mmc: block: add handling for two parallel block requests in issue_rw_rq

Change mmc_blk_issue_rw_rq() to become asynchronous.
The execution flow looks like this:

* The mmc-queue calls issue_rw_rq(), which sends the request
  to the host and returns back to the mmc-queue.
* The mmc-queue calls issue_rw_rq() again with a new request.
* This new request is prepared in issue_rw_rq(), then it waits for
  the active request to complete before pushing it to the host.
* When the mmc-queue is empty it will call issue_rw_rq() with a NULL
  req to finish off the active request without starting a new request.

Signed-off-by: Per Forlin <per.forlin@linaro.org>
Acked-by: Kyungmin Park <kyungmin.park@samsung.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Venkatraman S <svenkatr@ti.com>
Tested-by: Sourav Poddar <sourav.poddar@ti.com>
Tested-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Chris Ball <cjb@laptop.org>

1 files changed, 12 insertions, 5 deletions

diff --git a/drivers/mmc/card/queue.c b/drivers/mmc/card/queue.c
index a38d310f5030..45fb362e3f01 100644
--- a/drivers/mmc/card/queue.c
+++ b/drivers/mmc/card/queue.c
@@ -52,6 +52,7 @@ static int mmc_queue_thread(void *d)
         down(&mq->thread_sem);
         do {
                 struct request *req = NULL;
+                struct mmc_queue_req *tmp;
 
                 spin_lock_irq(q->queue_lock);
                 set_current_state(TASK_INTERRUPTIBLE);
@@ -59,7 +60,10 @@ static int mmc_queue_thread(void *d)
                 mq->mqrq_cur->req = req;
                 spin_unlock_irq(q->queue_lock);
 
-                if (!req) {
+                if (req || mq->mqrq_prev->req) {
+                        set_current_state(TASK_RUNNING);
+                        mq->issue_fn(mq, req);
+                } else {
                         if (kthread_should_stop()) {
                                 set_current_state(TASK_RUNNING);
                                 break;
@@ -67,11 +71,14 @@ static int mmc_queue_thread(void *d)
                         up(&mq->thread_sem);
                         schedule();
                         down(&mq->thread_sem);
-                        continue;
                 }
-                set_current_state(TASK_RUNNING);
 
-                mq->issue_fn(mq, req);
+                /* Current request becomes previous request and vice versa. */
+                mq->mqrq_prev->brq.mrq.data = NULL;
+                mq->mqrq_prev->req = NULL;
+                tmp = mq->mqrq_prev;
+                mq->mqrq_prev = mq->mqrq_cur;
+                mq->mqrq_cur = tmp;
         } while (1);
         up(&mq->thread_sem);
 
@@ -97,7 +104,7 @@ static void mmc_request(struct request_queue *q)
                 return;
         }
 
-        if (!mq->mqrq_cur->req)
+        if (!mq->mqrq_cur->req && !mq->mqrq_prev->req)
                 wake_up_process(mq->thread);
 }