Hi, On Tue, Apr 18, 2017 at 1:07 AM, Stefan Wahren <stefan.wahren@xxxxxxxx> wrote: >> 1. With dwc2 you often end up in the situation where you need to >> service an interrupt every 125 uS. If servicing that interrupt takes >> anywhere near 125 uS in the common case then you'll be in trouble. > > I will try to measure this with a logic analyzer. Why a logic analyzer? I'd think that "ftrace" would be your friend here. If you configure it just right you ought to be able to figure out exactly what your kernel is doing. ...or, if you don't want to learn ftrace (it's cool and worth it, but there's some time) you can just use "trace_printk" to get a fairly low-over head printout to a memory buffer. You can put that printout in various places in the code and figure out what's taking so long. In fact, that's exactly how the patch at <https://chromium-review.googlesource.com/c/321980/4/drivers/usb/core/hcd.c> works. -Doug -- 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
