mmc: at91_mci: use one coherent DMA buffer
Wolfgang Muees [Fri, 5 Mar 2010 21:43:40 +0000 (13:43 -0800)]
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.

[nicolas.ferre@atmel.com: coding style modifications]
Signed-off-by: Wolfgang Muees <wolfgang.mues@auerswald.de>
Signed-off-by: Nicolas Ferre <nicolas.ferre@atmel.com>
Cc: Andrew Victor <avictor.za@gmail.com>
Cc: <linux-mmc@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

drivers/mmc/host/at91_mci.c

index 37efe6b..76cb05a 100644 (file)
 #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);