SYM_CONF_DMA_BOUNDARY
pn = rounddown2(pe - 1, SYM_CONF_DMA_BOUNDARY);
if (bus_dma_tag_create(np->bus_dmat, 1, SYM_CONF_DMA_BOUNDARY,
BUS_SPACE_MAXSIZE_32BIT, SYM_CONF_MAX_SG, SYM_CONF_DMA_BOUNDARY,