This is a request-for-comments patch. Please provide your feedback.
Allows reliable writes to be used for MMC writes. Reliable writes are used
to service write REQ_FUA/REQ_META requests. Handles both the legacy and the enhanced
reliable write support in MMC cards.
Beyond REQ_FUA/REQ_META, this was meant to be used by a following patch that aimed
to reduce write amplification issues in cards employing a small (usually flash page-sized)
buffer and a large (usually erase-block sized) buffer, at the expense of performance.
Signed-off-by: Andrei Warkentin <andreiw@xxxxxxxxxxxx>
---
drivers/mmc/card/block.c | 85 +++++++++++++++++++++++++++++++++++++++++++--
drivers/mmc/core/mmc.c | 5 +++
include/linux/mmc/card.h | 2 +
include/linux/mmc/mmc.h | 4 ++
4 files changed, 92 insertions(+), 4 deletions(-)
diff --git a/drivers/mmc/card/block.c b/drivers/mmc/card/block.c
index 61d233a..712fe96 100644
--- a/drivers/mmc/card/block.c
+++ b/drivers/mmc/card/block.c
@@ -48,6 +48,10 @@ MODULE_ALIAS("mmc:block");
#endif
#define MODULE_PARAM_PREFIX "mmcblk."
+#define REL_WRITES_SUPPORTED(card) (mmc_card_mmc((card)) && \
+ (((card)->ext_csd.rel_param & EXT_CSD_WR_REL_PARAM_EN) || \
+ ((card)->ext_csd.rel_sectors)))
+
static DEFINE_MUTEX(block_mutex);
/*
@@ -331,6 +335,59 @@ out:
return err ? 0 : 1;
}
+static int mmc_blk_issue_flush(struct mmc_queue *mq, struct request *req)
+{
+ struct mmc_blk_data *md = mq->data;
+
+ /*
+ No-op, only service this because we need REQ_FUA
+ for reliable writes.
+ */
+ spin_lock_irq(&md->lock);
+ __blk_end_request_all(req, 0);
+ spin_unlock_irq(&md->lock);
+
+ return 1;
+}
+
+/*
+ * Reformat current write as a reliable write, supporting
+ * both legacy and the enhanced reliable write MMC cards.
+ * In each transfer we'll handle only as much as a single
+ * reliable write can handle, thus finish the request in
+ * partial completions.
+ */
+static inline int mmc_apply_rel_rw(struct mmc_blk_request *brq,
+ struct mmc_card *card,
+ struct request *req)
+{
+ int err;
+ struct mmc_command set_count;
+
+ if (!(card->ext_csd.rel_param &
+ EXT_CSD_WR_REL_PARAM_EN)) {
+
+ /* Legacy mode imposes restrictions on transfers. */
+ if (!IS_ALIGNED(brq->cmd.arg, card->ext_csd.rel_sectors))
+ brq->data.blocks = 1;
+
+ if (brq->data.blocks > card->ext_csd.rel_sectors)
+ brq->data.blocks = card->ext_csd.rel_sectors;
+ else if (brq->data.blocks != card->ext_csd.rel_sectors)
+ brq->data.blocks = 1;
+ }
+
+ memset(&set_count, 0, sizeof(struct mmc_command));
+ set_count.opcode = MMC_SET_BLOCK_COUNT;
+ set_count.arg = brq->data.blocks | (1 << 31);
+ set_count.flags = MMC_RSP_R1 | MMC_CMD_AC;
+ err = mmc_wait_for_cmd(card->host, &set_count, 0);
+ if (err)
+ printk(KERN_ERR "%s: error %d SET_BLOCK_COUNT\n",
+ req->rq_disk->disk_name, err);
+ return err;
+}
+
static int mmc_blk_issue_rw_rq(struct mmc_queue *mq, struct request *req)
{
struct mmc_blk_data *md = mq->data;
@@ -338,6 +395,15 @@ static int mmc_blk_issue_rw_rq(struct mmc_queue *mq, struct request *req)
struct mmc_blk_request brq;
int ret = 1, disable_multi = 0;
+ /*
+ Reliable writes are used to implement Forced Unit Access and
+ REQ_META accesses, and it's supported only on MMCs.
+ */
+ bool do_rel_wr = ((req->cmd_flags & REQ_FUA) ||
+ (req->cmd_flags & REQ_META)) &&
+ (rq_data_dir(req) == WRITE) &&
+ REL_WRITES_SUPPORTED(card);
+
mmc_claim_host(card->host);
do {
@@ -374,12 +440,14 @@ static int mmc_blk_issue_rw_rq(struct mmc_queue *mq, struct request *req)
if (disable_multi && brq.data.blocks > 1)
brq.data.blocks = 1;
- if (brq.data.blocks > 1) {
+ if (brq.data.blocks > 1 || do_rel_wr) {
/* SPI multiblock writes terminate using a special
- * token, not a STOP_TRANSMISSION request.
+ * token, not a STOP_TRANSMISSION request. Reliable
+ * writes use SET_BLOCK_COUNT and do not use a
+ * STOP_TRANSMISSION request either.
*/
- if (!mmc_host_is_spi(card->host)
- || rq_data_dir(req) == READ)
+ if ((!mmc_host_is_spi(card->host) && !do_rel_wr) ||
+ rq_data_dir(req) == READ)
brq.mrq.stop = &brq.stop;
readcmd = MMC_READ_MULTIPLE_BLOCK;
writecmd = MMC_WRITE_MULTIPLE_BLOCK;
@@ -396,6 +464,11 @@ static int mmc_blk_issue_rw_rq(struct mmc_queue *mq, struct request *req)
brq.data.flags |= MMC_DATA_WRITE;
}
+ if (do_rel_wr) {
+ if (mmc_apply_rel_rw(&brq, card, req))
+ goto cmd_err;
+ }
+
mmc_set_data_timeout(&brq.data, card);
brq.data.sg = mq->sg;
@@ -565,6 +638,8 @@ static int mmc_blk_issue_rq(struct mmc_queue *mq, struct request *req)
return mmc_blk_issue_secdiscard_rq(mq, req);
else
return mmc_blk_issue_discard_rq(mq, req);
+ } else if (req->cmd_flags & REQ_FLUSH) {
+ return mmc_blk_issue_flush(mq, req);
} else {
return mmc_blk_issue_rw_rq(mq, req);
}
@@ -622,6 +697,8 @@ static struct mmc_blk_data *mmc_blk_alloc(struct mmc_card *card)
md->disk->queue = md->queue.queue;
md->disk->driverfs_dev = &card->dev;
set_disk_ro(md->disk, md->read_only);
+ if (REL_WRITES_SUPPORTED(card))
+ blk_queue_flush(md->queue.queue, REQ_FLUSH | REQ_FUA);
/*
* As discussed on lkml, GENHD_FL_REMOVABLE should:
diff --git a/drivers/mmc/core/mmc.c b/drivers/mmc/core/mmc.c
index 14e95f3..1b1e142 100644
--- a/drivers/mmc/core/mmc.c
+++ b/drivers/mmc/core/mmc.c
@@ -299,6 +299,8 @@ static int mmc_read_ext_csd(struct mmc_card *card)
ext_csd[EXT_CSD_ERASE_TIMEOUT_MULT];
card->ext_csd.hc_erase_size =
ext_csd[EXT_CSD_HC_ERASE_GRP_SIZE] << 10;
+
+ card->ext_csd.rel_sectors = ext_csd[EXT_CSD_REL_WR_SEC_C];
}
if (card->ext_csd.rev >= 4) {
@@ -350,6 +352,9 @@ static int mmc_read_ext_csd(struct mmc_card *card)
ext_csd[EXT_CSD_TRIM_MULT];
}
+ if (card->ext_csd.rev >= 5)
+ card->ext_csd.rel_param = ext_csd[EXT_CSD_WR_REL_PARAM];
+
if (ext_csd[EXT_CSD_ERASED_MEM_CONT])
card->erased_byte = 0xFF;
else
diff --git a/include/linux/mmc/card.h b/include/linux/mmc/card.h
index adb4888..959e3d8 100644
--- a/include/linux/mmc/card.h
+++ b/include/linux/mmc/card.h
@@ -45,6 +45,8 @@ struct mmc_ext_csd {
u8 rev;
u8 erase_group_def;
u8 sec_feature_support;
+ u8 rel_sectors;
+ u8 rel_param;
unsigned int sa_timeout; /* Units: 100ns */
unsigned int hs_max_dtr;
unsigned int sectors;
diff --git a/include/linux/mmc/mmc.h b/include/linux/mmc/mmc.h
index 264ba54..44a8157 100644
--- a/include/linux/mmc/mmc.h
+++ b/include/linux/mmc/mmc.h
@@ -255,6 +255,7 @@ struct _mmc_csd {
#define EXT_CSD_PARTITION_ATTRIBUTE 156 /* R/W */
#define EXT_CSD_PARTITION_SUPPORT 160 /* RO */
+#define EXT_CSD_WR_REL_PARAM 166 /* RO */
#define EXT_CSD_ERASE_GROUP_DEF 175 /* R/W */
#define EXT_CSD_ERASED_MEM_CONT 181 /* RO */
#define EXT_CSD_BUS_WIDTH 183 /* R/W */
@@ -264,6 +265,7 @@ struct _mmc_csd {
#define EXT_CSD_CARD_TYPE 196 /* RO */
#define EXT_CSD_SEC_CNT 212 /* RO, 4 bytes */
#define EXT_CSD_S_A_TIMEOUT 217 /* RO */
+#define EXT_CSD_REL_WR_SEC_C 222 /* RO */
#define EXT_CSD_HC_WP_GRP_SIZE 221 /* RO */
#define EXT_CSD_ERASE_TIMEOUT_MULT 223 /* RO */
#define EXT_CSD_HC_ERASE_GRP_SIZE 224 /* RO */
@@ -276,6 +278,8 @@ struct _mmc_csd {
* EXT_CSD field definitions
*/
+#define EXT_CSD_WR_REL_PARAM_EN (1<<2)
+
#define EXT_CSD_CMD_SET_NORMAL (1<<0)
#define EXT_CSD_CMD_SET_SECURE (1<<1)
#define EXT_CSD_CMD_SET_CPSECURE (1<<2)
--
1.7.0.4
--
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