mmc_block: ensure all sectors that do not have errors are read

If a card encounters an ECC error while reading a sector it will
timeout.  Instead of reporting the entire I/O request as having
an error, redo the I/O one sector at a time so that all readable
sectors are provided to the upper layers.

Signed-off-by: Adrian Hunter <ext-adrian.hunter@nokia.com>
Signed-off-by: Pierre Ossman <drzeus@drzeus.cx>

1 files changed, 59 insertions, 17 deletions

diff --git a/drivers/mmc/card/block.c b/drivers/mmc/card/block.c
index cc9b3abf4a3f..45b1f430685f 100644
--- a/drivers/mmc/card/block.c
+++ b/drivers/mmc/card/block.c
@@ -229,7 +229,7 @@ static int mmc_blk_issue_rq(struct mmc_queue *mq, struct request *req)
         struct mmc_blk_data *md = mq->data;
         struct mmc_card *card = md->queue.card;
         struct mmc_blk_request brq;
-        int ret = 1;
+        int ret = 1, disable_multi = 0;
 
         mmc_claim_host(card->host);
 
@@ -251,6 +251,14 @@ static int mmc_blk_issue_rq(struct mmc_queue *mq, struct request *req)
                 brq.stop.flags = MMC_RSP_SPI_R1B | MMC_RSP_R1B | MMC_CMD_AC;
                 brq.data.blocks = req->nr_sectors;
 
+                /*
+                 * After a read error, we redo the request one sector at a time
+                 * in order to accurately determine which sectors can be read
+                 * successfully.
+                 */
+                if (disable_multi && brq.data.blocks > 1)
+                        brq.data.blocks = 1;
+
                 if (brq.data.blocks > 1) {
                         /* SPI multiblock writes terminate using a special
                          * token, not a STOP_TRANSMISSION request.
@@ -279,6 +287,25 @@ static int mmc_blk_issue_rq(struct mmc_queue *mq, struct request *req)
                 brq.data.sg = mq->sg;
                 brq.data.sg_len = mmc_queue_map_sg(mq);
 
+                /*
+                 * Adjust the sg list so it is the same size as the
+                 * request.
+                 */
+                if (brq.data.blocks != req->nr_sectors) {
+                        int i, data_size = brq.data.blocks << 9;
+                        struct scatterlist *sg;
+
+                        for_each_sg(brq.data.sg, sg, brq.data.sg_len, i) {
+                                data_size -= sg->length;
+                                if (data_size <= 0) {
+                                        sg->length += data_size;
+                                        i++;
+                                        break;
+                                }
+                        }
+                        brq.data.sg_len = i;
+                }
+
                 mmc_queue_bounce_pre(mq);
 
                 mmc_wait_for_req(card->host, &brq.mrq);
@@ -290,8 +317,16 @@ static int mmc_blk_issue_rq(struct mmc_queue *mq, struct request *req)
                  * until later as we need to wait for the card to leave
                  * programming mode even when things go wrong.
                  */
-                if (brq.cmd.error || brq.data.error || brq.stop.error)
+                if (brq.cmd.error || brq.data.error || brq.stop.error) {
+                        if (brq.data.blocks > 1 && rq_data_dir(req) == READ) {
+                                /* Redo read one sector at a time */
+                                printk(KERN_WARNING "%s: retrying using single "
+                                       "block read\n", req->rq_disk->disk_name);
+                                disable_multi = 1;
+                                continue;
+                        }
                         status = get_card_status(card, req);
+                }
 
                 if (brq.cmd.error) {
                         printk(KERN_ERR "%s: error %d sending read/write "
@@ -348,8 +383,20 @@ static int mmc_blk_issue_rq(struct mmc_queue *mq, struct request *req)
 #endif
                 }
 
-                if (brq.cmd.error || brq.data.error || brq.stop.error)
+                if (brq.cmd.error || brq.stop.error || brq.data.error) {
+                        if (rq_data_dir(req) == READ) {
+                                /*
+                                 * After an error, we redo I/O one sector at a
+                                 * time, so we only reach here after trying to
+                                 * read a single sector.
+                                 */
+                                spin_lock_irq(&md->lock);
+                                ret = __blk_end_request(req, -EIO, brq.data.blksz);
+                                spin_unlock_irq(&md->lock);
+                                continue;
+                        }
                         goto cmd_err;
+                }
 
                 /*
                  * A block was successfully transferred.
@@ -371,25 +418,20 @@ static int mmc_blk_issue_rq(struct mmc_queue *mq, struct request *req)
          * If the card is not SD, we can still ok written sectors
          * 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) {
-                if (mmc_card_sd(card)) {
-                        u32 blocks;
+        if (mmc_card_sd(card)) {
+                u32 blocks;
 
-                        blocks = mmc_sd_num_wr_blocks(card);
-                        if (blocks != (u32)-1) {
-                                spin_lock_irq(&md->lock);
-                                ret = __blk_end_request(req, 0, blocks << 9);
-                                spin_unlock_irq(&md->lock);
-                        }
-                } else {
+                blocks = mmc_sd_num_wr_blocks(card);
+                if (blocks != (u32)-1) {
                         spin_lock_irq(&md->lock);
-                        ret = __blk_end_request(req, 0, brq.data.bytes_xfered);
+                        ret = __blk_end_request(req, 0, blocks << 9);
                         spin_unlock_irq(&md->lock);
                 }
+        } else {
+                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);