> -----Original Message----- > From: Rafael J. Wysocki [mailto:rjw@xxxxxxx] > Sent: Friday, March 01, 2013 8:51 AM > To: Liu, Chuansheng > Cc: Alan Stern; Li, Fei; gregkh@xxxxxxxxxxxxxxxxxxx; Lan, Tianyu; > sarah.a.sharp@xxxxxxxxxxxxxxx; linux-usb@xxxxxxxxxxxxxxx; > linux-kernel@xxxxxxxxxxxxxxx > Subject: Re: [PATCH 4/5 V2] usb: call pm_runtime_put_sync in > pm_runtime_get_sync failed case > > On Friday, March 01, 2013 12:38:07 AM Liu, Chuansheng wrote: > > > > > -----Original Message----- > > > From: Alan Stern [mailto:stern@xxxxxxxxxxxxxxxxxxx] > > > Sent: Thursday, February 28, 2013 11:17 PM > > > To: Li, Fei > > > Cc: gregkh@xxxxxxxxxxxxxxxxxxx; Lan, Tianyu; > sarah.a.sharp@xxxxxxxxxxxxxxx; > > > rjw@xxxxxxx; linux-usb@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; Liu, > > > Chuansheng > > > Subject: Re: [PATCH 4/5 V2] usb: call pm_runtime_put_sync in > > > pm_runtime_get_sync failed case > > > > > > On Thu, 28 Feb 2013, Li Fei wrote: > > > > > > > > > > > Even in failed case of pm_runtime_get_sync, the usage_count > > > > is incremented. In order to keep the usage_count with correct > > > > value and runtime power management to behave correctly, call > > > > pm_runtime_put(_sync) in such case. > > > > > > > > Signed-off-by Liu Chuansheng <chuansheng.liu@xxxxxxxxx> > > > > Signed-off-by: Li Fei <fei.li@xxxxxxxxx> > > > > --- > > > > drivers/usb/core/hub.c | 3 ++- > > > > 1 files changed, 2 insertions(+), 1 deletions(-) > > > > > > > > diff --git a/drivers/usb/core/hub.c b/drivers/usb/core/hub.c > > > > index 5480352..f72dede 100644 > > > > --- a/drivers/usb/core/hub.c > > > > +++ b/drivers/usb/core/hub.c > > > > @@ -3148,12 +3148,13 @@ int usb_port_resume(struct usb_device > *udev, > > > pm_message_t msg) > > > > > > > > if (port_dev->did_runtime_put) { > > > > status = pm_runtime_get_sync(&port_dev->dev); > > > > - port_dev->did_runtime_put = false; > > > > if (status < 0) { > > > > dev_dbg(&udev->dev, "can't resume usb port, > status %d\n", > > > > status); > > > > + pm_runtime_put_sync(&port_dev->dev); > > > > return status; > > > > } > > > > + port_dev->did_runtime_put = false; > > > > } > > > > > > I don't see much point in this. After a failed resume, the port's > > > runtime PM status is undefined. Whether or not you do a > > > pm_runtime_put_sync won't make any difference. > > In case of failed resume, calling pm_runtime_put_sync() is just for decrease > the dev->power.usage_count, > > because pm_runtime_get_sync() always increase the > dev->power.usage_count even failed. > > > > If not pairing runtime_get/put, after that case, the device can not enter > runtime suspend any more due to dev->power.usage_count > 0 always. > > Is it making sense? > > Well, not really. > > Before returning an error code, rpm_callback() assigns that code to > dev->power.runtime_error and that will effectively disable runtime PM for dev > going forward anyway. Thanks your pointing out. dev->power.runtime_error!=0 will really block the runtime PM resume/suspend to continue. But in case of rpm_resume return error when dev->power.disable_depth > 0, the dev->power.runtime_error is not set yet. Is it the case? Thanks your comments again. And another case is when user called pm_runtime_set_status to clear the runtime_error after dev->power.runtime_error is set during pm_runtime_get_sync(), the runtime_resume/suspend() can be tried again? But the dev->power.usage_count is still wrong? Thanks your correction again:) > > Thanks, > Rafael > > > -- > I speak only for myself. > Rafael J. Wysocki, Intel Open Source Technology Center. ��.n��������+%������w��{.n�����{���)�� jg��� �����ݢj����G���� ���j:+v���w�m������w�������h�����٥
