Re: [PATCH 3/3] mmc: block: Enable runtime pm for mmc blkdevice

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On 3/1/2013 6:17 PM, Ulf Hansson wrote:
From: Ulf Hansson <ulf.hansson@xxxxxxxxxx>

Once the mmc blkdevice is being probed, runtime pm will be enabled.
By using runtime autosuspend, the power save operations can be done
when request inactivity occurs for a certain time. Right now the
selected timeout value is set to 3 s.

Moreover, when the blk device is being suspended, we make sure the device
will be runtime resumed. The reason for doing this is that we what the
host suspend sequence to be unaware of any runtime power save operations,
so it can just handle the suspend as the device is fully powerered from a
runtime perspective.

This patch is preparing to make it possible to move BKOPS handling into
the runtime callbacks for the mmc bus_ops. Thus IDLE BKOPS can be
accomplished.

Signed-off-by: Ulf Hansson <ulf.hansson@xxxxxxxxxx>
---
  drivers/mmc/card/block.c |   28 ++++++++++++++++++++++++++--
  1 file changed, 26 insertions(+), 2 deletions(-)

diff --git a/drivers/mmc/card/block.c b/drivers/mmc/card/block.c
index 5bab73b..89d1c39 100644
--- a/drivers/mmc/card/block.c
+++ b/drivers/mmc/card/block.c
@@ -34,6 +34,7 @@
  #include <linux/delay.h>
  #include <linux/capability.h>
  #include <linux/compat.h>
+#include <linux/pm_runtime.h>
#include <linux/mmc/ioctl.h>
  #include <linux/mmc/card.h>
@@ -222,6 +223,7 @@ static ssize_t power_ro_lock_store(struct device *dev,
  	md = mmc_blk_get(dev_to_disk(dev));
  	card = md->queue.card;
+ pm_runtime_get_sync(&card->dev);
  	mmc_claim_host(card->host);
ret = mmc_switch(card, EXT_CSD_CMD_SET_NORMAL, EXT_CSD_BOOT_WP,
@@ -234,6 +236,8 @@ static ssize_t power_ro_lock_store(struct device *dev,
  		card->ext_csd.boot_ro_lock |= EXT_CSD_BOOT_WP_B_PWR_WP_EN;
mmc_release_host(card->host);
+	pm_runtime_mark_last_busy(&card->dev);
+	pm_runtime_put_autosuspend(&card->dev);
if (!ret) {
  		pr_info("%s: Locking boot partition ro until next power on\n",
@@ -492,6 +496,7 @@ static int mmc_blk_ioctl_cmd(struct block_device *bdev,
mrq.cmd = &cmd; + pm_runtime_get_sync(&card->dev);
  	mmc_claim_host(card->host);
err = mmc_blk_part_switch(card, md);
@@ -560,6 +565,8 @@ static int mmc_blk_ioctl_cmd(struct block_device *bdev,
cmd_rel_host:
  	mmc_release_host(card->host);
+	pm_runtime_mark_last_busy(&card->dev);
+	pm_runtime_put_autosuspend(&card->dev);
cmd_done:
  	mmc_blk_put(md);
@@ -1894,9 +1901,11 @@ static int mmc_blk_issue_rq(struct mmc_queue *mq, struct request *req)
  	struct mmc_host *host = card->host;
  	unsigned long flags;
- if (req && !mq->mqrq_prev->req)
+	if (req && !mq->mqrq_prev->req) {
+		pm_runtime_get_sync(&card->dev);
  		/* claim host only for the first request */
  		mmc_claim_host(card->host);
+	}
ret = mmc_blk_part_switch(card, md);
  	if (ret) {
@@ -1932,9 +1941,13 @@ static int mmc_blk_issue_rq(struct mmc_queue *mq, struct request *req)
  	}
out:
-	if (!req && !(mq->flags & MMC_QUEUE_NEW_REQUEST))
+	if (!req && !(mq->flags & MMC_QUEUE_NEW_REQUEST)) {
  		/* release host only when there are no more requests */
  		mmc_release_host(card->host);
+		pm_runtime_mark_last_busy(&card->dev);
+		pm_runtime_put_autosuspend(&card->dev);
+	}
+
  	return ret;
  }
@@ -2331,6 +2344,12 @@ static int mmc_blk_probe(struct mmc_card *card)
  		if (mmc_add_disk(part_md))
  			goto out;
  	}
+
+	pm_runtime_set_active(&card->dev);
+	pm_runtime_set_autosuspend_delay(&card->dev, 3000);
+	pm_runtime_use_autosuspend(&card->dev);
+	pm_runtime_enable(&card->dev);
+
  	return 0;
out:
@@ -2344,9 +2363,12 @@ static void mmc_blk_remove(struct mmc_card *card)
  	struct mmc_blk_data *md = mmc_get_drvdata(card);
mmc_blk_remove_parts(card, md);
+	pm_runtime_get_sync(&card->dev);
  	mmc_claim_host(card->host);
  	mmc_blk_part_switch(card, md);
  	mmc_release_host(card->host);
+	pm_runtime_disable(&card->dev);
+	pm_runtime_put_noidle(&card->dev);
  	mmc_blk_remove_req(md);
  	mmc_set_drvdata(card, NULL);
  }
@@ -2358,6 +2380,7 @@ static int mmc_blk_suspend(struct mmc_card *card)
  	struct mmc_blk_data *md = mmc_get_drvdata(card);
if (md) {
+		pm_runtime_get_sync(&card->dev);
  		mmc_queue_suspend(&md->queue);
  		list_for_each_entry(part_md, &md->part, part) {
  			mmc_queue_suspend(&part_md->queue);
@@ -2381,6 +2404,7 @@ static int mmc_blk_resume(struct mmc_card *card)
  		list_for_each_entry(part_md, &md->part, part) {
  			mmc_queue_resume(&part_md->queue);
  		}
+		pm_runtime_put(&card->dev);
  	}
  	return 0;
  }
Hi Ulf
Currently, I am implementing a patch that facilitates each device to manage is runtime pm on its own. I am using the parent-child relationship that is already established in the mmc stack for this implementation. In this case, mmc_card is a child of mmc_host which is in turn is the child of platform-device. The following contexts exist which would have to invoke get_sync and put_sync on the mmc_card device:
1. mmcqd
2. bkops
3. mmc_rescan

The get_sync on card device would resume all the 3 devices starting from the platform-device and the put-sync would suspend all the 3 devices starting from the card-device. pm_auto_suspend/pm_schedule_suspend may be used to trigger the suspend from the above contexts.
I believe this would simplify the runtime pm functionality.

I can put up the patch for review in a couple of days.

Please let me know your opinion about this approach.

--
Thanks
Asutosh

--
Sent by a consultant of the Qualcomm Innovation Center, Inc.
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum.

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