IMX8MQ EVK getting USB hub message "Cannot enable. Maybe the USB cable is bad?"

[hiteshviradiya]

Dear Experts,

We are designing a product based on imx8mq SoC . And I am doing some PoC on imx8mq EVK.

While connecting multiple USB slaves on IMX8MQ EVK via USB HUB (from Microchip), We are getting "Cannot enable. Maybe the USB cable is bad?" prints frequently.

What does it mean?

I believe something is related to slave's enumeration but can't locate it exactly and can't find the culprit. Below are the slaves I am testing with USB Hub:

1) USB to Ethernet converter (LAN7800EVB)

2) 2 Sierra (or various combinations of) USB Modems

Any input is highly appreciated to debug this issue further.

[hiteshviradiya]

Thanks Igor !

There is a long way to receive our custom board but we want to make sure we test different use cases (which we are supposed to test on our custom board) on EVK. Also while connecting Mictochip's USB Hub (USB5734 and/or USB5807) to USB port of EVK, it got detected twice ! 

[    2.206618] usb 1-1: New USB device found, idVendor=0424, idProduct=2807
[    2.213406] usb 1-1: New USB device strings: Mfr=1, Product=2, SerialNumber=0
[    2.220676] usb 1-1: Product: USB2807 Hub
[    2.224818] usb 1-1: Manufacturer: Microchip
[    2.232872] caam_jr 30901000.jr0: Instantiated RNG4 SH0.
[    2.254427] hub 1-1:1.0: USB hub found
[    2.258397] hub 1-1:1.0: 7 ports detected
[    2.300727] Can't support > 32 bit dma.
[    2.301470] Can't support > 32 bit dma.
[    2.310189] usb 2-1: new SuperSpeed USB device number 2 using xhci-hcd
[    2.321711] usbcore: registered new interface driver usbhid
[    2.321713] usbhid: USB HID core driver
[    2.322636] usb 2-1: New USB device found, idVendor=0424, idProduct=5807
[    2.322642] usb 2-1: New USB device strings: Mfr=1, Product=2, SerialNumber=0
[    2.322647] usb 2-1: Product: USB5807 Hub
[    2.322651] usb 2-1: Manufacturer: Microchip
[    2.366442] hub 2-1:1.0: USB hub found
[    2.366489] hub 2-1:1.0: 7 ports detected

I know the fact it is enumeration between slave (USB hub) & master (IMX8), I have less doubt on IMX8 kernel but when I connect it to my PC (x86 Ubutnu), it got detected only one time.

Your inputs are always valuable, waiting for your input.

--

Thanks,

Hitesh

[hiteshviradiya]

Hi Igor,

Any inputs on my next question?

--

Thanks,

Hitesh

[igorpadykov]

Hi Hitesh

if you do not see issue with USB typeC connector seems "e11176"

is not applicable.

"got detected twice" isue is related to poor signal/cable.

Best regards
igor

[hiteshviradiya]

Hi Igor,

In that case, I can't see duplicate detection in my x86 PC. I am using same cable and same HUB PCB.

But I don't see such things on my host PC. Why ??

--

Thanks,

Hitesh

[igorpadykov]

Hi Hitesh

because host PC has different board layout/material and its

signal characteristics are different compared with EVK.

Best regards
igor

[hiteshviradiya]

Hi Igor,

Does this mean EVK has poor layout/material and its signal characteristics are weak?

Then why can we doubt on cable quality (poor cable ?? !!)

How come this is possible?

--

Thanks,

Hitesh

[igorpadykov]

Hi Hitesh

it is not poor, but sufficient for demonstrating as much as

possible processor characteristics on EVK. To avoid above issues

one can design custom board paying more attention to usb layout,

so usb signals quality can be better on custom board.

Best regards
igor

[igorpadykov]

Hi Hitesh

one can try to fully recompile image for custom board. Also

issue may be related to poor cable ot power supplies as mentioned on below links

[Solved] USB Hub - Cannot enable. Maybe the USB cable is bad? / Kernel & Hardware / Arch Linux Forum... 

[SOLVED] usb 1-1-port8: Cannot enable. Maybe the USB cable is bad? 

Best regards
igor
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[hiteshviradiya]

Hi Igor,

Another important observation:

If I connect same external HUB w/ all the connected USB slaves to USB typeC connector (via type-C male to USB female cable), I don't see either of these 2 issues reported !!!!!!

1) No such "Cannot enable. Maybe the USB cable is bad?" prints

2) No duplicate or twice detection of USB hub happens.

So what is difference in EVK on USB Type-C and normal USB port?

Now it looks like something is wrong with USB Host of IMX8 EVK.

Please highlight on this because our product has a lot of peripherals / connections via USB Host and our product's main usecase is running via USB Host of SoC. Missing a little bit will create risk on our future product.

--

Thanks,

Hitesh

[igorpadykov]

Hi Hitesh

>If I connect same external HUB w/ all the connected USB slaves to USB typeC connector
>(via type-C male to USB female cable), I don't see either of these 2 issues reported !!!!!!

it may be explained in the same way - issue may be related to poor cable ot power supplies as

suggested on above links. USB Type-C has better layout, less noise, more strong signal than

on normal USB port.

Best regards
igor

[hiteshviradiya]

I am reporting 2 issues ! Not only "Cannot enable. Maybe the USB cable is bad?" but also "duplicate or twice detection of USB hub" and I saw IMX8 ERRATA (IMX8MDQLQ_0N14W.pdf) file and found that "e11176: USB: USB 3.0 Host Hot Plug incorrectly enumerates"

Is it related to what I am facing both the issues?

--

Thanks,

Hitesh