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Date:	Tue, 12 Aug 2014 18:21:38 +0200
From:	Ulf Hansson <ulf.hansson@...aro.org>
To:	Apelete Seketeli <apelete@...eteli.net>
Cc:	Chris Ball <chris@...ntf.net>,
	H Hartley Sweeten <hsweeten@...ionengravers.com>,
	Lars-Peter Clausen <lars@...afoo.de>,
	Wei Yongjun <yongjun_wei@...ndmicro.com.cn>,
	Alex Smith <alex.smith@...tec.com>,
	Laurent Pinchart <laurent.pinchart+renesas@...asonboard.com>,
	linux-mmc <linux-mmc@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v6 1/2] mmc: jz4740: add dma infrastructure for data transfers

On 21 July 2014 06:37, Apelete Seketeli <apelete@...eteli.net> 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@...eteli.net>

Thanks! Queued for 3.18.

Kind regards
Uffe

> ---
>  drivers/mmc/host/jz4740_mmc.c |  174 +++++++++++++++++++++++++++++++++++++++--
>  1 file changed, 166 insertions(+), 8 deletions(-)
>
> diff --git a/drivers/mmc/host/jz4740_mmc.c b/drivers/mmc/host/jz4740_mmc.c
> index 537d6c7..049b133 100644
> --- a/drivers/mmc/host/jz4740_mmc.c
> +++ b/drivers/mmc/host/jz4740_mmc.c
> @@ -30,7 +30,9 @@
>  #include <asm/mach-jz4740/gpio.h>
>  #include <asm/cacheflush.h>
>  #include <linux/dma-mapping.h>
> +#include <linux/dmaengine.h>
>
> +#include <asm/mach-jz4740/dma.h>
>  #include <asm/mach-jz4740/jz4740_mmc.h>
>
>  #define JZ_REG_MMC_STRPCL      0x00
> @@ -122,6 +124,7 @@ struct jz4740_mmc_host {
>         int card_detect_irq;
>
>         void __iomem *base;
> +       struct resource *mem_res;
>         struct mmc_request *req;
>         struct mmc_command *cmd;
>
> @@ -136,8 +139,138 @@ struct jz4740_mmc_host {
>         struct timer_list timeout_timer;
>         struct sg_mapping_iter miter;
>         enum jz4740_mmc_state state;
> +
> +       /* DMA support */
> +       struct dma_chan *dma_rx;
> +       struct dma_chan *dma_tx;
> +       bool use_dma;
> +       int sg_len;
> +
> +/* The DMA trigger level is 8 words, that is to say, the DMA read
> + * trigger is when data words in MSC_RXFIFO is >= 8 and the DMA write
> + * trigger is when data words in MSC_TXFIFO is < 8.
> + */
> +#define JZ4740_MMC_FIFO_HALF_SIZE 8
>  };
>
> +/*----------------------------------------------------------------------------*/
> +/* DMA infrastructure */
> +
> +static void jz4740_mmc_release_dma_channels(struct jz4740_mmc_host *host)
> +{
> +       if (!host->use_dma)
> +               return;
> +
> +       dma_release_channel(host->dma_tx);
> +       dma_release_channel(host->dma_rx);
> +}
> +
> +static int jz4740_mmc_acquire_dma_channels(struct jz4740_mmc_host *host)
> +{
> +       dma_cap_mask_t mask;
> +
> +       dma_cap_zero(mask);
> +       dma_cap_set(DMA_SLAVE, mask);
> +
> +       host->dma_tx = dma_request_channel(mask, NULL, host);
> +       if (!host->dma_tx) {
> +               dev_err(mmc_dev(host->mmc), "Failed to get dma_tx channel\n");
> +               return -ENODEV;
> +       }
> +
> +       host->dma_rx = dma_request_channel(mask, NULL, host);
> +       if (!host->dma_rx) {
> +               dev_err(mmc_dev(host->mmc), "Failed to get dma_rx channel\n");
> +               goto free_master_write;
> +       }
> +
> +       return 0;
> +
> +free_master_write:
> +       dma_release_channel(host->dma_tx);
> +       return -ENODEV;
> +}
> +
> +static inline int jz4740_mmc_get_dma_dir(struct mmc_data *data)
> +{
> +       return (data->flags & MMC_DATA_READ) ? DMA_FROM_DEVICE : DMA_TO_DEVICE;
> +}
> +
> +static void jz4740_mmc_dma_unmap(struct jz4740_mmc_host *host,
> +                                struct mmc_data *data)
> +{
> +       struct dma_chan *chan;
> +       enum dma_data_direction dir = jz4740_mmc_get_dma_dir(data);
> +
> +       if (dir == DMA_TO_DEVICE)
> +               chan = host->dma_tx;
> +       else
> +               chan = host->dma_rx;
> +
> +       dma_unmap_sg(chan->device->dev, data->sg, data->sg_len, dir);
> +}
> +
> +static int jz4740_mmc_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_mmc_get_dma_dir(data);
> +
> +       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;
> +       }
> +
> +       host->sg_len = dma_map_sg(chan->device->dev,
> +                                 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;
> +       }
> +
> +       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_mmc_dma_unmap(host, data);
> +       return -ENOMEM;
> +}
> +
> +/*----------------------------------------------------------------------------*/
> +
>  static void jz4740_mmc_set_irq_enabled(struct jz4740_mmc_host *host,
>         unsigned int irq, bool enabled)
>  {
> @@ -442,6 +575,8 @@ static void jz4740_mmc_send_command(struct jz4740_mmc_host *host,
>                         cmdat |= JZ_MMC_CMDAT_WRITE;
>                 if (cmd->data->flags & MMC_DATA_STREAM)
>                         cmdat |= JZ_MMC_CMDAT_STREAM;
> +               if (host->use_dma)
> +                       cmdat |= JZ_MMC_CMDAT_DMA_EN;
>
>                 writew(cmd->data->blksz, host->base + JZ_REG_MMC_BLKLEN);
>                 writew(cmd->data->blocks, host->base + JZ_REG_MMC_NOB);
> @@ -474,6 +609,7 @@ static irqreturn_t jz_mmc_irq_worker(int irq, void *devid)
>         struct jz4740_mmc_host *host = (struct jz4740_mmc_host *)devid;
>         struct mmc_command *cmd = host->req->cmd;
>         struct mmc_request *req = host->req;
> +       struct mmc_data *data = cmd->data;
>         bool timeout = false;
>
>         if (cmd->error)
> @@ -484,23 +620,32 @@ static irqreturn_t jz_mmc_irq_worker(int irq, void *devid)
>                 if (cmd->flags & MMC_RSP_PRESENT)
>                         jz4740_mmc_read_response(host, cmd);
>
> -               if (!cmd->data)
> +               if (!data)
>                         break;
>
>                 jz_mmc_prepare_data_transfer(host);
>
>         case JZ4740_MMC_STATE_TRANSFER_DATA:
> -               if (cmd->data->flags & MMC_DATA_READ)
> -                       timeout = jz4740_mmc_read_data(host, cmd->data);
> +               if (host->use_dma) {
> +                       /* Use DMA if enabled, data transfer direction was
> +                        * defined  before in jz_mmc_prepare_data_transfer().
> +                        */
> +                       timeout = jz4740_mmc_start_dma_transfer(host, data);
> +                       data->bytes_xfered = data->blocks * data->blksz;
> +               } else if (data->flags & MMC_DATA_READ)
> +                       /* If DMA is not enabled, rely on data flags
> +                        * to establish data transfer direction.
> +                        */
> +                       timeout = jz4740_mmc_read_data(host, data);
>                 else
> -                       timeout = jz4740_mmc_write_data(host, cmd->data);
> +                       timeout = jz4740_mmc_write_data(host, data);
>
>                 if (unlikely(timeout)) {
>                         host->state = JZ4740_MMC_STATE_TRANSFER_DATA;
>                         break;
>                 }
>
> -               jz4740_mmc_transfer_check_state(host, cmd->data);
> +               jz4740_mmc_transfer_check_state(host, data);
>
>                 timeout = jz4740_mmc_poll_irq(host, JZ_MMC_IRQ_DATA_TRAN_DONE);
>                 if (unlikely(timeout)) {
> @@ -757,7 +902,6 @@ static int jz4740_mmc_probe(struct platform_device* pdev)
>         struct mmc_host *mmc;
>         struct jz4740_mmc_host *host;
>         struct jz4740_mmc_platform_data *pdata;
> -       struct resource *res;
>
>         pdata = pdev->dev.platform_data;
>
> @@ -784,10 +928,11 @@ 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);
> +       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;
>         }
>
> @@ -834,6 +979,10 @@ static int jz4740_mmc_probe(struct platform_device* pdev)
>         /* It is not important when it times out, it just needs to timeout. */
>         set_timer_slack(&host->timeout_timer, HZ);
>
> +       host->use_dma = true;
> +       if (host->use_dma && jz4740_mmc_acquire_dma_channels(host) != 0)
> +               host->use_dma = false;
> +
>         platform_set_drvdata(pdev, host);
>         ret = mmc_add_host(mmc);
>
> @@ -843,6 +992,10 @@ static int jz4740_mmc_probe(struct platform_device* pdev)
>         }
>         dev_info(&pdev->dev, "JZ SD/MMC card driver registered\n");
>
> +       dev_info(&pdev->dev, "Using %s, %d-bit mode\n",
> +                host->use_dma ? "DMA" : "PIO",
> +                (mmc->caps & MMC_CAP_4_BIT_DATA) ? 4 : 1);
> +
>         return 0;
>
>  err_free_irq:
> @@ -850,6 +1003,8 @@ err_free_irq:
>  err_free_gpios:
>         jz4740_mmc_free_gpios(pdev);
>  err_gpio_bulk_free:
> +       if (host->use_dma)
> +               jz4740_mmc_release_dma_channels(host);
>         jz_gpio_bulk_free(jz4740_mmc_pins, jz4740_mmc_num_pins(host));
>  err_free_host:
>         mmc_free_host(mmc);
> @@ -872,6 +1027,9 @@ static int jz4740_mmc_remove(struct platform_device *pdev)
>         jz4740_mmc_free_gpios(pdev);
>         jz_gpio_bulk_free(jz4740_mmc_pins, jz4740_mmc_num_pins(host));
>
> +       if (host->use_dma)
> +               jz4740_mmc_release_dma_channels(host);
> +
>         mmc_free_host(host->mmc);
>
>         return 0;
> --
> 1.7.10.4
>
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