On Fri, Feb 28, 2014 at 6:00 PM, Arnd Bergmann <arnd@xxxxxxxx> wrote: > On Thursday 27 February 2014 16:17:50 Santosh Shilimkar wrote: >> diff --git a/arch/arm/kernel/devtree.c b/arch/arm/kernel/devtree.c >> index f751714..926b5dd 100644 >> --- a/arch/arm/kernel/devtree.c >> +++ b/arch/arm/kernel/devtree.c >> @@ -235,3 +238,61 @@ const struct machine_desc * __init setup_machine_fdt(unsigned int dt_phys) >> >> return mdesc; >> } >> + >> +void arm_dt_dma_configure(struct device *dev) >> +{ >> + dma_addr_t dma_addr; >> + phys_addr_t paddr, size; >> + dma_addr_t dma_mask; >> + int ret; >> + >> + /* >> + * if dma-ranges property doesn't exist - use 32 bits DMA mask >> + * by default and don't set skip archdata.dma_pfn_offset >> + */ >> + ret = of_dma_get_range(dev->of_node, &dma_addr, &paddr, &size); >> + if (ret == -ENODEV) { >> + dev->coherent_dma_mask = DMA_BIT_MASK(32); >> + if (!dev->dma_mask) >> + dev->dma_mask = &dev->coherent_dma_mask; >> + return; >> + } > > I think this is a reasonable default, but I also want Russell's > opinion on this, since I suspect he will argue that we shouldn't > default to setting a DMA mask for devices that are not DMA capable. of_platform_device_create_pdata() in drivers/of/platform.c does the same assumption since ages. > Maybe someone has an idea how we can detect all three important cases: > > a) A device is marked as DMA capable using a dma-ranges property > b) A device is known not to be DMA capable > c) we don't have any dma-ranges properties in an old dtb file > but still want 32 bit masks by default. The exact same solution would apply to the of core right? Yours, Linus Walleij -- 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