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Subject[PATCH 4/7] mmc: at91_mci: use DMA buffer for read
Date
From: Wolfgang Muees <wolfgang.mues@auerswald.de>

This patch converts the read to use the DMA buffer as well. The old
code was doing double-buffering DMA with the PDC; no way to make it
work. Replace it with a single-PDC approach.
It also simplify things removing the need for a pre_dma_read() function.

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 | 128 +++++++++++--------------------------------
1 files changed, 32 insertions(+), 96 deletions(-)
diff --git a/drivers/mmc/host/at91_mci.c b/drivers/mmc/host/at91_mci.c
index fd01195..28fd565 100644
--- a/drivers/mmc/host/at91_mci.c
+++ b/drivers/mmc/host/at91_mci.c
@@ -251,80 +251,14 @@ static inline void at91_mci_sg_to_dma(struct at91mci_host *host, struct mmc_data
}

/*
- * Prepare a dma read
- */
-static void at91_mci_pre_dma_read(struct at91mci_host *host)
-{
- int i;
- struct scatterlist *sg;
- struct mmc_command *cmd;
- struct mmc_data *data;
-
- pr_debug("pre dma read\n");
-
- cmd = host->cmd;
- if (!cmd) {
- pr_debug("no command\n");
- return;
- }
-
- data = cmd->data;
- if (!data) {
- pr_debug("no data\n");
- return;
- }
-
- for (i = 0; i < 2; i++) {
- /* nothing left to transfer */
- if (host->transfer_index >= data->sg_len) {
- pr_debug("Nothing left to transfer (index = %d)\n", host->transfer_index);
- break;
- }
-
- /* Check to see if this needs filling */
- if (i == 0) {
- if (at91_mci_read(host, ATMEL_PDC_RCR) != 0) {
- pr_debug("Transfer active in current\n");
- continue;
- }
- }
- else {
- if (at91_mci_read(host, ATMEL_PDC_RNCR) != 0) {
- pr_debug("Transfer active in next\n");
- continue;
- }
- }
-
- /* Setup the next transfer */
- pr_debug("Using transfer index %d\n", host->transfer_index);
-
- sg = &data->sg[host->transfer_index++];
- pr_debug("sg = %p\n", sg);
-
- sg->dma_address = dma_map_page(NULL, sg_page(sg), sg->offset, sg->length, DMA_FROM_DEVICE);
-
- pr_debug("dma address = %08X, length = %d\n", sg->dma_address, sg->length);
-
- if (i == 0) {
- at91_mci_write(host, ATMEL_PDC_RPR, sg->dma_address);
- at91_mci_write(host, ATMEL_PDC_RCR, (data->blksz & 0x3) ? sg->length : sg->length / 4);
- }
- else {
- at91_mci_write(host, ATMEL_PDC_RNPR, sg->dma_address);
- at91_mci_write(host, ATMEL_PDC_RNCR, (data->blksz & 0x3) ? sg->length : sg->length / 4);
- }
- }
-
- pr_debug("pre dma read done\n");
-}
-
-/*
* Handle after a dma read
*/
static void at91_mci_post_dma_read(struct at91mci_host *host)
{
struct mmc_command *cmd;
struct mmc_data *data;
+ unsigned int len, i, size;
+ unsigned *dmabuf = host->buffer;

pr_debug("post dma read\n");

@@ -340,42 +274,39 @@ static void at91_mci_post_dma_read(struct at91mci_host *host)
return;
}

- while (host->in_use_index < host->transfer_index) {
- struct scatterlist *sg;
+ size = data->blksz * data->blocks;
+ len = data->sg_len;

- pr_debug("finishing index %d\n", host->in_use_index);
+ at91_mci_write(host, AT91_MCI_IDR, AT91_MCI_ENDRX);
+ at91_mci_write(host, AT91_MCI_IER, AT91_MCI_RXBUFF);

- sg = &data->sg[host->in_use_index++];
+ for (i = 0; i < len; i++) {
+ struct scatterlist *sg;
+ int amount;
+ unsigned int *sgbuffer;

- pr_debug("Unmapping page %08X\n", sg->dma_address);
+ sg = &data->sg[i];

- dma_unmap_page(NULL, sg->dma_address, sg->length, DMA_FROM_DEVICE);
+ sgbuffer = kmap_atomic(sg_page(sg), KM_BIO_SRC_IRQ) + sg->offset;
+ amount = min(size, sg->length);
+ size -= amount;

if (cpu_is_at91rm9200()) { /* AT91RM9200 errata */
- unsigned int *buffer;
int index;
-
- /* Swap the contents of the buffer */
- buffer = kmap_atomic(sg_page(sg), KM_BIO_SRC_IRQ) + sg->offset;
- pr_debug("buffer = %p, length = %d\n", buffer, sg->length);
-
- for (index = 0; index < (sg->length / 4); index++)
- buffer[index] = swab32(buffer[index]);
-
- kunmap_atomic(buffer, KM_BIO_SRC_IRQ);
+ for (index = 0; index < (amount / 4); index++)
+ sgbuffer[index] = swab32(*dmabuf++);
+ } else {
+ char *tmpv = (char *)dmabuf;
+ memcpy(sgbuffer, tmpv, amount);
+ tmpv += amount;
+ dmabuf = (unsigned *)tmpv;
}

- flush_dcache_page(sg_page(sg));
-
- data->bytes_xfered += sg->length;
- }
-
- /* Is there another transfer to trigger? */
- if (host->transfer_index < data->sg_len)
- at91_mci_pre_dma_read(host);
- else {
- at91_mci_write(host, AT91_MCI_IDR, AT91_MCI_ENDRX);
- at91_mci_write(host, AT91_MCI_IER, AT91_MCI_RXBUFF);
+ kunmap_atomic(((void *)sgbuffer)-sg->offset, KM_BIO_SRC_IRQ);
+ dmac_flush_range((void *)sgbuffer, ((void *)sgbuffer) + amount);
+ data->bytes_xfered += amount;
+ if (size == 0)
+ break;
}

pr_debug("post dma read done\n");
@@ -610,7 +541,12 @@ static void at91_mci_send_command(struct at91mci_host *host, struct mmc_command
*/
host->total_length = 0;

- at91_mci_pre_dma_read(host);
+ at91_mci_write(host, ATMEL_PDC_RPR, host->physical_address);
+ at91_mci_write(host, ATMEL_PDC_RCR, (data->blksz & 0x3) ?
+ (blocks * block_length) : (blocks * block_length) / 4);
+ at91_mci_write(host, ATMEL_PDC_RNPR, 0);
+ at91_mci_write(host, ATMEL_PDC_RNCR, 0);
+
ier = AT91_MCI_ENDRX /* | AT91_MCI_RXBUFF */;
}
else {
--
1.5.6.5


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