[PATCH] mmc: block: Support Host to control FUA.

[Wenchao Chen]

From: Wenchao Chen <wenchao.chen@xxxxxxxxxx>

This patch introduces host->fua_disable for MMC host controller.
The host can turn off FUA to improve performance.

1. fua_disable = 1
/sys/block/mmcblk0/queue # cat fua 0
I tested 5 times for each case and output a average speed.

1) Sequential read:
Speed: 266.8MiB/s, 265.1MiB/s, 262.9MiB/s, 268.7MiB/s, 265.2MiB/s
Average speed: 265.74MiB/s

2) Random read:
Speed: 98.75MiB/s, 98.7MiB/s, 98.5MiB/s, 99.4MiB/s, 98.7MiB/s
Average speed: 98.81MiB/s

3) Sequential write:
Speed: 199.94MiB/s, 199.1MiB/s, 205.5MiB/s, 206.5MiB/s, 191.5MiB/s
Average speed: 200.5MiB/s

4) Random write:
Speed: 68.6MiB/s, 71.8MiB/s, 77.1MiB/s, 64.8MiB/s, 69.3MiB/s
Average speed: 70.32MiB/s

2. fua_disable = 0 (default 0)
/sys/block/mmcblk0/queue # cat fua 1
I tested 5 times for each case and output a average speed.

1) Sequential read:
Speed: 259.3MiB/s, 258.8MiB/s, 258.2MiB/s, 259.5MiB/s, 253.5MiB/s
Average speed: 257.86MiB/s

2) Random read:
Speed: 98.9MiB/s, 101MiB/s, 101MiB/s, 99MiB/s, 101.1MiB/s
Average speed: 100.2MiB/s

3) Sequential write:
Speed: 153.7MiB/s, 146.2MiB/s, 151.2MiB/s, 148.8MiB/s, 147.5MiB/s
Average speed: 149.48MiB/s

4) Random write:
Speed: 12.9MiB/s, 12.3MiB/s, 12.6MiB/s, 12.8MiB/s, 12.8MiB/s
Average speed: 12.68MiB/s

According to the above data, disable FUA (fua_disable = 1) improves the
performance. Therefore, it is recommended to support the host to control
FUA.

Signed-off-by: Wenchao Chen <wenchao.chen@xxxxxxxxxx>
---
 drivers/mmc/core/block.c | 3 ++-
 include/linux/mmc/host.h | 3 +++
 2 files changed, 5 insertions(+), 1 deletion(-)

diff --git a/drivers/mmc/core/block.c b/drivers/mmc/core/block.c
index 54cd009aee50..333e819e077a 100644
--- a/drivers/mmc/core/block.c
+++ b/drivers/mmc/core/block.c
@@ -2490,7 +2490,8 @@ static struct mmc_blk_data *mmc_blk_alloc_req(struct mmc_card *card,
 	    ((card->ext_csd.rel_param & EXT_CSD_WR_REL_PARAM_EN) ||
 	     card->ext_csd.rel_sectors)) {
 		md->flags |= MMC_BLK_REL_WR;
-		fua_enabled = true;
+		if (!card->host->fua_disable)
+			fua_enabled = true;
 		cache_enabled = true;
 	}
 	if (mmc_cache_enabled(card->host))
diff --git a/include/linux/mmc/host.h b/include/linux/mmc/host.h
index 8fdd3cf971a3..16a5bee3eeae 100644
--- a/include/linux/mmc/host.h
+++ b/include/linux/mmc/host.h
@@ -517,6 +517,9 @@ struct mmc_host {
 	struct blk_crypto_profile crypto_profile;
 #endif
 
+	/* Host FUA support */
+	bool			fua_disable;
+
 	/* Host Software Queue support */
 	bool			hsq_enabled;
 
-- 
2.17.1