On Tuesday 19 February 2008, Pandita, Vikram wrote: > USB EHCI/OHCI experts > > On omap-git v2.6.25-rc2, TI OMAP34xx EHCI controller, we are seeing a > strange behavior on a bulk OUT 512 byte transfer. > > We can see through the CATC that the 512 byte goes out successfully > but there are many Turnaround/Timeout Errors and retries before the > packet goes out successfully. > The retries could range from 0 to 10 or more. > > The error packets have 'CRC16 complemented' as per Section 8.6.4 > page 234-235 that says for probably a data under-run condition: > "An error for high-speed must be forced by taking the currently > calculated CRC and complementing it before transmitting it." > > We have confirmed that our Memory (SDRAM) access have a much higher > bandwidth available "not" to cause data under-run condition. > > Where in EHCI stack should I debug for this issue? Doesn't sound like an EHCI driver issue. I'd want to track what's going on deeper inside the silicon than ARM instruction set handling ... ;) > Is there a way to slow-down the OUT transfers on EHCI if that > helps in debugging? You could issue URBs with single packets. If you're not using the "usbtest" framework, you should start ... that command line tool lets you send a variety of packet sequences. You'll want some high speed source/sink device, like another board running the "Gadget Zero" firmware. - Dave [1] http://www.linux-usb.org/usbtest/ - To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
