On 01/13/2014 05:11 PM, Felipe Balbi wrote:
160MBit/sec isn't terrible, but I hoped for better. A USB analyzer
shows 7 transactions happening quickly (with about 14us separating
them), but every 8th transaction, the EG20T will NAK between 20-80
times[1], losing 50-100us[2].
as Alan stated, this is a problem on the device side. The device is
replying with NAK because, I believe, it has ran out of free TDs.
What am I missing?
you should probably profile your pch_udc_pcd_queue() to figure out if
there's anything wasting a lot of time there.
Unlike Alan, I would use trace_printk() rather than pr_debug() since
trace_printk() is of much lower overhead. Google around and you'll see
how to use trace_printk() and how to use the kernel function profiler.
Alan and Felipe,
Thanks for the insight. I'll do some tracing and try to get it narrowed
down.
Alan.
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