linux-kernel - Re: [PATCH v4] MTD: LPC32xx SLC NAND driver

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Message-ID: <20120603190932.GB23368@n2100.arm.linux.org.uk>
Date:	Sun, 3 Jun 2012 20:09:32 +0100
From:	Russell King - ARM Linux <linux@....linux.org.uk>
To:	Roland Stigge <stigge@...com.de>
Cc:	linux-mtd@...ts.infradead.org, linux-kernel@...r.kernel.org,
	linux-doc@...r.kernel.org, devicetree-discuss@...ts.ozlabs.org,
	dwmw2@...radead.org, kevin.wells@....com, srinivas.bakki@....com,
	linux-arm-kernel@...ts.infradead.org, hechtb@...glemail.com,
	lars@...afoo.de, b32955@...escale.com, leiwen@...vell.com,
	dedekind1@...il.com
Subject: Re: [PATCH v4] MTD: LPC32xx SLC NAND driver

On Sun, Jun 03, 2012 at 08:38:09PM +0200, Roland Stigge wrote:
> +static int lpc32xx_xmit_dma(struct mtd_info *mtd, dma_addr_t dma,
> +			    void *mem, int len, enum dma_transfer_direction dir)
> +{
> +	struct nand_chip *chip = mtd->priv;
> +	struct lpc32xx_nand_host *host = chip->priv;
> +	struct dma_async_tx_descriptor *desc;
> +	int flags = DMA_CTRL_ACK | DMA_PREP_INTERRUPT;
> +	int res;
> +	dma_cookie_t cookie;
> +
> +	host->dma_slave_config.direction = dir;
> +	host->dma_slave_config.src_addr = dma;
> +	host->dma_slave_config.dst_addr = dma;
> +	host->dma_slave_config.src_addr_width = DMA_SLAVE_BUSWIDTH_4_BYTES;
> +	host->dma_slave_config.dst_addr_width = DMA_SLAVE_BUSWIDTH_4_BYTES;
> +	host->dma_slave_config.src_maxburst = 4;
> +	host->dma_slave_config.dst_maxburst = 4;
> +	/* DMA controller does flow control: */
> +	host->dma_slave_config.device_fc = false;
> +	if (dmaengine_slave_config(host->dma_chan, &host->dma_slave_config)) {
> +		dev_err(mtd->dev.parent, "Failed to setup DMA slave\n");
> +		return -ENXIO;
> +	}
> +
> +	sg_init_one(&host->sgl, mem, len);
> +
> +	res = dma_map_sg(host->dma_chan->device->dev, &host->sgl, 1,
> +			 DMA_BIDIRECTIONAL);
> +	if (res != 1) {
> +		dev_err(mtd->dev.parent, "Failed to map sg list\n");
> +		return -ENXIO;
> +	}
> +	desc = dmaengine_prep_slave_sg(host->dma_chan, &host->sgl, 1, dir,
> +				       flags);
> +	if (!desc) {
> +		dev_err(mtd->dev.parent, "Failed to prepare slave sg\n");
> +		goto out1;
> +	}
> +
> +	init_completion(&host->comp);
> +	desc->callback = lpc32xx_dma_complete_func;
> +	desc->callback_param = &host->comp;
> +
> +	cookie = dmaengine_submit(desc);
> +	if (dma_submit_error(cookie)) {
> +		dev_err(mtd->dev.parent, "Failed to dmaengine_submit()\n");
> +		goto out1;
> +	}

dmaengine_submit() is no longer allowed to fail, so you don't need this
check here anymore.  It's been that way for a long time.

> +	dma_async_issue_pending(host->dma_chan);
> +
> +	wait_for_completion_timeout(&host->comp, msecs_to_jiffies(1000));

What about unmapping the buffer upon completion?

> +
> +	return 0;
> +out1:
> +	dma_unmap_sg(host->dma_chan->device->dev, &host->sgl, 1,
> +		     DMA_BIDIRECTIONAL);
> +	return -ENXIO;
> +}
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