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    Subject[PATCH 3/7] mmc: at91_mci: use one coherent DMA buffer
    Date
    From: Wolfgang Muees <wolfgang.mues@auerswald.de>

    The TX DMA buffer is allocated only once, because the allocation/deallocation
    of the buffer for EACH chunk of data is time-consuming and prone to memory
    fragmentation.

    Using a coherent DMA buffer avoids extra data cache calls.

    Signed-off-by: Wolfgang Muees <wolfgang.mues@auerswald.de>
    [nicolas.ferre@atmel.com: coding style modifications]
    Signed-off-by: Nicolas Ferre <nicolas.ferre@atmel.com>
    ---
    drivers/mmc/host/at91_mci.c | 49 +++++++++++++++++++++----------------------
    1 files changed, 24 insertions(+), 25 deletions(-)

    diff --git a/drivers/mmc/host/at91_mci.c b/drivers/mmc/host/at91_mci.c
    index f2cb716..fd01195 100644
    --- a/drivers/mmc/host/at91_mci.c
    +++ b/drivers/mmc/host/at91_mci.c
    @@ -88,6 +88,10 @@
    #define at91_mci_read(host, reg) __raw_readl((host)->baseaddr + (reg))
    #define at91_mci_write(host, reg, val) __raw_writel((val), (host)->baseaddr + (reg))

    +#define MCI_BLKSIZE 512
    +#define MCI_MAXBLKSIZE 4095
    +#define MCI_BLKATONCE 256
    +#define MCI_BUFSIZE (MCI_BLKSIZE * MCI_BLKATONCE)

    /*
    * Low level type for this driver
    @@ -604,7 +608,6 @@ static void at91_mci_send_command(struct at91mci_host *host, struct mmc_command
    /*
    * Handle a read
    */
    - host->buffer = NULL;
    host->total_length = 0;

    at91_mci_pre_dma_read(host);
    @@ -623,20 +626,8 @@ static void at91_mci_send_command(struct at91mci_host *host, struct mmc_command
    if (host->total_length < 12)
    host->total_length = 12;

    - host->buffer = kmalloc(host->total_length, GFP_KERNEL);
    - if (!host->buffer) {
    - pr_debug("Can't alloc tx buffer\n");
    - cmd->error = -ENOMEM;
    - mmc_request_done(host->mmc, host->request);
    - return;
    - }
    -
    at91_mci_sg_to_dma(host, data);

    - host->physical_address = dma_map_single(NULL,
    - host->buffer, host->total_length,
    - DMA_TO_DEVICE);
    -
    pr_debug("Transmitting %d bytes\n", host->total_length);

    at91_mci_write(host, ATMEL_PDC_TPR, host->physical_address);
    @@ -703,14 +694,6 @@ static void at91_mci_completed_command(struct at91mci_host *host, unsigned int s
    cmd->resp[2] = at91_mci_read(host, AT91_MCI_RSPR(2));
    cmd->resp[3] = at91_mci_read(host, AT91_MCI_RSPR(3));

    - if (host->buffer) {
    - dma_unmap_single(NULL,
    - host->physical_address, host->total_length,
    - DMA_TO_DEVICE);
    - kfree(host->buffer);
    - host->buffer = NULL;
    - }
    -
    pr_debug("Status = %08X/%08x [%08X %08X %08X %08X]\n",
    status, at91_mci_read(host, AT91_MCI_SR),
    cmd->resp[0], cmd->resp[1], cmd->resp[2], cmd->resp[3]);
    @@ -1012,12 +995,12 @@ static int __init at91_mci_probe(struct platform_device *pdev)
    mmc->ocr_avail = MMC_VDD_32_33 | MMC_VDD_33_34;
    mmc->caps = MMC_CAP_SDIO_IRQ;

    - mmc->max_blk_size = 4095;
    - mmc->max_blk_count = mmc->max_req_size;
    + mmc->max_blk_size = MCI_MAXBLKSIZE;
    + mmc->max_blk_count = MCI_BLKATONCE;
    + mmc->max_req_size = MCI_BUFSIZE;

    host = mmc_priv(mmc);
    host->mmc = mmc;
    - host->buffer = NULL;
    host->bus_mode = 0;
    host->board = pdev->dev.platform_data;
    if (host->board->wire4) {
    @@ -1028,6 +1011,14 @@ static int __init at91_mci_probe(struct platform_device *pdev)
    " - using 1 wire\n");
    }

    + host->buffer = dma_alloc_coherent(&pdev->dev, MCI_BUFSIZE,
    + &host->physical_address, GFP_KERNEL);
    + if (!host->buffer) {
    + ret = -ENOMEM;
    + dev_err(&pdev->dev, "Can't allocate transmit buffer\n");
    + goto fail5;
    + }
    +
    /*
    * Reserve GPIOs ... board init code makes sure these pins are set
    * up as GPIOs with the right direction (input, except for vcc)
    @@ -1036,7 +1027,7 @@ static int __init at91_mci_probe(struct platform_device *pdev)
    ret = gpio_request(host->board->det_pin, "mmc_detect");
    if (ret < 0) {
    dev_dbg(&pdev->dev, "couldn't claim card detect pin\n");
    - goto fail5;
    + goto fail4b;
    }
    }
    if (host->board->wp_pin) {
    @@ -1136,6 +1127,10 @@ fail3:
    fail4:
    if (host->board->det_pin)
    gpio_free(host->board->det_pin);
    +fail4b:
    + if (host->buffer)
    + dma_free_coherent(&pdev->dev, MCI_BUFSIZE,
    + host->buffer, host->physical_address);
    fail5:
    mmc_free_host(mmc);
    fail6:
    @@ -1158,6 +1153,10 @@ static int __exit at91_mci_remove(struct platform_device *pdev)

    host = mmc_priv(mmc);

    + if (host->buffer)
    + dma_free_coherent(&pdev->dev, MCI_BUFSIZE,
    + host->buffer, host->physical_address);
    +
    if (host->board->det_pin) {
    if (device_can_wakeup(&pdev->dev))
    free_irq(gpio_to_irq(host->board->det_pin), host);
    --
    1.5.6.5


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