AnsweredAssumed Answered

iMX6UL Ethernet performance issue with LCD

Question asked by Durmuş Kurtuluş on Dec 7, 2016
Latest reply on Aug 15, 2017 by Durmuş Kurtuluş



I'm testing the ethernet performance of my custom iMX6UL board (based on EVK board):

Linux BSP version: 3.14.52_1.1.0

Ethernet port: FEC1

PHY & speed: KSZ8081RNB & 100 Mbps full-duplex

Test method: Transferring a large file (1.5 GB) via sftp using FileZilla

LCD: 7" (800x480 px), refresh rate=60Hz (lcd_frequency corresponds to 33.3MHz)


With lcdif disabled:

There is no problem at all. The file transfer progresses with a nice 3.5 MB/s speed. I check the output of "ifconfig" for errors and there are none.


With lcdif enabled:

When just the console output is on the screen there seems to be no problem with file transfer, but I see some occasional RX errors in "ifconfig" output.

When I run a gui application, file transfer speed drops significantly (it becomes about 20-30 KB/s) and RX error counter blows up. There are like 50-100 errors per second.

ifconfig output

Sometimes even FileZilla connection is lost giving a "Corrupt Packet" error and about a few seconds later it resumes the transfer.


I checked the 50MHz clock into the PHY and it seems fine.

I tried lowering the display refresh rate, but still the errors occur however slightly less.

I should also mention that when I adjust ethernet speed as 10 Mbps and half-duplex, there are no more errors and transfer speed is around 800 KB/s.


From "imx6ul.dtsi" file I see that LCD and FEC1 are on the same processor bus (that is "aips2" bus). Could this be the result of bus contention due to heavy LCD load? Is there a way to see the bus usage? Is there a similar issue in EVK boards?