On 06/24/2013 05:18 PM, Felipe Balbi wrote: >> It is a little. The first USB packet has 512 vs 502 bytes on the >> wire. > > you wouldn't notice the difference. The DMA engine is the one > which would read the sgtable to figure where the data is scattered, > at the end of the day, SW only knows of a single 1044bytes URB and > controller is required to generate proper USB packets out of that. The DMA engines (intern or extern) do not merge transfers. Some of them are clever enough to transfer a single 1024 as two 512 requests. But two 256 bytes requests are not merged into one 512 request. I believe the device side of dwc3 is able to do so if marked properly but musb host side won't be able to do so. Sebastian -- 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
