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>
diff --git a/drivers/mmc/card/block.c b/drivers/mmc/card/block.c
index 540ff4b..cbd4b6e 100644
--- a/drivers/mmc/card/block.c
+++ b/drivers/mmc/card/block.c
@@ -262,7 +262,9 @@
}
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 @@
}
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);