On Mon, Nov 4, 2013 at 11:51 AM, Alan Stern <stern@xxxxxxxxxxxxxxxxxxx> wrote: > On Mon, 4 Nov 2013, Cliff Brake wrote: >> We have the same system running on a older PXA270 version of the >> product (vs the current TI DM3730). It has an older OHCI 12Mbit USB >> host controller (vs the current TI EHCI controller). We have _not_ >> experienced these types of latencies with the older PXA270 product. >> This may be another indication the problem lies in the TI EHCI >> controller driver, but its odd we have not seen any issues with other >> peripherals. > > More likely it's an indication that you aren't transferring such large > amounts of data with the older host. The trace shows very clearly that > the lion's share of the overhead was not in the EHCI controller driver; > it was in the HID processing. I did comparison function traces with the PXA270 and DM3730 system, and the big difference is the older (gen1) system is only using 64 byte packets, where the newer one is using ~700 byte packets. See: http://bec-systems.com/usb-trace-gen1_filtered.txt http://bec-systems.com/usb-trace-gen2_filtered.txt I assume interrupts are disabled during both ohci_irq() and ehci_irq(). Short term we'll try to force 64-byte packets on the EHCI system. Long term it would be nice if this work did not happen in a irq handler, although this is clearly an abuse of the HID protocol. Thanks, Cliff -- 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
