mmc: bounce requests for simple hosts

Some hosts cannot do scatter/gather in hardware. Since not doing sg
is such a big performance hit, we (optionally) bounce the requests
to a simple linear buffer that we hand over to the driver.

Signed-off-by: Pierre Ossman <drzeus@drzeus.cx>

1 files changed, 6 insertions, 1 deletions

diff --git a/drivers/mmc/card/block.c b/drivers/mmc/card/block.c
index 540ff4bea54c..cbd4b6e3e17c 100644
--- a/drivers/mmc/card/block.c
+++ b/drivers/mmc/card/block.c
@@ -262,7 +262,9 @@ static int mmc_blk_issue_rq(struct mmc_queue *mq, struct request *req)
                 }
 
                 brq.data.sg = mq->sg;
-                brq.data.sg_len = blk_rq_map_sg(req->q, req, brq.data.sg);
+                brq.data.sg_len = mmc_queue_map_sg(mq);
+
+                mmc_queue_bounce_pre(mq);
 
                 if (brq.data.blocks !=
                     (req->nr_sectors >> (md->block_bits - 9))) {
@@ -279,6 +281,9 @@ static int mmc_blk_issue_rq(struct mmc_queue *mq, struct request *req)
                 }
 
                 mmc_wait_for_req(card->host, &brq.mrq);
+
+                mmc_queue_bounce_post(mq);
+
                 if (brq.cmd.error) {
                         printk(KERN_ERR "%s: error %d sending read/write command\n",
                                req->rq_disk->disk_name, brq.cmd.error);