On 2023/12/21 00:02, Frank Li wrote: >>> Some UDC driver use gadget_check_config() and match_ep() to allocate EP >>> internal fifo memory resource, if only pass download full speed EP. >> Could you share the detail of problem ? do you mean find another different endpoint compared > The problem is little bit complex. I try to use simple words. > > The background: > > Generally, UDC have some EP<0..15> and have some internal memory as FIFO. > for example 16K. You can simple assign EP<n> to 1K memory, which can hold > whole package. > > But for UVC, some controller required internal FIFO hold whole frame data > > (mult+1) * (MaxBurst +1) * wPackageSize. > > For most case, not every gadget use all 16 EPs. So you can assgin more > memory into one EP, so it will reduce bus 'ping' package number and reduce > NACK to improve transfer speed. > > The problem: > pass fs_stream to udc driver, udc driver's check_config function will see > mult and maxburst is 0. so only reserve 1K for ISO EP, but when try to > enable EP, mult is 2, so there are not enough internal memory for it > because more memory already assign to other EPs. > > Ideally, when gadget frame work can call check_config again when know > usb speed, but it is not easy to fix it. > > Simple method use ss_stream_ep here and other function drviers. Super > speed's package size is bigger than high/full speed. If resource can > support super speed, it can support high/full speed. I don't find any difference of uvc_ss_streaming_ep, uvc_hs_streaming_ep, uvc_fs_streaming_ep descriptors. how difference happen in UDC ? > > > /** > * gadget_is_superspeed() - return true if the hardware handles superspeed > * @g: controller that might support superspeed > */ > > @max_speed: Highest speed the driver handles > > And according to gadget_is_superspeed() define, it indicate if udc > controller support supersped, not link speed. > > Orignial code is correct. If UDC support superspeed, then use ss_stream_ep. > > becasue superspeed is worse case compared as high and full speed. > > So I think original is correct. > > Frank. > >
