mmc: remove multiwrite capability

Relax requirements on host controllers and only require that they do not
report a transfer count than is larger than the actual one (i.e. a lower
value is okay). This is how many other parts of the kernel behaves so
upper layers should already be prepared to handle that scenario. This
gives us a performance boost on MMC cards.

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

1 files changed, 19 insertions, 28 deletions

diff --git a/drivers/mmc/card/block.c b/drivers/mmc/card/block.c
index 4b0f8220f15..66e5a5487c2 100644
--- a/drivers/mmc/card/block.c
+++ b/drivers/mmc/card/block.c
@@ -237,17 +237,6 @@ static int mmc_blk_issue_rq(struct mmc_queue *mq, struct request *req)
                 if (brq.data.blocks > card->host->max_blk_count)
                         brq.data.blocks = card->host->max_blk_count;
 
-                /*
-                 * If the host doesn't support multiple block writes, force
-                 * block writes to single block. SD cards are excepted from
-                 * this rule as they support querying the number of
-                 * successfully written sectors.
-                 */
-                if (rq_data_dir(req) != READ &&
-                    !(card->host->caps & MMC_CAP_MULTIWRITE) &&
-                    !mmc_card_sd(card))
-                        brq.data.blocks = 1;
-
                 if (brq.data.blocks > 1) {
                         /* SPI multiblock writes terminate using a special
                          * token, not a STOP_TRANSMISSION request.
@@ -367,30 +356,32 @@ static int mmc_blk_issue_rq(struct mmc_queue *mq, struct request *req)
          * mark the known good sectors as ok.
          *
          * If the card is not SD, we can still ok written sectors
-         * if the controller can do proper error reporting.
+         * as reported by the controller (which might be less than
+         * the real number of written sectors, but never more).
          *
          * For reads we just fail the entire chunk as that should
          * be safe in all cases.
          */
-        if (rq_data_dir(req) != READ && mmc_card_sd(card)) {
-                u32 blocks;
-                unsigned int bytes;
-
-                blocks = mmc_sd_num_wr_blocks(card);
-                if (blocks != (u32)-1) {
-                        if (card->csd.write_partial)
-                                bytes = blocks << md->block_bits;
-                        else
-                                bytes = blocks << 9;
+        if (rq_data_dir(req) != READ) {
+                if (mmc_card_sd(card)) {
+                        u32 blocks;
+                        unsigned int bytes;
+
+                        blocks = mmc_sd_num_wr_blocks(card);
+                        if (blocks != (u32)-1) {
+                                if (card->csd.write_partial)
+                                        bytes = blocks << md->block_bits;
+                                else
+                                        bytes = blocks << 9;
+                                spin_lock_irq(&md->lock);
+                                ret = __blk_end_request(req, 0, bytes);
+                                spin_unlock_irq(&md->lock);
+                        }
+                } else {
                         spin_lock_irq(&md->lock);
-                        ret = __blk_end_request(req, 0, bytes);
+                        ret = __blk_end_request(req, 0, brq.data.bytes_xfered);
                         spin_unlock_irq(&md->lock);
                 }
-        } else if (rq_data_dir(req) != READ &&
-                   (card->host->caps & MMC_CAP_MULTIWRITE)) {
-                spin_lock_irq(&md->lock);
-                ret = __blk_end_request(req, 0, brq.data.bytes_xfered);
-                spin_unlock_irq(&md->lock);
         }
 
         mmc_release_host(card->host);