On Tue, Jan 14, 2014 at 9:26 PM, Alan Ott <alan@xxxxxxxxxxx> wrote: > On 01/14/2014 09:13 AM, Felipe Balbi wrote: >> >> On Mon, Jan 13, 2014 at 11:25:16PM -0500, Alan Ott wrote: >>> >>> On 01/13/2014 09:01 PM, Alan Stern wrote: >>>> >>>> On Mon, 13 Jan 2014, Felipe Balbi wrote: >>>> >>>>> On Mon, Jan 13, 2014 at 03:20:31PM -0500, Alan Ott wrote: >>>>>> >>>>>> I have an EG20T-based board and have some issues with performance on >>>>>> the USB device interface. >> >> >> I'll shoot in the dark here and assume current pch_udc only starts >> request N after N-1 has been givenback, and that's probably what's >> causing the extra delay. > > > Yes, that's what it looks like from my analysis. The DMAs work on the > transfer level though (one DMA per USB transfer), so making larger transfers > increases the performance significantly. > > >> Just as a debugging effort, can you move the call to giveback to a >> workqueue or something like that just so it gets scheduled into the >> future ? This wouldn't be an acceptable patch, but just to see if my >> statement is valid. Generally this delay caused due to processing rather than the pdc driver. I blv in this case checking of data and memset could be the cause for delay. Had tried workqueue for a different PDC driver but didnt change things because mostly completion is necessary before taking the next action. > > > Do you mean move the starting of the next transfer (after a transfer > completes) to a workqueue to delay it further? (for testing of course). > > > Alan. > > -- > 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 -- 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
