Message-Id: <1356357068-31807-2-git-send-email-merez@codeaurora.org>
Date:	Mon, 24 Dec 2012 15:51:07 +0200
From:	Maya Erez <merez@...eaurora.org>
To:	linux-mmc@...r.kernel.org
Cc:	linux-arm-msm@...r.kernel.org, Maya Erez <merez@...eaurora.org>,
	linux-kernel@...r.kernel.org (open list)
Subject: [PATCH v4 1/2] mmc: core: Add support for idle time BKOPS

Devices have various maintenance operations need to perform internally.
In order to reduce latencies during time critical operations like read
and write, it is better to execute maintenance operations in other
times - when the host is not being serviced. Such operations are called
Background operations (BKOPS).
The device notifies the status of the BKOPS need by updating BKOPS_STATUS
(EXT_CSD byte [246]).

According to the standard a host that supports BKOPS shall check the
status periodically and start background operations as needed, so that
the device has enough time for its maintenance operations.

This patch adds support for this periodic check of the BKOPS status.
Since foreground operations are of higher priority than background
operations the host will check the need for BKOPS when it is idle,
and in case of an incoming request the BKOPS operation will be
interrupted.

When the mmcqd thread is idle, a delayed work is created to check the
need for BKOPS. The time to start the delayed work can be set by the host
controller. If this time is not set, a default time is used.
If the card raised an exception, the need for urgent BKOPS (level 2/3)
will be checked immediately and if needed, the BKOPS will be performed
without waiting for the next idle time.

Signed-off-by: Maya Erez <merez@...eaurora.org>

diff --git a/drivers/mmc/card/block.c b/drivers/mmc/card/block.c
index 21056b9..64bbf75 100644
--- a/drivers/mmc/card/block.c
+++ b/drivers/mmc/card/block.c
@@ -1473,9 +1473,15 @@ static int mmc_blk_issue_rq(struct mmc_queue *mq, struct request *req)
 	struct mmc_blk_data *md = mq->data;
 	struct mmc_card *card = md->queue.card;
 
-	if (req && !mq->mqrq_prev->req)
+	if (req && !mq->mqrq_prev->req) {
 		/* claim host only for the first request */
 		mmc_claim_host(card->host);
+		if (card->ext_csd.bkops_en &&
+		    card->bkops_info.started_delayed_bkops) {
+			card->bkops_info.started_delayed_bkops = false;
+			mmc_stop_bkops(card);
+		}
+	}
 
 	ret = mmc_blk_part_switch(card, md);
 	if (ret) {
diff --git a/drivers/mmc/card/queue.c b/drivers/mmc/card/queue.c
index fadf52e..9d0c96a 100644
--- a/drivers/mmc/card/queue.c
+++ b/drivers/mmc/card/queue.c
@@ -51,6 +51,7 @@ static int mmc_queue_thread(void *d)
 {
 	struct mmc_queue *mq = d;
 	struct request_queue *q = mq->queue;
+	struct mmc_card *card = mq->card;
 
 	current->flags |= PF_MEMALLOC;
 
@@ -83,6 +84,7 @@ static int mmc_queue_thread(void *d)
 				set_current_state(TASK_RUNNING);
 				break;
 			}
+			mmc_start_delayed_bkops(card);
 			up(&mq->thread_sem);
 			schedule();
 			down(&mq->thread_sem);
diff --git a/drivers/mmc/core/core.c b/drivers/mmc/core/core.c
index aaed768..36cef94 100644
--- a/drivers/mmc/core/core.c
+++ b/drivers/mmc/core/core.c
@@ -256,6 +256,33 @@ mmc_start_request(struct mmc_host *host, struct mmc_request *mrq)
 }
 
 /**
+ * mmc_start_delayed_bkops() - Start a delayed work to check for
+ *      the need of non urgent BKOPS
+ *
+ * @card: MMC card to start BKOPS on
+ */
+void mmc_start_delayed_bkops(struct mmc_card *card)
+{
+	if (!card || !card->ext_csd.bkops_en || mmc_card_doing_bkops(card))
+		return;
+
+	pr_debug("%s: %s: queueing delayed_bkops_work\n",
+		 mmc_hostname(card->host), __func__);
+
+	/*
+	 * cancel_delayed_bkops_work will prevent a race condition between
+	 * fetching a request by the mmcqd and the delayed work, in case
+	 * it was removed from the queue work but not started yet
+	 */
+	card->bkops_info.cancel_delayed_work = false;
+	card->bkops_info.started_delayed_bkops = true;
+	queue_delayed_work(system_nrt_wq, &card->bkops_info.dw,
+			   msecs_to_jiffies(
+				   card->bkops_info.delay_ms));
+}
+EXPORT_SYMBOL(mmc_start_delayed_bkops);
+
+/**
  *	mmc_start_bkops - start BKOPS for supported cards
  *	@card: MMC card to start BKOPS
  *	@form_exception: A flag to indicate if this function was
@@ -272,25 +299,47 @@ void mmc_start_bkops(struct mmc_card *card, bool from_exception)
 	bool use_busy_signal;
 
 	BUG_ON(!card);
-
-	if (!card->ext_csd.bkops_en || mmc_card_doing_bkops(card))
+	if (!card->ext_csd.bkops_en)
 		return;
 
+	mmc_claim_host(card->host);
+
+	if ((card->bkops_info.cancel_delayed_work) && !from_exception) {
+		pr_debug("%s: %s: cancel_delayed_work was set, exit\n",
+			 mmc_hostname(card->host), __func__);
+		card->bkops_info.cancel_delayed_work = false;
+		goto out;
+	}
+
+	if (mmc_card_doing_bkops(card)) {
+		pr_debug("%s: %s: already doing bkops, exit\n",
+			 mmc_hostname(card->host), __func__);
+		goto out;
+	}
+
 	err = mmc_read_bkops_status(card);
 	if (err) {
 		pr_err("%s: Failed to read bkops status: %d\n",
 		       mmc_hostname(card->host), err);
-		return;
+		goto out;
 	}
 
 	if (!card->ext_csd.raw_bkops_status)
-		return;
+		goto out;
+
+	pr_info("%s: %s: card->ext_csd.raw_bkops_status = 0x%x\n",
+		mmc_hostname(card->host), __func__,
+		card->ext_csd.raw_bkops_status);
 
+	/*
+	 * If the function was called due to exception but there is no need
+	 * for urgent BKOPS, BKOPs will be performed by the delayed BKOPs
+	 * work, before going to suspend
+	 */
 	if (card->ext_csd.raw_bkops_status < EXT_CSD_BKOPS_LEVEL_2 &&
 	    from_exception)
-		return;
+		goto out;
 
-	mmc_claim_host(card->host);
 	if (card->ext_csd.raw_bkops_status >= EXT_CSD_BKOPS_LEVEL_2) {
 		timeout = MMC_BKOPS_MAX_TIMEOUT;
 		use_busy_signal = true;
@@ -319,6 +368,27 @@ out:
 }
 EXPORT_SYMBOL(mmc_start_bkops);
 
+/**
+ * mmc_start_idle_time_bkops() - check if a non urgent BKOPS is
+ * needed
+ * @work:	The idle time BKOPS work
+ */
+void mmc_start_idle_time_bkops(struct work_struct *work)
+{
+	struct mmc_card *card = container_of(work, struct mmc_card,
+			bkops_info.dw.work);
+
+	/*
+	 * Prevent a race condition between mmc_stop_bkops and the delayed
+	 * BKOPS work in case the delayed work is executed on another CPU
+	 */
+	if (card->bkops_info.cancel_delayed_work)
+		return;
+
+	mmc_start_bkops(card, false);
+}
+EXPORT_SYMBOL(mmc_start_idle_time_bkops);
+
 static void mmc_wait_done(struct mmc_request *mrq)
 {
 	complete(&mrq->completion);
@@ -585,6 +655,17 @@ int mmc_stop_bkops(struct mmc_card *card)
 	int err = 0;
 
 	BUG_ON(!card);
+
+	/*
+	 * Notify the delayed work to be cancelled, in case it was already
+	 * removed from the queue, but was not started yet
+	 */
+	card->bkops_info.cancel_delayed_work = true;
+	if (delayed_work_pending(&card->bkops_info.dw))
+		cancel_delayed_work_sync(&card->bkops_info.dw);
+	if (!mmc_card_doing_bkops(card))
+		goto out;
+
 	err = mmc_interrupt_hpi(card);
 
 	/*
@@ -596,6 +677,7 @@ int mmc_stop_bkops(struct mmc_card *card)
 		err = 0;
 	}
 
+out:
 	return err;
 }
 EXPORT_SYMBOL(mmc_stop_bkops);
@@ -2536,15 +2618,15 @@ int mmc_pm_notify(struct notifier_block *notify_block,
 	switch (mode) {
 	case PM_HIBERNATION_PREPARE:
 	case PM_SUSPEND_PREPARE:
-		if (host->card && mmc_card_mmc(host->card) &&
-		    mmc_card_doing_bkops(host->card)) {
+		if (host->card && mmc_card_mmc(host->card)) {
+			mmc_claim_host(host);
 			err = mmc_stop_bkops(host->card);
+			mmc_release_host(host);
 			if (err) {
 				pr_err("%s: didn't stop bkops\n",
 					mmc_hostname(host));
 				return err;
 			}
-			mmc_card_clr_doing_bkops(host->card);
 		}
 
 		spin_lock_irqsave(&host->lock, flags);
diff --git a/drivers/mmc/core/mmc.c b/drivers/mmc/core/mmc.c
index e6e3911..f68624a 100644
--- a/drivers/mmc/core/mmc.c
+++ b/drivers/mmc/core/mmc.c
@@ -1275,6 +1275,26 @@ static int mmc_init_card(struct mmc_host *host, u32 ocr,
 		}
 	}
 
+	if (!oldcard) {
+		if (card->ext_csd.bkops_en) {
+			INIT_DELAYED_WORK(&card->bkops_info.dw,
+					  mmc_start_idle_time_bkops);
+
+			/*
+			 * Calculate the time to start the BKOPs checking.
+			 * The host controller can set this time in order to
+			 * prevent a race condition before starting BKOPs
+			 * and going into suspend.
+			 * If the host controller didn't set this time,
+			 * a default value is used.
+			 */
+			card->bkops_info.delay_ms = MMC_IDLE_BKOPS_TIME_MS;
+			if (card->bkops_info.host_delay_ms)
+				card->bkops_info.delay_ms =
+					card->bkops_info.host_delay_ms;
+		}
+	}
+
 	if (!oldcard)
 		host->card = card;
 
diff --git a/include/linux/mmc/card.h b/include/linux/mmc/card.h
index 5c69315..ca4cf19 100644
--- a/include/linux/mmc/card.h
+++ b/include/linux/mmc/card.h
@@ -210,6 +210,30 @@ struct mmc_part {
 #define MMC_BLK_DATA_AREA_RPMB	(1<<3)
 };
 
+/**
+ * struct mmc_bkops_info - BKOPS data
+ * @dw:	Idle time bkops delayed work
+ * @host_delay_ms:	The host controller time to start bkops
+ * @delay_ms:	The time to start the BKOPS
+ *        delayed work once MMC thread is idle
+ * @cancel_delayed_work: A flag to indicate if the delayed work
+ *        should be cancelled
+ * @started_delayed_bkops:  A flag to indicate if the delayed
+ *        work was scheduled
+ */
+struct mmc_bkops_info {
+	struct delayed_work	dw;
+	unsigned int		host_delay_ms;
+	unsigned int		delay_ms;
+/*
+ * A default time for checking the need for non urgent BKOPS once mmcqd
+ * is idle.
+ */
+#define MMC_IDLE_BKOPS_TIME_MS 2000
+	bool			cancel_delayed_work;
+	bool			started_delayed_bkops;
+};
+
 /*
  * MMC device
  */
@@ -278,6 +302,8 @@ struct mmc_card {
 	struct dentry		*debugfs_root;
 	struct mmc_part	part[MMC_NUM_PHY_PARTITION]; /* physical partitions */
 	unsigned int    nr_parts;
+
+	struct mmc_bkops_info	bkops_info;
 };
 
 /*
diff --git a/include/linux/mmc/core.h b/include/linux/mmc/core.h
index 5bf7c22..c6426c6 100644
--- a/include/linux/mmc/core.h
+++ b/include/linux/mmc/core.h
@@ -145,6 +145,8 @@ extern int mmc_app_cmd(struct mmc_host *, struct mmc_card *);
 extern int mmc_wait_for_app_cmd(struct mmc_host *, struct mmc_card *,
 	struct mmc_command *, int);
 extern void mmc_start_bkops(struct mmc_card *card, bool from_exception);
+extern void mmc_start_delayed_bkops(struct mmc_card *card);
+extern void mmc_start_idle_time_bkops(struct work_struct *work);
 extern int __mmc_switch(struct mmc_card *, u8, u8, u8, unsigned int, bool);
 extern int mmc_switch(struct mmc_card *, u8, u8, u8, unsigned int);
 
-- 
1.7.3.3
-- 
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of Code Aurora Forum, hosted by The Linux Foundation
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