dma_coherent_ok
bool dma_coherent_ok(struct device *dev, phys_addr_t phys, size_t size);
if (page && !dma_coherent_ok(dev, page_to_phys(page), size)) {
if (dma_coherent_ok(dev, page_to_phys(page), size) &&
&& !dma_coherent_ok(dev, page_to_phys(page), size)) {
page = dma_alloc_from_pool(dev, size, &ret, gfp, dma_coherent_ok);
dma_coherent_ok);