Issue about using the usb to serial through usb hub on imx6q

[brianwu]

Hi,

I have a imx6q customized board which connect the usb device as follow:

CPU USB HOST1 -> USB HUB(AU6259) -> USB to Serial (XR21V1410 or FT232BL)

I use the attached program to do the stress test on both usb serial ports. However, The usb driver will hang after some minutes or hours.

The system still work while the usb driver hang, but I couldn't use any usb devices via the usb hub. I have to reboot the system to let them work again.

There are some methods to accelerate the duplication:

1. Add u-boot parameter "maxcpus=0" or build non-smp kernel.

2. Add other bus loading such as i2c, spi and gpu loading.

3. Add cpu loading.

I have tested the following kernel and all of them have same issue:

1. 3.0.35 kernel on 4.0.0 BSP

2. 3,0,35 kernel on 4.1.0 BSP

3. 3.10.17_ga kernel on Freescale git server

BR

Brian

Original Attachment has been moved to: usbserialtest.c.zip

[igorpadykov]

Hi brianwu

this behaviour may point to DDR errors

(USB module uses DDR very intensively). Suggestion to

find more accurate calibration settings.

https://community.freescale.com/message/331721#331721

https://community.freescale.com/docs/DOC-96412

For test, one can try to use lower operating frequency (processor and DDR).

Best regards

chip

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[brianwu]

I have tried to decease CPU frequency to 396MHz and DDR frequency to 400MHz, but this issue still happen.

I have done some test:

1. I rework a board to connect the "CPU USB HOST1" to "USB to Serial(XR21V1410)" directly and the board has already run for one day without any hang issue.

2. After enable the usb kernel debug message, the issue will be not easy to duplicate. But it still couldn't solve the issue.

BR

Brian

[igorpadykov]

Hi brianwu

suggest to try other usb hub.

Also one can check power supplies for this hub

(are they good filtered) and check layout of its signal lines (

signal integrity and noise) of hub connections.

This may narrow down problem.

Also one can try latest BSP, below

L3.10.17_1.0.0_IMX6QDLS_BUNDLE

Best regards

chip

[Danube]

Hi Chip,

Do you have any suggest Hub Vender to us ?

OR

Do you have any AVL list share to us ?

[igorpadykov]

Hi Apollo

no specific suggestions.

Best regards

chip

[brianwu]

Hi,

I don't think the problem is due to the DDR error and I had already used the ddr stress test tool before.

If the issue is caused by DDR error, the error will be random. And it should be more easily to duplicate in the SMP kernel

because the system will use the DDR more frequently.

BR

Brian