On 2013/3/28 22:46, Alan Stern wrote:
On Thu, 28 Mar 2013, Lan Tianyu wrote:
How long do you think the power should remain turned off? This code
will leave it off for only a few milliseconds at most. That may not
even be long enough for the voltage to drop all the way to 0.
The delay probably should be at least 100 ms. Maybe more, I don't
know.
I think this depends on the device. I don't find the answer on spec.
I find the cool down delay of over-current for port is 100ms
and one for hub is 500ms. Could we reference these delay?
500ms would be safe.
Okay, then use 500 ms.
Alan Stern
Ok.
About the path "usb: Add usb port system pm support", do you think it's
ok?
On 2013/3/28 2:47, Alan Stern wrote:
What happens if there's no device plugged in to the port, but the hub
is enabled for remote wakeup? How will the hub be able to detect a
plug-in event if the port isn't powered?
Alan Stern
Hi Alan:
Great thanks for your review.
The hub will not detect the new devices. From my opinion, this
depends on the user space since the port only will be powered off when
pm qos NO_POWER_OFF flag is unset(it is default to be set). If unset
the flag, losing plug-in event should have been took into account.
--
Best Regards
Tianyu Lan
linux kernel enabling team
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