On 28.10.21 19:00, Pali Rohár wrote:
On Thursday 28 October 2021 16:20:11 Stefan Roese wrote:
On 28.10.21 13:04, Pali Rohár wrote:
On Thursday 28 October 2021 08:16:24 Stefan Roese wrote:
On 27.10.21 23:03, Pali Rohár wrote:
On Wednesday 27 October 2021 17:27:41 Stefan Roese wrote:
Still I see no speed change. But this is a different story...
Could you try to upload some file in u-boot via xmodem at different speeds? E.g. via loadx command:
loadx <addr> 921600
and
loadx <addr> 115200
loadx & loady are producing nearly the same numbers on my Armada XP target for download (slow of cause). This is really strange.
Ok. So it means that the issue should not be in kwboot, if also U-Boot xmodem implementation is affected.
Agreed.
I also tested with "normal" console actions (logging) with higher baudrates. Here these numbers:
time md 2000000 10000:
115200 baud: time: 1 minutes, 32.694 seconds
921600 baud: time: 11.587 seconds
92.7s vs 11.6s -> factor ~8. Which is exactly the baudrate difference. So at least here I see a speed difference, which means that the USB UART converter must be working in general. I really have no idea right now to explain, why this does not any speed differences while downloading.
So this means that USB-UART converter must work also on higher speeds.
My idea is that there is some significant overhead on USB-UART when accessing either RX or TX queue. xmodem protocol is: send 132 bytes, wait for 1 byte reply, send another 132 bytes, wait again for 1 byte reply, ... So if USB-UART has internal overhead which cause that every byte is postponed by some delay then it would mean that xmodem is most time just waiting, meaning overhead is applied for every one 132-byte long packet. Test with md cause continuous stream of data, therefore such overhead is applied only at beginning of the md transfer.
Similar issues with can observed also on high speed networks were is very big latency when using protocols where each small packet has to be acknowledged. TCP is using windowing to prevent such kind of issues.
And kermit protocol too via its streaming mode. So kermit transfer could prove if this is really that issue.
Anyway, I have looked at your strace output again and I saw that there is a long gap after tcdrain() and end of the read(). So if kernel implements tcdrain() for your USB-UART hw it means that it take too much time to receive reply byte from USB-UART hw to the kernel. So it could be another indication of that overhead.
Thanks for the input here.
And compare if xmodem transfer is in U-Boot faster or not. Ideally also try via kermit protocol at different speeds as kernel supports streaming.
I'm currently struggling to get gkermit working on my Ubuntu machine - so no numbers here yet, sorry.
In U-Boot console call:
loadb _addr_And then quit terminal emulator used for U-Boot /dev/ttyUSBX device. Then run gkermit with following arguments:
gkermit -i -X -s _file_to_send_ < /dev/ttyUSBX > /dev/ttyUSBX(redirecting both stdin and stdout is required)
After successful transfer gkermit exit. BEWARE that gkermit does not print any progress information and neither any error. So do not kill gkermit via CTRL+C prematurely. You can use "time gkermit ..." for measuring total transfer time.
If you are going to use different speed than 115200 in u-boot run:
loadb _addr_ _speed_And then on host start gkermit with more commands around:
stty -F /dev/ttyUSBX _speed_ printf '\015' > /dev/ttyUSBX gkermit -i -X -s _file_to_send < /dev/ttyUSBX > /dev/ttyUSBX sleep 0.5 stty -F /dev/ttyUSBX 115200 printf '\033' > /dev/ttyUSBXDue to absence of progress bar and error information I'm using ckermit application for kermit file transfers. But for testing purposes is gkermit application here also fine.
Ah, perfect. Here my number now using these steps and gkermit, with a file size of 549373 bytes:
115200 baud: ~72 sec 921600 baud: ~11 sec
So I think it is clear now. Either USB-UART HW or kernel driver for it has some big overhead for any protocol which needs acknowledgement of received data. So xmodem protocol is not suitable for it.
It would require to debug kernel driver and ideally monitor traffic on oscilloscope to see where exactly is the issue.
And because bootrom supports only xmodem protocol we cannot do more in kwboot.
Agreed. Let's close this issue here. Important is, that kwboot still works on all supported SoC's - even if the speedup improvements may not be available for all boards.
Thanks for all your work here, Stefan