mmc: fix async request mechanism for sequential read scenarios

When current request is running on the bus and if next request fetched
by mmcqd is NULL, mmc context (mmcqd thread) gets blocked until the
current request completes. This means that if new request comes in while
the mmcqd thread is blocked, this new request can not be prepared in
parallel to current ongoing request. This may result in delaying the new
request execution and increase it's latency.

This change allows to wake up the MMC thread on new request arrival.
Now once the MMC thread is woken up, a new request can be fetched and
prepared in parallel to the current running request which means this new
request can be started immediately after the current running request
completes.

With this change read throughput is improved by 16%.

Signed-off-by: Konstantin Dorfman <kdorfman@codeaurora.org>
Reviewed-by: Seungwon Jeon <tgih.jun@samsung.com>
Signed-off-by: Chris Ball <cjb@laptop.org>

1 files changed, 2 insertions, 1 deletions

diff --git a/include/linux/mmc/core.h b/include/linux/mmc/core.h
index 5bf7c2274fcb..495d1336149c 100644
--- a/include/linux/mmc/core.h
+++ b/include/linux/mmc/core.h
@@ -120,6 +120,7 @@ struct mmc_data {
 	s32			host_cookie;	/* host private data */
 };
 
+struct mmc_host;
 struct mmc_request {
 	struct mmc_command	*sbc;		/* SET_BLOCK_COUNT for multiblock */
 	struct mmc_command	*cmd;
@@ -128,9 +129,9 @@ struct mmc_request {
 
 	struct completion	completion;
 	void			(*done)(struct mmc_request *);/* completion function */
+	struct mmc_host		*host;
 };
 
-struct mmc_host;
 struct mmc_card;
 struct mmc_async_req;