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Subject[PATCH RESEND] mmc: sdio: rw extended, use a sg entry for each block
Date
While using io multiple blocks operations, change the way that sg is built:
use one sg entry for each block instead of aggregating the whole buffer
in a single sg entry.
Using a single sg entry for a multiple block command may lead to
misunderstanding between the sd/mmc and the DMA controllers. In fact, the
knowledge of the block length will allow both controllers to optimize burst
sizes on internal bus while dealing with those data.

Use a sg table to store start addresses of blocks within the data buffer.

Signed-off-by: Nicolas Ferre <nicolas.ferre@atmel.com>
---
drivers/mmc/core/sdio_ops.c | 38 +++++++++++++++++++++++++++++---------
1 files changed, 29 insertions(+), 9 deletions(-)

diff --git a/drivers/mmc/core/sdio_ops.c b/drivers/mmc/core/sdio_ops.c
index f087d87..aea6978 100644
--- a/drivers/mmc/core/sdio_ops.c
+++ b/drivers/mmc/core/sdio_ops.c
@@ -124,7 +124,7 @@ int mmc_io_rw_extended(struct mmc_card *card, int write, unsigned fn,
struct mmc_request mrq = {0};
struct mmc_command cmd = {0};
struct mmc_data data = {0};
- struct scatterlist sg;
+ struct sg_table sgt;

BUG_ON(!card);
BUG_ON(fn > 7);
@@ -144,24 +144,44 @@ int mmc_io_rw_extended(struct mmc_card *card, int write, unsigned fn,
cmd.arg |= fn << 28;
cmd.arg |= incr_addr ? 0x04000000 : 0x00000000;
cmd.arg |= addr << 9;
- if (blocks == 1 && blksz <= 512)
- cmd.arg |= (blksz == 512) ? 0 : blksz; /* byte mode */
- else
- cmd.arg |= 0x08000000 | blocks; /* block mode */
+ if (blocks == 1 && blksz <= 512) {
+ /* byte mode */
+ struct scatterlist sg;
+
+ cmd.arg |= (blksz == 512) ? 0 : blksz;
+ sg_init_one(&sg, buf, blksz * blocks);
+
+ data.sg = &sg;
+ data.sg_len = 1;
+ } else {
+ /* block mode */
+ struct scatterlist *sg_ptr;
+ int i;
+
+ cmd.arg |= 0x08000000 | blocks;
+ if (sg_alloc_table(&sgt, blocks, GFP_KERNEL))
+ return -ENOMEM;
+ for_each_sg(sgt.sgl, sg_ptr, sgt.nents, i) {
+ sg_set_buf(sg_ptr, buf + i * blksz, blksz);
+ }
+
+ data.sg = sgt.sgl;
+ data.sg_len = sgt.nents;
+ }
+
cmd.flags = MMC_RSP_SPI_R5 | MMC_RSP_R5 | MMC_CMD_ADTC;

data.blksz = blksz;
data.blocks = blocks;
data.flags = write ? MMC_DATA_WRITE : MMC_DATA_READ;
- data.sg = &sg;
- data.sg_len = 1;
-
- sg_init_one(&sg, buf, blksz * blocks);

mmc_set_data_timeout(&data, card);

mmc_wait_for_req(card->host, &mrq);

+ if (blocks != 1 || blksz > 512)
+ sg_free_table(&sgt);
+
if (cmd.error)
return cmd.error;
if (data.error)
--
1.7.3


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