linux-kernel - [PATCH v3 3/4] mmc: host: hsq: Handle an unusual case of returing busy

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Date:   Thu, 19 Mar 2020 18:54:21 +0800
From:   Baolin Wang <baolin.wang7@...il.com>
To:     adrian.hunter@...el.com, ulf.hansson@...aro.org
Cc:     orsonzhai@...il.com, zhang.lyra@...il.com, baolin.wang7@...il.com,
        arnd@...db.de, linux-mmc@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH v3 3/4] mmc: host: hsq: Handle an unusual case of returing busy

There is an unusual case that the card is busy when trying to send a
command, and we can not polling the card status in interrupt context
by using request_atomic() to dispatch requests.

Thus we should queue a work to try again in the non-atomic context
in case the host releases the busy signal later.

Signed-off-by: Baolin Wang <baolin.wang7@...il.com>
---
 drivers/mmc/host/mmc_hsq.c | 37 ++++++++++++++++++++++++++++++++++++-
 drivers/mmc/host/mmc_hsq.h |  1 +
 2 files changed, 37 insertions(+), 1 deletion(-)

diff --git a/drivers/mmc/host/mmc_hsq.c b/drivers/mmc/host/mmc_hsq.c
index fdbaa98..3edad11 100644
--- a/drivers/mmc/host/mmc_hsq.c
+++ b/drivers/mmc/host/mmc_hsq.c
@@ -15,11 +15,33 @@
 #define HSQ_NUM_SLOTS	64
 #define HSQ_INVALID_TAG	HSQ_NUM_SLOTS
 
+static void mmc_hsq_retry_handler(struct work_struct *work)
+{
+	struct mmc_hsq *hsq = container_of(work, struct mmc_hsq, retry_work);
+	struct mmc_host *mmc = hsq->mmc;
+	struct mmc_request *mrq = hsq->mrq;
+	struct mmc_data *data = mrq->data;
+
+	if (mmc->ops->request) {
+		mmc->ops->request(mmc, mrq);
+		return;
+	}
+
+	/*
+	 * If host does not supply the callback in normal context to
+	 * handle request, just finish this request.
+	 */
+	data->error = -EBUSY;
+	data->bytes_xfered = 0;
+	mmc_hsq_finalize_request(mmc, mrq);
+}
+
 static void mmc_hsq_pump_requests(struct mmc_hsq *hsq)
 {
 	struct mmc_host *mmc = hsq->mmc;
 	struct hsq_slot *slot;
 	unsigned long flags;
+	int ret = 0;
 
 	spin_lock_irqsave(&hsq->lock, flags);
 
@@ -42,9 +64,21 @@ static void mmc_hsq_pump_requests(struct mmc_hsq *hsq)
 	spin_unlock_irqrestore(&hsq->lock, flags);
 
 	if (mmc->ops->request_atomic)
-		mmc->ops->request_atomic(mmc, hsq->mrq);
+		ret = mmc->ops->request_atomic(mmc, hsq->mrq);
 	else
 		mmc->ops->request(mmc, hsq->mrq);
+
+	/*
+	 * If returning BUSY from request_atomic(), which means the card
+	 * may be busy now, and we should change to non-atomic context to
+	 * try again for this unusual case, to avoid time-consuming operations
+	 * in the atomic context.
+	 *
+	 * Note: we can ignore other error cases, since the host driver
+	 * will handle them.
+	 */
+	if (ret == -EBUSY)
+		schedule_work(&hsq->retry_work);
 }
 
 static void mmc_hsq_update_next_tag(struct mmc_hsq *hsq, int remains)
@@ -327,6 +361,7 @@ int mmc_hsq_init(struct mmc_hsq *hsq, struct mmc_host *mmc)
 	hsq->mmc->cqe_private = hsq;
 	mmc->cqe_ops = &mmc_hsq_ops;
 
+	INIT_WORK(&hsq->retry_work, mmc_hsq_retry_handler);
 	spin_lock_init(&hsq->lock);
 	init_waitqueue_head(&hsq->wait_queue);
 
diff --git a/drivers/mmc/host/mmc_hsq.h b/drivers/mmc/host/mmc_hsq.h
index d51beb7..81f6c4f 100644
--- a/drivers/mmc/host/mmc_hsq.h
+++ b/drivers/mmc/host/mmc_hsq.h
@@ -12,6 +12,7 @@ struct mmc_hsq {
 	wait_queue_head_t wait_queue;
 	struct hsq_slot *slot;
 	spinlock_t lock;
+	struct work_struct retry_work;
 
 	int next_tag;
 	int num_slots;
-- 
1.9.1