Android 7 Host on iMX7D - USB Auto-suspend Issue for Modem Peripheral

[sushant]

We have a LTE Modem peripheral connected over USB to iMX7D host. Host is running Android OS 7.1.2r9. 

There are two types of Suspend-Resume/Wakeup:

- Host to Modem Resume (working as expected)

- Modem to Host Wakeup (has an issue, please read on)

According to the Modem vendor, in a working case of Modem to Host Wakeup:  K state gets initiated and is maintained by modem for 5ms, following which within 500us Host takes over and maintains K state for rest of the 20ms. 
However on most occasions, the K state initiated by Modem for 5ms, however the Host does not maintain the K state completing the 20ms. Thus Auto-suspend does not work as expected.

USB Analyzer analysis is attached.

[sushant]

Hi Igor,

Thanks for the response. Which mode you are referring to that is not supported? However I am a bit concerned now, because I would expect NXP Host to be USB2.0 standards compliant. Can you please clarify?

Also the imx7DRM document you shared doesn't have the section you listed

The imx7DRM document you shared http://cache.nxp.com/files/32bit/doc/ref_manual/IMX7DRM.pdf has:

11.4.4.3.3 Suspend/Resume-Host Operational Model

Which does mention a 20ms period for which the Host delays port resume time. Are you saying Host does not drive K-state during this period?

[igorpadykov]

Hi Sushant

seems software BSP does not support this mode (meaning that not all features described in

Reference Manual are implemented in software), software supports modes described in Linux Manual

sect.4.9.7 USB Wakeup Usage. One can add additional software features himself or apply for help to

NXP Professional Services which helps with software customizations

NXP Professional Services | NXP 

Best regards
igor

[sushant]

Hi Igor,

I am wondering if we referring to the same version of documents? There are only 10 chapters in Linux Manual. In the DRM document, 11.5.2 is the last section. I am not sure which document you are referring to that has 11.5.3xx section

- Sushant

[igorpadykov]

Hi Sushant

sorry, it is sect.4.9.7 USB Wakeup Usage attached Linux Manual.

Best regards
igor

[sushant]

Hi Igor,

Thanks, but this raises a concern for me.

Can you please provide me details of VBUS and ID based implementation of Resume? We can then look into how to implement the same in Hardware/Drivers.

Also, I am not sure how is NXP BSP's USB suspend-resume is standards compliant. K-state transition wake up is defined as the method in standards for Resume. Is it possible for OEMs to alter the BSP such as to support K-state based Resume/Wakeup? Or is it not supported by USB IP?

- Sushant

[igorpadykov]

Hi Sushant

could you please try to reproduce issue on NXP i.MX7D EVK reference board

with Demo Images from

i.MX Software | NXP 

for testing one can use unit tests (folder /mxc_usb_test)

http://www.nxp.com/lgfiles/NMG/MAD/YOCTO/imx-test-5.7.tar.gz 

If you think that there are issues in i.MX7 usb hardware module one can check

usb sertification documents on link below, test "A4.8: A-UUT Suspend/Resume/Reset timing"

in Freescale Semiconductor_MCIMX7D_Pass_Test_Report_20160627_formal.pdf document

is marked as "Passed".

i.MX 7Dual/Solo USB Certification Quick Guide 

Best regards
igor

[igorpadykov]

Hi Sushant

I am afraid this mode is not supported in NXP software BSPs, supported

modes are described in sect.4.9.7 USB Wakeup Usage attached Linux Manual.

Sect.11.5.3.3.2.1 Host Mode Events i.MX7D Reference Manual describes what

wake modes are supported by hardware (i.MX7D USB module),

http://cache.nxp.com/files/32bit/doc/ref_manual/IMX7DRM.pdf

Best regards
igor
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