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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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