> On 2018Jul26, at 01:56, Alan Stern <stern@xxxxxxxxxxxxxxxxxxx> wrote:
>
> On Wed, 25 Jul 2018, Kai-Heng Feng wrote:
>
>> 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 <kai.heng.feng@xxxxxxxxxxxxx>
>> ---
>> 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
--
To unsubscribe from this list: send the line "unsubscribe linux-usb" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
