On Sun, 2016-06-12 at 18:13 +0100, Bryan O'Donoghue wrote:

On Tue, 2016-06-07 at 13:04 +0300, Andy Shevchenko wrote:

quoted

quoted

I'll find some time to look at both a short stream and a long

stream,

quoted

based on the branch you've indicated and maybe against the latest
stable kernel.

Please, do. I'm planning to resend new version soon (this week or
lately beginning of the next one).

So.

Generally DMA appears to make little-to-no difference here.

Yes, because your test shows the speed of the serial data line.

What we are trying to measure here?

If you would like to measure CPU load it will require threaded
application and some load task to see the difference. Another metric
which may help is interrupt counters. I'm wondering if perf can help
here as well.

One thing I have noticed is that the following never completes and
can't be reset back to mode=0 or mode=3 to restore functionality -
definitely worth looking at if you are spinning another patch.

### never completes ####
root@galileo:~# echo 1 > /sys/class/tty/ttyS0/dma_mode
root@galileo:~# stty -F /dev/ttyS0 921600
root@galileo:~# time cat tester.txt > /dev/ttyS0
### never completes ####

Thanks for that test, I will try to reproduce on my side.

-- 
Andy Shevchenko [off-list ref]
Intel Finland Oy