[PATCH v2 2/2] mmc: block: use single block write in retry

[Bin Liu <b-liu@ti.com>]

Due to errata i2493[0], multi-block write would still fail in retries.

With i2493, the MMC interface has the potential of write failures when
issuing multi-block writes operating in HS200 mode with excessive IO
supply noise.

While the errata provides guidance in hardware design and layout to
minimize the IO supply noise, in theory the write failure cannot be
resolved in hardware. The software solution to ensure the data integrity
is to add minimum 5us delay between block writes. Single-block write is
the practical way to introduce the delay.

This patch reuses recovery_mode flag, and switches to single-block
write in retry when multi-block write fails. It covers both CQE and
non-CQE cases.

[0] https://www.ti.com/lit/pdf/sprz582
Signed-off-by: Bin Liu <b-liu@ti.com>
---
v2: add errata details in the commit message.

 drivers/mmc/core/block.c | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/drivers/mmc/core/block.c b/drivers/mmc/core/block.c
index 05ee76cb0a08..00016584d70d 100644
--- a/drivers/mmc/core/block.c
+++ b/drivers/mmc/core/block.c
@@ -1401,6 +1401,9 @@ static void mmc_blk_data_prep(struct mmc_queue *mq, struct mmc_queue_req *mqrq,
 		    rq_data_dir(req) == WRITE &&
 		    (md->flags & MMC_BLK_REL_WR);
 
+	if (req->rq_flags & RQF_XFER_SINGLE_BLK)
+		recovery_mode = 1;
+
 	memset(brq, 0, sizeof(struct mmc_blk_request));
 
 	mmc_crypto_prepare_req(mqrq);
@@ -1540,10 +1543,13 @@ static void mmc_blk_cqe_complete_rq(struct mmc_queue *mq, struct request *req)
 		err = 0;
 
 	if (err) {
-		if (mqrq->retries++ < MMC_CQE_RETRIES)
+		if (mqrq->retries++ < MMC_CQE_RETRIES) {
+			if (rq_data_dir(req) == WRITE)
+				req->rq_flags |= RQF_XFER_SINGLE_BLK;
 			blk_mq_requeue_request(req, true);
-		else
+		} else {
 			blk_mq_end_request(req, BLK_STS_IOERR);
+		}
 	} else if (mrq->data) {
 		if (blk_update_request(req, BLK_STS_OK, mrq->data->bytes_xfered))
 			blk_mq_requeue_request(req, true);
@@ -2085,6 +2091,8 @@ static void mmc_blk_mq_complete_rq(struct mmc_queue *mq, struct request *req)
 	} else if (!blk_rq_bytes(req)) {
 		__blk_mq_end_request(req, BLK_STS_IOERR);
 	} else if (mqrq->retries++ < MMC_MAX_RETRIES) {
+		if (rq_data_dir(req) == WRITE)
+			req->rq_flags |= RQF_XFER_SINGLE_BLK;
 		blk_mq_requeue_request(req, true);
 	} else {
 		if (mmc_card_removed(mq->card))
-- 
2.34.1