Hi, just a quick question: Why is OTG disabled?  I read some "performance issues" or "high CPU usage by OTG" etc...  But can someone be more specific?

Short version of answer is: to avoid questions -  "why do we have a high load without running anything?" 

 

More specific:
http://www.cubieforums.com/index.php/topic,1084.0.html

my answer for OTG disabling on OLD  kernels :

 

any ARM kernel below 3.11 known to have a lot of harsch bugs  that make USB useless , system unstable.

so STOP use kernel 3.4.

 

- 0 read CERT allerts for OUTdated kernels

 - 0.1 most OTG bugs had been beed 2 years ago on ARM6 & 7  with kernel 3.12.x and up on rasberry PI's

  see at git //github.com/raspberrypi/linux.git for OTG armhf patches.

 

-1 update kernel

   Kick the old 3.4.x kernels of your desk and servers.

 

 use https://github.com/igorpecovnik/lib, with

KERNEL_ONLY="yes"  and KERNEL_CONFIGURE="no" 

re-enable complete USB stuff , as modules , INCLUDE OTG

 

- 2 if custom kernel modules , port them , give igor patches .

Thanks Igor for that link. Now it is clear to me.

 

remset, thank you too. I would correct your adwise to:

KERNEL_ONLY="yes"  and KERNEL_CONFIGURE="yes" //re-enable complete USB stuff , as modules , INCLUDE OTG

I am working on re-enabling OTG in mainline, I am not done so I am not sure, but I think you also need to enable OTG in script.bin, right?

I am working on re-enabling OTG in mainline, I am not done so I am not sure, but I think you also need to enable OTG in script.bin, right?

 

Mainline doesn't have script.bin any more but Device Tree which has similar role but completely different structure.

 

Sources are located in /arch/arm/boot/dts/ ... compiled under /boot/dtb

 

Documentation:

http://events.linuxfoundation.org/sites/events/files/slides/petazzoni-device-tree-dummies.pdf

Mainline doesn't have script.bin any more but Device Tree which has similar role but completely different structure.

 

Sources are located in /arch/arm/boot/dts/ ... compiled under /boot/dtb

 

Documentation:

http://events.linuxfoundation.org/sites/events/files/slides/petazzoni-device-tree-dummies.pdf

Well, interesting.

 

Any way or link to "how to enable OTG in mainline"? I have not found anything useful (for OTG) in /arch/arm/boot/dts/. I enabled needed things (later also not needed things to be sure) in .config, but that is not enough. Maybe I will find something helpful in that pdf.

Hi to All,

 

I have read this and other discussions on the USB OTG issue in old kernels but the need to use legacy kernel 3.4 and 2+ USB Hosts on Lime 2 without hub force me to test system behavior with USB0 enabled as host only (usb_port_type = 1 and usb_detect_type = 0).

 

The result is good for "high CPU usage at OTG detect enabled" phenomena. In the beginning the CPU load average is relatively high but less than 1.0.

It goes down and become close to 0 after short time without heavy system load.

 

As I read there is other "performance issues" and many bugs but the truth is that I use on A20-SOM Olimex image with kernel 3.4 for months without any problems even did not notice high the CPU load average reported by tools like top and htop.

 

My question is about other side effects, issues and instability in case of usb_port_type = 1 and usb_detect_type = 0 setup?

 

Regards

Chris