Messages in this thread | | | Date | Mon, 19 Oct 2015 14:25:49 +0300 | From | Mathias Nyman <> | Subject | Re: [PATCH v9 4/5] xhci: mediatek: support MTK xHCI host controller |
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>> >> So basically we are trying to use as many microframes as possible with as few packets >> per microframe as possible. >> >> Did I understand this correctly? > Yes, you are right. > >> How will devices react if they expect to get 16 packets every 16th microframe, >> but they get one packet every microframe instead? > I think that the synchronous endpoint must specify its period by > bInterval, but can't specify how data should be transfered during the > period by the host, and it just only receives data passively. So the > device can receive data correctly in the case(bInterval is 5). > > quote from usb3_r1.0 section4.4.8 Isochronous Transfers: > "The host can request data from the device or send data to the device at > any time during the service interval for a particular endpoint on that > device" >
As I understand the 4.4.8 section it just means the device can't assume a fixed time interval between transfers, meaning that the host can use the last microframe in one esit and the first microframe in the next esit, but still only use 1 microframe per esit.
Section 8.12.6.1 describes how a 11 packet isoc transfer is allowed to be split to 1 burst of 11 packets, 2 burst (8 + 3), 3 burst (4+4+3) 6 bursts (2+2+2+2+2+1) or 11 bursts of 1. These are however all within the same microframe. Splitting the transfer into several microframes in a esit kind of makes the whole interval concept pointless.
-Mathias
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