hi, On Mon, 2015-10-19 at 14:25 +0300, Mathias Nyman wrote: > >> > >> 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. > It doesn't say that the packets should be transfered within the same microframe (bus interval), as I understand it means service interval; The direct prove resides in figure 8-56/8-57. Term: 1. BI, bus interval, a 125 us period that establishes the internal boundary of service interval, aka uframe; 2. SSI, Support Smart Isochronous; 3. DBI, Data in this Bus Interval is done; 4. NBI, Numbers of Bus Interval; As the figure shows, the service interval = 8 BI, that host distribute 2 packets @1st uframe, keep U1/U2 state for the next 3uframe, then transmit 4 packets @4th uframe, and the remaining 3 packet in the last frame. Please notice that this just is an example illustrated by spec, but we can derive the conclusion that the distribution of packet in a service interval is completely decided by host, and can split isoc transfers across multiple uframes. PS: as you can see, MTK implementation of schedule algorithms is an implementation of Smart Isochronous of which the smart side resides in software. > -Mathias > > > > > -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
