Instantiating the sm501 OHCI subdevice results in a kernel warning.
sm501-usb sm501-usb: SM501 OHCI
sm501-usb sm501-usb: new USB bus registered, assigned bus number 1
WARNING: CPU: 0 PID: 1 at ./include/linux/dma-mapping.h:516
ohci_init+0x194/0x2d8
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