Unused USB_OTG1_OC and USB over-current events

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Unused USB_OTG1_OC and USB over-current events

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uthappapj
Contributor II

Hello,

        Our target platform has a i.MX6ULZ SoC running in it. Upon using the USB OTG interface in "host" role for attaching USB digital headsets (e.g., Google Pixel USB-C earbuds) we observed the following Linux kernel error messages being reported:

kern.err kernel: usb usb1-port1: over-current condition
kern.inf kernel: usb 1-1: USB disconnect, device number 2

        After some investigation into the problem, we discovered that on our target platform the USB_OTG1_OC signal had been left unconnected. Also, we came across information in the Linux kernel documentation, that we may have to use the flag "disable-over-current" in the USB OTG1 device node in the device tree specification for our target. Like so:

&usbotg1 {
dr_mode = "otg";
pinctrl-names = "default";
pinctrl-0 = <&pinctrl_usb_otg1>;
disable-over-current;
status = "okay";
};

        After adding the above change. The USB over-current event stopped appearing. And the USB interface also seems to function normally. We further checked the health of the USB interface using a multi-meter to check if we had wrongly suppressed any real/actual USB over-current situation. But it did not seem to be the case.

        So my query is, whether the solution to use the flag "disable-over-current" the way it's described above, the right way to handle the H/W design we have? Is there anything else that needs to be looked into to ensure that the USB works safely and correctly?

Best regards,

Uthappa

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igorpadykov
NXP Employee
NXP Employee

Hi Uthappa

 

> my query is, whether the solution to use the flag "disable-over-current" the way it's

>described above, the right way to handle the H/W design we have?

 

yes it is correct, in nxp dts file such "disable-over-current" is also used:

https://source.codeaurora.org/external/imx/linux-imx/tree/arch/arm/boot/dts/imx6ul-14x14-evk.dtsi?h=...

 

Best regards
igor

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uthappapj
Contributor II

 

        Thank you for confirming this Igor!

-Uthappa

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igorpadykov
NXP Employee
NXP Employee

Hi Uthappa

 

> my query is, whether the solution to use the flag "disable-over-current" the way it's

>described above, the right way to handle the H/W design we have?

 

yes it is correct, in nxp dts file such "disable-over-current" is also used:

https://source.codeaurora.org/external/imx/linux-imx/tree/arch/arm/boot/dts/imx6ul-14x14-evk.dtsi?h=...

 

Best regards
igor

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