Alan, On Fri, Jan 22, 2016 at 11:48 AM, Alan Stern <stern@xxxxxxxxxxxxxxxxxxx> wrote: > On Thu, 21 Jan 2016, Doug Anderson wrote: > >> This doesn't sound familiar to me, but as far as I know all the >> official Raspberry Pi kernels use a pretty different dwc2 driver. See >> the (non-mainline) code in drivers/usb/host/dwc_otg/ in the Raspberry >> Pi tree at <https://github.com/raspberrypi/linux.git>. > > Ah, thanks for that pointer. I also found the page at raspberrypi.org > which describes how to build and install a custom kernel. > >> The Raspberry Pi driver and the mainline driver are pretty different >> (though they have the same heritage). As far as I remember the >> Raspberry Pi driver has feature to enable FIQ for helping deal with >> some of the dwc2 issues. That gives it a chunk of code that's totally >> rewritten... > > Indeed, dwc_otg is quite different from dwc2. I found what appears to > be a bug in the dwc_otg's _hub_info() routine. (This is the subroutine > that gets the upstream hub address and port number for devices behind a > TT.) It does: > > *port_addr = urb->dev->tt->multi ? urb->dev->ttport : 1; Hrm. Yeah, in the mainline driver it looks like we just have: void dwc2_host_hub_info(struct dwc2_hsotg *hsotg, void *context, int *hub_addr, int *hub_port) { struct urb *urb = context; if (urb->dev->tt) *hub_addr = urb->dev->tt->hub->devnum; else *hub_addr = 0; *hub_port = urb->dev->ttport; } > However, the USB spec says that the SPLIT packet's third byte is > supposed to contain the port for both single-TT and multi-TT hubs. > And sure enough, the upstream hub for this non-working device is > single-TT. Presumably that explains why the third byte in the SPLIT > packet was 0x01 rather than 0x04. > > The corresponding line in the dwc2_host_hub_info() routine simply does: > > *hub_port = urb->dev->ttport; > > Unfortunately, even after I changed the dwc_otg routine the device > still didn't work. My bus analyzer isn't on hand today, so I'll have > to work on it more next week. > >> It would be really interesting to see if the patch series I just >> posted helps you (it fixes lots of problems in the mainline driver >> with splits), though it might still not be enough on the Raspberry Pi >> since the CPU clock there is much slower than on my 1.8GHz A12-based >> system and thus maybe FIQ is a must have there... > > Can you tell me how to configure a mainline kernel to work on the > Raspberry Pi? There is no arch/arm/configs/bcmrpi_defconfig. Not offhand. Again, perhaps someone else on this thread will have more. I did do a quick Google search and came up with: http://elinux.org/RPi_Upstream_Kernel_Compilation ...but the Raspberry Pi I have at home is running some home automation stuff so I don't want to give that a try. :-P -Doug -- 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
