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.
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.
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