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SubjectRe: [PATCH v3] mmc: jz4740: add dma infrastructure for data transfers
Date
Hi Apelete,

Thank you for the patch.

On Friday 11 July 2014 00:27:26 Apelete Seketeli wrote:
> Until now the MMC driver for JZ4740 SoC was relying on PIO mode only
> for data transfers.
> This patch allows the use of DMA for data trasnfers in addition to PIO
> mode by relying on DMA Engine.
>
> DMA tranfers performance might be further improved by taking advantage
> of the asynchronous request capability of the MMC framework.
>
> Signed-off-by: Apelete Seketeli <apelete@seketeli.net>
> ---
> drivers/mmc/host/jz4740_mmc.c | 172 +++++++++++++++++++++++++++++++++++++--
> 1 file changed, 164
> insertions(+), 8 deletions(-)
>
> diff --git a/drivers/mmc/host/jz4740_mmc.c b/drivers/mmc/host/jz4740_mmc.c
> index 537d6c7..2897b49 100644
> --- a/drivers/mmc/host/jz4740_mmc.c
> +++ b/drivers/mmc/host/jz4740_mmc.c

[snip]

> +static void jz4740_dma_unmap(struct jz4740_mmc_host *host,
> + struct mmc_data *data)
> +{
> + enum dma_data_direction dir = jz4740_get_dma_dir(data);
> +
> + dma_unmap_sg(mmc_dev(host->mmc), data->sg, data->sg_len, dir);
> +}
> +
> +static int jz4740_start_dma_transfer(struct jz4740_mmc_host *host,
> + struct mmc_data *data)
> +{
> + struct dma_chan *chan;
> + struct dma_async_tx_descriptor *desc;
> + struct dma_slave_config conf = {
> + .src_addr_width = DMA_SLAVE_BUSWIDTH_4_BYTES,
> + .dst_addr_width = DMA_SLAVE_BUSWIDTH_4_BYTES,
> + .src_maxburst = JZ4740_MMC_FIFO_HALF_SIZE,
> + .dst_maxburst = JZ4740_MMC_FIFO_HALF_SIZE,
> + };
> + enum dma_data_direction dir = jz4740_get_dma_dir(data);
> +
> + host->sg_len = dma_map_sg(mmc_dev(host->mmc),

You should use the DMA engine device here, not the MMC device, as the memory
transfers will be performed by the DMA engine. Same for the dma_unmap_sg()
call above.

> + data->sg,
> + data->sg_len,
> + dir);
> +
> + if (host->sg_len < 0) {
> + dev_err(mmc_dev(host->mmc),
> + "Failed to map scatterlist for DMA operation\n");
> + return -EINVAL;
> + }
> +
> + if (dir == DMA_TO_DEVICE) {
> + conf.direction = DMA_MEM_TO_DEV;
> + conf.dst_addr = host->mem_res->start + JZ_REG_MMC_TXFIFO;
> + conf.slave_id = JZ4740_DMA_TYPE_MMC_TRANSMIT;
> + chan = host->dma_tx;
> + } else {
> + conf.direction = DMA_DEV_TO_MEM;
> + conf.src_addr = host->mem_res->start + JZ_REG_MMC_RXFIFO;
> + conf.slave_id = JZ4740_DMA_TYPE_MMC_RECEIVE;
> + chan = host->dma_rx;
> + }
> +
> + dmaengine_slave_config(chan, &conf);
> + desc = dmaengine_prep_slave_sg(chan,
> + data->sg,
> + host->sg_len,
> + conf.direction,
> + DMA_PREP_INTERRUPT | DMA_CTRL_ACK);
> + if (!desc) {
> + dev_err(mmc_dev(host->mmc),
> + "Failed to allocate DMA %s descriptor",
> + conf.direction == DMA_MEM_TO_DEV ? "TX" : "RX");
> + goto dma_unmap;
> + }
> +
> + dmaengine_submit(desc);
> + dma_async_issue_pending(chan);
> +
> + return 0;
> +
> +dma_unmap:
> + jz4740_dma_unmap(host, data);
> + return -ENOMEM;
> +}
> +
> +/*-------------------------------------------------------------------------
> ---*/ +
> static void jz4740_mmc_set_irq_enabled(struct jz4740_mmc_host *host,
> unsigned int irq, bool enabled)
> {

[snip]

> @@ -784,10 +922,17 @@ static int jz4740_mmc_probe(struct platform_device*
> pdev) goto err_free_host;
> }
>
> - res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> - host->base = devm_ioremap_resource(&pdev->dev, res);
> + host->mem_res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> + if (!host->mem_res) {
> + ret = -EBUSY;
> + dev_err(&pdev->dev, "Failed to request memory region\n");
> + goto err_free_host;

The devm_ioremap_resource() call below will handle the mem_res == NULL case
and print a message, so you could remove this check.

> + }
> +
> + host->base = devm_ioremap_resource(&pdev->dev, host->mem_res);
> if (IS_ERR(host->base)) {
> ret = PTR_ERR(host->base);
> + dev_err(&pdev->dev, "Failed to ioremap base memory\n");
> goto err_free_host;
> }
>

[snip]

--
Regards,

Laurent Pinchart



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