g_mass_storage device dependency on HW?

[danmacdonald]

My device needs to auto-mount to a PC as a USB mass storage device.

I have implemented a partition for user data on my device, formatted it to fat, and launch the g_mass_storage.ko driver:

modprobe g_mass_storage file=/dev/mmcblk2p3 removable=1‍

The drive successfully mounts as a USB Mass Storage device on some PCs. BUT on some other PCs the device is NOT recognized. I have narrowed down the culprit as a possible HW dependency, here's why:

1) Plug IMX into Windows PC "A". auto-mount is successful

2) Plug IMX into Ubuntu PC "B". auto-mount is successful

3) Plug IMX into Windows PC "C". auto-mount is NOT successful

4) Boot PC "C" into Ubuntu. IMX auto-mount is NOT successful  --> Therefore, not a silly Windows driver issue

Now Add a Cheap USB hub in between the PC and IMX (IMX-->USB HUB---> PC)

5) Plug IMX -->USB HUB --> Ubuntu PC "C" . auto-mount is successful !!!

6) Boot PC "C" into Windows again. Plug IMX -->USB HUB --> Windows PC "C" . auto-mount is successful !!!

Here is my IMX output when modprobing:

# modprobe g_mass_storage file=/dev/mmcblk2p3 removable=1
[ 1441.573884] Number of LUNs=8
[ 1441.580845] Mass Storage Function, version: 2009/09/11
[ 1441.586390] LUN: removable file: (no medium)
[ 1441.596948] Number of LUNs=1
[ 1441.603800] LUN: removable file: /dev/mmcblk2p3
[ 1441.609030] Number of LUNs=1
[ 1441.618926] g_mass_storage gadget: Mass Storage Gadget, version: 2009/09/11
[ 1441.626486] g_mass_storage gadget: userspace failed to provide iSerialNumber
[ 1441.634116] g_mass_storage gadget: g_mass_storage ready‍‍‍‍‍‍‍‍‍‍

The output when it successfully mounts:

[ 2696.409919] g_mass_storage gadget: high-speed config #1: Linux File-Backed Storage‍

When mounted to PC "A" the VID, PID, Rev are:

VID 0x0525 - driver default

PID 0xA4A5 - driver default

REV 0x0314 

I'd like to fix this, but I'm at a loss of how to do this if its a HW dependency.

[b36401]

I can suggest to check precisely the voltage of USB signal.
Possibly the voltage is a bit out of range and some hosts fail to connect but USB hub fixes it.

Have a great day,
Victor

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[danmacdonald]

The USB HUB in testing is NOT powered, so I don't think that is the cause