hi Alan: 2013/12/1 Alan Stern <stern@xxxxxxxxxxxxxxxxxxx>: > On Fri, 29 Nov 2013, vichy wrote: > >> hi all: >> My connection like below >> ehci --> high speed hub -> full speed device >> >> I have some questions about period scheduling. >> 1. when creating qh for full speed device, why we set EHCI_TUNE_RL_TT. > > Are you asking why EHCI_TUNE_RL_TT is equal to 0? I don't know -- it > looks like a mistake. Do you find that changing it to 3 makes any > difference? Yes, when I change EHCI_TUNE_RL_TT as not 0. The transaction can keep going. > >> isn't it possible the full speed device return NAK during transaction? > > Of course it is possible. If so, why we use EHCI_TUNE_RL_TT default as 0? > >> that mean once it react with NAK, the host will stop below transaction. > > The host stops the transaction temporarily. It will restart the > transaction later. See section 4.9.1 in the EHCI spec. I find what you mentioned. > >> How could we make sure device never react with NAK? > > There is no way to do that. > >> 2. I attach my mon log for your reference. >> there is one thing I am curious >> why below message 'E' mean in bulk/interrupt? >> I have checked Document/usb/usbmon.txt but get nothing. > > E means the preceding submission failed. > >> d8c32600 190047566 E Bi:1:006:2 -19 0 >> d8c32980 190062351 C Bi:1:006:2 -107 0 >> d8c32980 190062363 S Bi:1:006:2 -115 1025 < >> d8c32980 190072803 E Bi:1:006:2 -19 0 > > For example, this E means the submission on the line above was > unsuccessful. The error code -19 is -ENODEV, which means the device > has been disconnected. > > This is described in Documentation/usb/usbmon.txt: > > - Event Type. This type refers to the format of the event, not URB type. > Available types are: S - submission, C - callback, E - submission error. Thanks for your help -- 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
