On Thu, 2019-08-22 at 13:30 -0400, Alan Stern wrote: > On Thu, 22 Aug 2019, Benjamin Herrenschmidt wrote: > > > On Thu, 2019-08-22 at 14:58 +1000, Benjamin Herrenschmidt wrote: > > > > > > Ah lovely ... the 338x fails in EP autoconf with f_tcm, digging... > > > > > > While digging I found this gem: > > > > > > /* USB3380: use same address for usb and hardware endpoints */ > > > snprintf(name, sizeof(name), "ep%d%s", usb_endpoint_num(desc), > > > usb_endpoint_dir_in(desc) ? "in" : "out"); > > > ep = gadget_find_ep_by_name(_gadget, name); > > > if (ep && usb_gadget_ep_match_desc(_gadget, ep, desc, ep_comp)) > > > return ep; > > > > > > Any idea what's that supposed to achieve ? > > It looks like in one mode, the endpoint number has to be the value > predetermined by the hardware. In the other mode, any hardware > endpoint can be assigned any endpoint number. Sure but as I wrote, this is ep_match, which when called, always has usb_endpoint_num() set to 0... this function is supposed to chose the EP number afaik. So I don't think the above ever works, it just returns NULL. Or do we ever call this again with already predetermined EP nums, for example when doing multifunction ? > > > When ep_match is called, usb_endpoint_num() hasn't been set yet so > > > it's always 0 and always fails... or am I missing something ? > > > > Two problems: > > > > - net2280.c doesn't set a max EP size, so autoconfig fails since > > f_tcm specifies one. What about this ? > > > > --- a/drivers/usb/gadget/udc/core.c > > +++ b/drivers/usb/gadget/udc/core.c > > @@ -940,12 +940,14 @@ int usb_gadget_ep_match_desc(struct usb_gadget *gadget, > > if (usb_endpoint_dir_out(desc) && !ep->caps.dir_out) > > return 0; > > > > - if (max > ep->maxpacket_limit) > > + if (ep->maxpacket_limit && max > ep->maxpacket_limit) > > return 0; > > > > (ie assume that ep->maxpacket_limit 0 means the UDC supports any > > legal size) > > That looks reasonable. I'll send a patch. > > - No UDC driver other than dummy sets max_streams, and f_tcm requires 4, > > so f_tcm will fail with *any* superspeed UDC driver as far as I can tell. > > > > Was it ever tested with USB 3 ? > > Note that USB 2 does not support streams at all. Yes, f_tcm only requires them for superspeed, but it does *require* them in that case. > > I'm not sure what the right fix here yet is as I yet have to learn about > > what those USB3 streams are :-) For now I've commented things out. > > They are for multiplexing multiple data streams over a single USB > endpoint. As far as I know, the only use case for such a thing is USB > Mass Storage. So f_tcm could operate in a degraded mode in the absence of streams easily, the problem is the mechanics of EP matching in epautoconf. It will just fail. I wonder since f_tcm is also the only user, whether we could change the matching logic to either: - Don't try to match, return streams is available. This could be problematic if the UDC supports streams on some EPs and not others however. - Do two passes: one pass trying to match the streams, and one patch without matching them if the first one fails. Then f_tcm could check whether it got EPs with streams and enable stream usage accordingly. Opinions ? Other option ? Cheers, Ben.
