Why do I have Rx Fifo overrun on uarts when I plugged USB 3 key in IMX6Q ?

[alexisfronteau]

Hi,

I have an Imx6q collecting several sensors data on differents uarts. It works fine but I have overrun on received data when I plugged an USB3 key : 

   [2454.926806] usb 3-1: new SuperSpeed USB device number 3 using xhci_hcd
   [2454.933404] imx-uart 21f0000.serial: Rx FIFO overrun
   [ 2454.938476] imx-uart 21f4000.serial: Rx FIFO overrun
   [ 2454.943501] imx-uart 21f0000.serial: Rx FIFO overrun

   [ 2454.967902] usb 3-1: Parent hub missing LPM exit latency info. Power management will be impacted.
   [ 2454.982832] usb-storage 3-1:1.0: USB Mass Storage device detected
   [ 2454.992439] scsi2 : usb-storage 3-1:1.0

   [ 2455.997278] scsi 2:0:0:0: Direct-Access Corsair Voyager GS 000A PQ: 0 ANSI: 6
   [ 2456.009700] sd 2:0:0:0: [sdb] 123600896 512-byte logical blocks: (63.2 GB/58.9 GiB)
   [ 2456.017918] sd 2:0:0:0: [sdb] Write Protect is off
   [ 2456.023235] sd 2:0:0:0: [sdb] Write cache: disabled, read cache: enabled, doesn't support DPO or FUA
   [ 2456.084890] sdb: sdb1
   [ 2456.090274] sd 2:0:0:0: [sdb] Attached SCSI removable disk

I would like to know if there are some way connected and if I can do something to avoid this issued. (I work with the linux 3.14 kernel)

Thanks

[igorpadykov]

Hi Alexis

Rx Fifo overrun may occur due to bus loading problems caused by usb module

(as it can consume much bus bandwidth). One can try to use uart flow controls

to avoid overruns. May be useful to check bus loading with mmdc profile tool

MMDC Profiling Tool 

Best regards
igor
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