *
> @@ -398,6 +509,8 @@ static int __init atmel_nand_probe(struct platform_device *pdev)
> return -ENOMEM;
> }
>
> + host->io_phys = (void __iomem *)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");
> @@ -516,6 +629,23 @@ static int __init atmel_nand_probe(struct platform_device *pdev)
> }
> }
>
> + 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");
> +
> /* second phase scan */
> if (nand_scan_tail(mtd)) {
> res = -ENXIO;
> @@ -555,6 +685,8 @@ err_scan_ident:
> 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:
> @@ -578,6 +710,10 @@ static int __exit atmel_nand_remove(struct platform_device *pdev)
>
> if (host->ecc)
> iounmap(host->ecc);
> +
> + if (host->dma_chan)
> + dma_release_channel(host->dma_chan);
> +
> iounmap(host->io_base);
> kfree(host);
>
> --
> 1.7.3.3
>
>
> _______________________________________________
> linux-arm-kernel mailing list
> linux-arm-kernel@...ts.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
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