On 2012年11月11日 23:46, Alan Stern wrote: > On Sun, 11 Nov 2012, Lan Tianyu wrote: > >> Hi Alan: >> Great thanks for your review and good suggestions. >> I think the main problem is that when the port device resumed(you said >> turn on/off power in the port's runtime callback ) and device powered on >> again, If we did't resume the device and suspend again, the device would >> be at uninitalized state(I guess it should be unattached state actually) >> until resume it, right? > > No. The device will be in the POWERED state at first, but it will > quickly change into the SUSPENDED state. > >> This will consume more power than suspend it >> agian. > > No it won't, because the device will suspend itself after 3 ms. But the premise is "they see a constant Idle state on their upstream facing bus lines for more than 3.0 ms", that means the port's suspend feature should be set to prevent all the bus activity(e.g sof), right? Now I have another concern that the device will maintain address 0 after repower and not reset-resume. What happen if another device was plugged in? > >> So from my opinion, the device should be resumed when port >> resumes. After autosuspend delay timeout, the device will suspend again. >> If I remember correctly, pcie port and sata port do the same thing that >> port will resume its children when it resumes. > > That doesn't mean USB has to do the same thing. > > Alan Stern > -- Best regards Tianyu Lan -- 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
