[2/5] memstick: Prevent memstick host from getting runtime suspended during card detection

On 2018Jul26, at 01:56, Alan Stern [off-list ref] wrote:

On Wed, 25 Jul 2018, Kai-Heng Feng wrote:

quoted

We can use MEMSTICK_POWER_{ON,OFF} along with pm_runtime_{get,put}
helpers to let memstick host support runtime pm.

There's a small window between memstick_detect_change() and its queued
work, memstick_check(). In this window the rpm count may go down to zero
before the memstick host powers on, so the host can be inadvertently
suspended.

Increment rpm count before calling memstick_check(), and decrement rpm
count afterward, as now we are sure the memstick host should be
suspended or not.

Signed-off-by: Kai-Heng Feng <redacted>
---
drivers/memstick/core/memstick.c | 4 ++++
1 file changed, 4 insertions(+)

diff --git a/drivers/memstick/core/memstick.c b/drivers/memstick/core/memstick.c
index 76382c858c35..944fe0c93fa7 100644
--- a/drivers/memstick/core/memstick.c
+++ b/drivers/memstick/core/memstick.c

@@ -18,6 +18,7 @@

#include <linux/delay.h>
#include <linux/slab.h>
#include <linux/module.h>
+#include <linux/pm_runtime.h>

#define DRIVER_NAME "memstick"

@@ -209,6 +210,7 @@ static int memstick_dummy_check(struct memstick_dev *card)
 */

void memstick_detect_change(struct memstick_host *host)
{
+	pm_runtime_get_noresume(host->dev.parent);
	queue_work(workqueue, &host->media_checker);
}
EXPORT_SYMBOL(memstick_detect_change);

@@ -479,6 +481,8 @@ static void memstick_check(struct work_struct *work)

		host->set_param(host, MEMSTICK_POWER, MEMSTICK_POWER_OFF);

	mutex_unlock(&host->lock);
+
+	pm_runtime_put_noidle(host->dev.parent);
	dev_dbg(&host->dev, "memstick_check finished\n");
}

This should be pm_runtime_put(), not _put_noidle().  The reason is
because if this call causes the PM runtime usage count to drop to 0,
you do want the device to go into runtime suspend.

Will update in next version, thanks!

Kai-Heng

Alan Stern

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