On Thursday 27 February 2014 16:17:49 Santosh Shilimkar wrote: > + > +/** > + * of_dma_is_coherent - Check if device is coherent > + * @np: device node > + * > + * It returns true if "dma-coherent" property was found > + * for this device in DT. > + */ > +bool of_dma_is_coherent(struct device_node *np) > +{ > + struct device_node *node = np; > + > + while (node) { > + if (of_property_read_bool(node, "dma-coherent")) { > + of_node_put(node); > + return true; > + } > + node = of_get_next_parent(node); > + } > + return false; > +} > +EXPORT_SYMBOL_GPL(of_dma_is_coherent); > This won't work on architectures that are always coherent and did not need 'dma-coherent' properties before, such as IBM Power servers. That said, I think the property makes sense, and we already have platforms using it (highbank is the one I'm aware of). We probably need ways to override this function in both ways: "always coherent" (powerpc, x86), and "never coherent" (keystone without LPAE) from platform code, and it would be nice to put either option into DT in a global location as well. We may have to go through a few iterations of this patch to get the best algorithm, but I think the interface is good at least. Arnd -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html