mmc_block: add discard support

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@nokia.com>
Acked-by: Jens Axboe <axboe@kernel.dk>
Cc: Kyungmin Park <kmpark@infradead.org>
Cc: Madhusudhan Chikkature <madhu.cr@ti.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Ben Gardiner <bengardiner@nanometrics.ca>
Cc: <linux-mmc@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 14 insertions, 2 deletions

diff --git a/drivers/mmc/card/queue.c b/drivers/mmc/card/queue.c
index c77eb49eda0e..3b15884e435c 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);
         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) {