CVMX_USBCX_GNPTXFSIZ
npsiz.u32 = cvmx_usb_read_csr32(usb, CVMX_USBCX_GNPTXFSIZ(usb->index));
cvmx_usb_write_csr32(usb, CVMX_USBCX_GNPTXFSIZ(usb->index), npsiz.u32);