On Monday 13 May 2013 20.46.40 Ming Lei wrote: > On Mon, May 13, 2013 at 12:58 PM, Frederik Schmid > > <frederik.schmid@xxxxxxxxx> wrote: > > Ming, > > > > The ehci controller is bogged down because the frames from the camera and > > other stuff are being relayed over ethernet. > > If you mean usb camera and usb ethernet need to be used at the same > time, it might > be a problem, suppose your camera runs at the high bandwidth(3*1024/uframe), > so the streaming speed is 24MByte/sec, and USB ethernet interface(100M) > can't send the streaming data out as quickly as the camera. > That's basically it. What complicates things further is that the camera doesn't use ISO-endpoints, it uses bulk-endpoints. > But if you plan to connect your usb camera onto musb, it is still not > a good idea > since musb can't give a good user experience to do periodic transfer, since > CPU may not handle IRQ very quickly(it is often to see interrupt disabled > for more than 1 millisecond on OMAP4 sometime), so the period of > Isochronous transfer can't be set very much(1ms/period and less may not run > well), otherwise streaming packets are dropped frequently by musb hardware > even though you enable double buffer mode. > > So why don't you choose to connect your camera onto EHCI, and ethernet > interface onto musb? That might be a solution, however, the CPU-modules from Variscite are already hardwired for the current configuration. Best regards, Frederik -- 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
