[MMC] Add multi block-write capability

Add a capability flag for drivers to set when they can perform multi-
block transfers to cards _and_ correctly report the number of bytes
transferred should an error occur.

The last point is very important - if a driver reports more bytes than
were actually accepted by the card and an error occurs, there is the
possibility for data loss.

Pierre Ossman provided the patch for wbsd and sdhci.

Signed-off-by: Pierre Ossman <drzeus@drzeus.cx>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

1 files changed, 20 insertions, 7 deletions

diff --git a/drivers/mmc/mmc_block.c b/drivers/mmc/mmc_block.c
index f3a99dd8df8f..8d18b87bfd34 100644
--- a/drivers/mmc/mmc_block.c
+++ b/drivers/mmc/mmc_block.c
@@ -32,6 +32,7 @@
 #include <linux/mmc/card.h>
 #include <linux/mmc/host.h>
 #include <linux/mmc/protocol.h>
+#include <linux/mmc/host.h>
 
 #include <asm/system.h>
 #include <asm/uaccess.h>
@@ -165,6 +166,7 @@ static int mmc_blk_issue_rq(struct mmc_queue *mq, struct request *req)
         do {
                 struct mmc_blk_request brq;
                 struct mmc_command cmd;
+                u32 readcmd, writecmd;
 
                 memset(&brq, 0, sizeof(struct mmc_blk_request));
                 brq.mrq.cmd = &brq.cmd;
@@ -180,20 +182,31 @@ static int mmc_blk_issue_rq(struct mmc_queue *mq, struct request *req)
 
                 mmc_set_data_timeout(&brq.data, card, rq_data_dir(req) != READ);
 
-                if (rq_data_dir(req) == READ) {
-                        brq.cmd.opcode = brq.data.blocks > 1 ? MMC_READ_MULTIPLE_BLOCK : MMC_READ_SINGLE_BLOCK;
-                        brq.data.flags |= MMC_DATA_READ;
-                } else {
-                        brq.cmd.opcode = MMC_WRITE_BLOCK;
-                        brq.data.flags |= MMC_DATA_WRITE;
+                /*
+                 * If the host doesn't support multiple block writes, force
+                 * block writes to single block.
+                 */
+                if (rq_data_dir(req) != READ &&
+                    !(card->host->caps & MMC_CAP_MULTIWRITE))
                         brq.data.blocks = 1;
-                }
 
                 if (brq.data.blocks > 1) {
                         brq.data.flags |= MMC_DATA_MULTI;
                         brq.mrq.stop = &brq.stop;
+                        readcmd = MMC_READ_MULTIPLE_BLOCK;
+                        writecmd = MMC_WRITE_MULTIPLE_BLOCK;
                 } else {
                         brq.mrq.stop = NULL;
+                        readcmd = MMC_READ_SINGLE_BLOCK;
+                        writecmd = MMC_WRITE_BLOCK;
+                }
+
+                if (rq_data_dir(req) == READ) {
+                        brq.cmd.opcode = readcmd;
+                        brq.data.flags |= MMC_DATA_READ;
+                } else {
+                        brq.cmd.opcode = writecmd;
+                        brq.data.flags |= MMC_DATA_WRITE;
                 }
 
                 brq.data.sg = mq->sg;