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>

3 files changed, 31 insertions, 1 deletions

diff --git a/include/linux/mmc/card.h b/include/linux/mmc/card.h
index 5c69315d60cc..be2500a49925 100644
--- a/include/linux/mmc/card.h
+++ b/include/linux/mmc/card.h
@@ -187,6 +187,18 @@ struct sdio_func_tuple;
 
 #define SDIO_MAX_FUNCS          7
 
+enum mmc_blk_status {
+        MMC_BLK_SUCCESS = 0,
+        MMC_BLK_PARTIAL,
+        MMC_BLK_CMD_ERR,
+        MMC_BLK_RETRY,
+        MMC_BLK_ABORT,
+        MMC_BLK_DATA_ERR,
+        MMC_BLK_ECC_ERR,
+        MMC_BLK_NOMEDIUM,
+        MMC_BLK_NEW_REQUEST,
+};
+
 /* The number of MMC physical partitions.  These consist of:
  * boot partitions (2), general purpose partitions (4) in MMC v4.4.
  */
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;
 
diff --git a/include/linux/mmc/host.h b/include/linux/mmc/host.h
index c89a1bb87fa5..523d570f58ad 100644
--- a/include/linux/mmc/host.h
+++ b/include/linux/mmc/host.h
@@ -170,6 +170,22 @@ struct mmc_slot {
         void *handler_priv;
 };
 
+/**
+ * mmc_context_info - synchronization details for mmc context
+ * @is_done_rcv         wake up reason was done request
+ * @is_new_req          wake up reason was new request
+ * @is_waiting_last_req mmc context waiting for single running request
+ * @wait                wait queue
+ * @lock                lock to protect data fields
+ */
+struct mmc_context_info {
+        bool                    is_done_rcv;
+        bool                    is_new_req;
+        bool                    is_waiting_last_req;
+        wait_queue_head_t       wait;
+        spinlock_t              lock;
+};
+
 struct regulator;
 
 struct mmc_supply {
@@ -331,6 +347,7 @@ struct mmc_host {
         struct dentry           *debugfs_root;
 
         struct mmc_async_req    *areq;          /* active async req */
+        struct mmc_context_info context_info;   /* async synchronization info */
 
 #ifdef CONFIG_FAIL_MMC_REQUEST
         struct fault_attr       fail_mmc_request;