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iMX6 Hang during boot without UART cable connected

Question asked by kal on Feb 16, 2017

Is there a known issue with an iMX6 boot process hanging due to the UART? I have an intermittent problem on some boards where they only boot part-way until a UART cable is physically plugged in.

 

They will spit out some Rx FIFO overrun errors for a while and then hang, e.g. here the bootup hung until a UART cable was connected 12 minutes later, at which point udevd etc started up:

 

[ 2.825049] imx-uart 21e8000.serial: Rx FIFO overrun
[ 3.584013] imx-uart 21e8000.serial: Rx FIFO overrun
[ 3.599746] imx-uart 21e8000.serial: Rx FIFO overrun
[ 3.612704] imx-uart 21e8000.serial: Rx FIFO overrun
[ 3.629967] imx-uart 21e8000.serial: Rx FIFO overrun
[ 3.652768] imx-uart 21e8000.serial: Rx FIFO overrun
[ 746.789572] udevd[156]: starting version 182
[ 746.795362] imx-uart 21e8000.serial: Rx FIFO overrun

 

I've attached a full boot dmesg, where one can see the 12 minute pause before a UART cable was physically connected. After that udevd starts, networking starts etc.

 

Many thanks

Original Attachment has been moved to: uarts.txt.zip

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