bpa wrote: > I have a Cubieboard (Allwinner A10) based dev board. There are a few > kernels ported to it. > Although data sheet indicate EHCI support I suspect it is like all the > other ARM SOC where the implementation may not be sufficient. > However teh A10 has USB and USB OTG interfaces and they are implemented > separately in silicon so perhaps the USB OTG might have a good ehci > implementation. > I think the on chip spdif only works to 48kHz > > Rather than just lobbing loads of suggestions for alternative chips > without qualification, is there any test or procedure that can be > performed > > 1. To determine if ehci is a good implementation without having a 96Khz > DAC. > 2. To determine if a kernel has the right scheduling/RT options.
I actually believe its the other way round. Real hardware EHCI by its nature has a calander in hardware of more than one packets worth of what to send and when (256 ms worth by memory in the touch config). All of the OTG IP blocks things which do OTG as well as host mode seems to reduce the gate count by offloading things to software and have alternative drivers as they don't use the ehci hardware driver. I suspect they are fine for general USB use, but we need isochronous transfers which means we not only want to send the data, but also send it in the right instance in time - i.e. the right frame and microframe. Anything which relies on software to compute this each packet via interrupts is going to carry high interrupt load (and as Pi shows if done badly will be faitally flawed). The EHCI implementations which are host only ports on arm SoCs seem to work ok - Touch, Cubox work for me; they all suffer with a restricted TT, so need an external hub, but they do seem to be ok for async dacs from what I can tell. Kernel scheduling is more a matter for getting low latency, we can mitagate this up with higher alsa buffers if needed. But it would be nice to get to low latency and ideally to the have the config_preempt_rt patches so we can make it as good as touch. ------------------------------------------------------------------------ Triode's Profile: http://forums.slimdevices.com/member.php?userid=17 View this thread: http://forums.slimdevices.com/showthread.php?t=97881 _______________________________________________ discuss mailing list discuss@lists.slimdevices.com http://lists.slimdevices.com/mailman/listinfo/discuss
