[Letux-kernel] USB3-port on OMAP5432EVM

H. Nikolaus Schaller hns at goldelico.com
Thu Feb 16 14:43:24 CET 2017

Hi Roger,
I found time to look deeper into this issue and have found it.

>> Maybe some u-boot dependency? I use a modified 2016.11.
>> Should find time do more testing...
> Yeah. might be a good idea to try different u-boot versions.
>> Is there a way to debug what dwc3 is doing or not doing?
> You can enable dwc3 trace events.
> cd /sys/kernel/debug/tracing
> echo 1 > events/dwc3/enable

well, I did not find events/dwc3 but a boot log trace of dwc3 failing.

After checking with printk if the probe function did succeed,
it turned out that the id pin in extcon-palmas did always return
-EPROBE_DEFER making the dcw3 driver finally fail to probe.

This turned out to be a disabled CONFIG_GPIO_PALMAS in our defconfig
(we do not use the omap2plus). No idea why it was disabled and why
it did work up to 4.8 or so... Maybe some detail changed in probing
sequence or dependencies.

Perhaps CONFIG_USB_DWC3_OMAP could enforce CONFIG_GPIO_PALMAS as well.

BR and thanks for suggesting to look at tracing/events which directed
me to the solution,

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