[PATCH 2/5] mmc_block: Add discard support

[Adrian Hunter]

Enable MMC to service discard requests.  In the case of SD
and MMC cards that do not support trim, discards become
erases.  In the case of cards (MMC) that only allow erases
in multiples of erase group size, round to the nearest
completely discarded erase group.

Signed-off-by: Adrian Hunter <adrian.hunter@xxxxxxxxx>
---
 drivers/mmc/card/block.c |   42 +++++++++++++++++++++++++++++++++++++++++-
 drivers/mmc/card/queue.c |   16 ++++++++++++++--
 2 files changed, 55 insertions(+), 3 deletions(-)

diff --git a/drivers/mmc/card/block.c b/drivers/mmc/card/block.c
index cb9fbc8..adb8314 100644
--- a/drivers/mmc/card/block.c
+++ b/drivers/mmc/card/block.c
@@ -242,7 +242,40 @@ static u32 get_card_status(struct mmc_card *card, struct request *req)
 	return cmd.resp[0];
 }
 
-static int mmc_blk_issue_rq(struct mmc_queue *mq, struct request *req)
+static int mmc_blk_issue_discard_rq(struct mmc_queue *mq, struct request *req)
+{
+	struct mmc_blk_data *md = mq->data;
+	struct mmc_card *card = md->queue.card;
+	unsigned int from, nr, arg;
+	int err = 0;
+
+	mmc_claim_host(card->host);
+
+	if (!mmc_can_erase(card)) {
+		err = -EOPNOTSUPP;
+		goto out;
+	}
+
+	from = blk_rq_pos(req);
+	nr = blk_rq_sectors(req);
+
+	if (mmc_can_trim(card))
+		arg = MMC_TRIM_ARG;
+	else
+		arg = MMC_ERASE_ARG;
+
+	err = mmc_erase(card, from, nr, arg);
+out:
+	spin_lock_irq(&md->lock);
+	__blk_end_request(req, err, blk_rq_bytes(req));
+	spin_unlock_irq(&md->lock);
+
+	mmc_release_host(card->host);
+
+	return err ? 0 : 1;
+}
+
+static int mmc_blk_issue_rw_rq(struct mmc_queue *mq, struct request *req)
 {
 	struct mmc_blk_data *md = mq->data;
 	struct mmc_card *card = md->queue.card;
@@ -470,6 +503,13 @@ static int mmc_blk_issue_rq(struct mmc_queue *mq, struct request *req)
 	return 0;
 }
 
+static int mmc_blk_issue_rq(struct mmc_queue *mq, struct request *req)
+{
+	if (req->cmd_flags & REQ_DISCARD)
+		return mmc_blk_issue_discard_rq(mq, req);
+	else
+		return mmc_blk_issue_rw_rq(mq, req);
+}
 
 static inline int mmc_blk_readonly(struct mmc_card *card)
 {
diff --git a/drivers/mmc/card/queue.c b/drivers/mmc/card/queue.c
index ec92bcb..0add067 100644
--- a/drivers/mmc/card/queue.c
+++ b/drivers/mmc/card/queue.c
@@ -30,9 +30,9 @@
 static int mmc_prep_request(struct request_queue *q, struct request *req)
 {
 	/*
-	 * We only like normal block requests.
+	 * We only like normal block requests and discards.
 	 */
-	if (req->cmd_type != REQ_TYPE_FS) {
+	if (req->cmd_type != REQ_TYPE_FS && !(req->cmd_flags & REQ_DISCARD)) {
 		blk_dump_rq_flags(req, "MMC bad request");
 		return BLKPREP_KILL;
 	}
@@ -130,6 +130,18 @@ int mmc_init_queue(struct mmc_queue *mq, struct mmc_card *card, spinlock_t *lock
 	blk_queue_prep_rq(mq->queue, mmc_prep_request);
 	blk_queue_ordered(mq->queue, QUEUE_ORDERED_DRAIN, NULL);
 	queue_flag_set_unlocked(QUEUE_FLAG_NONROT, mq->queue);
+	if (mmc_can_erase(card)) {
+		queue_flag_set_unlocked(QUEUE_FLAG_DISCARD, mq->queue);
+		mq->queue->limits.max_discard_sectors = UINT_MAX;
+		if (card->erased_byte == 0)
+			mq->queue->limits.discard_zeroes_data = 1;
+		if (!mmc_can_trim(card) && is_power_of_2(card->erase_size)) {
+			mq->queue->limits.discard_granularity =
+							card->erase_size << 9;
+			mq->queue->limits.discard_alignment =
+							card->erase_size << 9;
+		}
+	}
 
 #ifdef CONFIG_MMC_BLOCK_BOUNCE
 	if (host->max_hw_segs == 1) {
-- 
1.6.3.3

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