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Last Post 22 Feb 2019 01:50 PM by  Joshua Pagnotta
DM3730 USB OTG with 1.1 Speed Storage
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Joshua Pagnotta
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22 Feb 2019 01:50 PM

    I am having issues when attempting to transfer a file to a storage device connected to the USB OTG port running at "full speed (1.1)". The drive shows up correctly when it is connected to the system and I am able to view the files that reside on this drive. When I attempt to move a file from the rootfs to the external storage drive everything connected to the USB OTG is disconnected and does not recover. This happens every time for USB 1.1 storage. The same attempt with a USB 2.0 storage device works without fail.

    I eventually was able to get this use case working when I enabled DMA (unchecked "Disable DMA (always use PIO)") with mentor workaround however this breaks the other use-case for this port which is a USB to Ethernet adapter. If DMA is enabled I can no longer receive packets via the USB to Ethernet adapter, transmitting works fine.

    Since we never have both the USB to Ethernet adapter and the USB 1.1 storage device connected at the same time I attempted to change the musb-hdrc kernel module to be a loadable module instead of built in to the kernel. This would allow me to dynamically load musb-hdrc with DMA when I need to communicate to the USB 1.1 storage and without DMA for every other use case. Unfortunately, I have been unsuccessful in getting the musb-hdrc module to load in this way. I get an error when running 'modprobe musb_hdrc' of "No such device".

    Has anyone had issues connecting USB 1.1 storage to the USB OTG port or had success at dynamically loading the musb-hdrc kernel module instead of having it built into the kernel?

    Really, I would be able to make this work if I could do any of the below:

    • Get USB 1.1 storage to work on the USB OTG port with DMA disabled
    • Get the USB to Ethernet adapter to work with DMA enabled
    • Get the musb-hdrc kernel module to dynamically load during operation so I can load it with or without DMA at any given time. Wondering if I'm missing some step to apply power to the USB OTG port that happens automatically when it's installed in the kernel.

    We are currently running with BSP version 2.4-4.

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