mmc: block: Add error-handling comments

Add error-handling comments to explain what would also be done for blk-mq
if it used the legacy error-handling.

Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Acked-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Tested-by: Linus Walleij <linus.walleij@linaro.org>

diff --git a/drivers/mmc/core/block.c b/drivers/mmc/core/block.c
index e44f6d90aeb4721c6e51a2ea1a2aca5960a9324b..7dcd5d5b203bc8a5c80abed4716d2d83938130fd 100644 (file)
--- a/drivers/mmc/core/block.c
+++ b/drivers/mmc/core/block.c
@@ -1911,7 +1911,11 @@ static void mmc_blk_issue_rw_rq(struct mmc_queue *mq, struct request *new_req)
                case MMC_BLK_SUCCESS:
                case MMC_BLK_PARTIAL:
                        /*
-                        * A block was successfully transferred.
+                        * Reset success, and accept bytes_xfered. For
+                        * MMC_BLK_PARTIAL re-submit the remaining request. For
+                        * MMC_BLK_SUCCESS error out the remaining request (it
+                        * could not be re-submitted anyway if a next request
+                        * had already begun).
                         */
                        mmc_blk_reset_success(md, type);
 
@@ -1931,6 +1935,14 @@ static void mmc_blk_issue_rw_rq(struct mmc_queue *mq, struct request *new_req)
                        }
                        break;
                case MMC_BLK_CMD_ERR:
+                       /*
+                        * For SD cards, get bytes written, but do not accept
+                        * bytes_xfered if that fails. For MMC cards accept
+                        * bytes_xfered. Then try to reset. If reset fails then
+                        * error out the remaining request, otherwise retry
+                        * once (N.B mmc_blk_reset() will not succeed twice in a
+                        * row).
+                        */
                        req_pending = mmc_blk_rw_cmd_err(md, card, brq, old_req, req_pending);
                        if (mmc_blk_reset(md, card->host, type)) {
                                if (req_pending)
@@ -1947,11 +1959,20 @@ static void mmc_blk_issue_rw_rq(struct mmc_queue *mq, struct request *new_req)
                        }
                        break;
                case MMC_BLK_RETRY:
+                       /*
+                        * Do not accept bytes_xfered, but retry up to 5 times,
+                        * otherwise same as abort.
+                        */
                        retune_retry_done = brq->retune_retry_done;
                        if (retry++ < 5)
                                break;
                        /* Fall through */
                case MMC_BLK_ABORT:
+                       /*
+                        * Do not accept bytes_xfered, but try to reset. If
+                        * reset succeeds, try once more, otherwise error out
+                        * the request.
+                        */
                        if (!mmc_blk_reset(md, card->host, type))
                                break;
                        mmc_blk_rw_cmd_abort(mq, card, old_req, mq_rq);
@@ -1960,6 +1981,13 @@ static void mmc_blk_issue_rw_rq(struct mmc_queue *mq, struct request *new_req)
                case MMC_BLK_DATA_ERR: {
                        int err;
 
+                       /*
+                        * Do not accept bytes_xfered, but try to reset. If
+                        * reset succeeds, try once more. If reset fails with
+                        * ENODEV which means the partition is wrong, then error
+                        * out the request. Otherwise attempt to read one sector
+                        * at a time.
+                        */
                        err = mmc_blk_reset(md, card->host, type);
                        if (!err)
                                break;
@@ -1971,6 +1999,10 @@ static void mmc_blk_issue_rw_rq(struct mmc_queue *mq, struct request *new_req)
                        /* Fall through */
                }
                case MMC_BLK_ECC_ERR:
+                       /*
+                        * Do not accept bytes_xfered. If reading more than one
+                        * sector, try reading one sector at a time.
+                        */
                        if (brq->data.blocks > 1) {
                                /* Redo read one sector at a time */
                                pr_warn("%s: retrying using single block read\n",
@@ -1992,10 +2024,12 @@ static void mmc_blk_issue_rw_rq(struct mmc_queue *mq, struct request *new_req)
                        }
                        break;
                case MMC_BLK_NOMEDIUM:
+                       /* Do not accept bytes_xfered. Error out the request */
                        mmc_blk_rw_cmd_abort(mq, card, old_req, mq_rq);
                        mmc_blk_rw_try_restart(mq, new_req, mqrq_cur);
                        return;
                default:
+                       /* Do not accept bytes_xfered. Error out the request */
                        pr_err("%s: Unhandled return value (%d)",
                                        old_req->rq_disk->disk_name, status);
                        mmc_blk_rw_cmd_abort(mq, card, old_req, mq_rq);