With respect to latest xHCI spec : Revision 1.0 with errata to 8/14/12 Page 114: Note: Consider the case where there are multiple TDs posted for pipe for a single data transfer and a Short Packet or other condition on one TD means that the data transfer is terminated, and that the subsequent TDs associated with the data transfer are now invalid. The xHC may have read ahead on the Transfer Ring and cached the subsequent TDs. To ensure that xHC frees any cached information associated with a pipe in a timely manner (so that it can reuse the cache space for other pipes), software shall issue a Set TR Dequeue Pointer Command for the pipe when the data transfer is terminated, vs. waiting for the next data transfer to be ready before issuing the command. Note: If software issues a Set TR Dequeue Pointer Command that points to a TRB that had previously been partially completed TD, the xHC shall treat that TRB as the first TRB of the TD. i.e. any prior state associated with a partially completed TRB is lost. Looking at this description, I interpret that when the ShortPacket is received, xHC should stop executing the transfer and should wait for the driver for next command or doorbell. Page 130: Note: If the xHC receives a short packetShort Packet from a device, then it shall retire the current TD. If another TD is defined on the Transfer Ring, the xHC shall advance to it and begin IN transactions. Looking at this description, I interpret that when the ShortPacket is received, xHC should discard the current TD and start executing the next TD if available. Page 172: If a Short Packet is detected during the execution of a multi-TRB TD, the xHC shall advance to the first TRB of the next TD or the Enqueue Pointer (i.e.Cycle bit transition), whichever is encountered first. Looking at this description, I interpret that when the ShortPacket is received, xHC should discard the current TD and start executing the next TD if available. These descriptions are contradictory. Which is the correct xHCI behavior when ShortPacket is received? -Ankit -- 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
