On Thu, Mar 6, 2014 at 9:44 PM, Santosh Shilimkar <santosh.shilimkar@xxxxxx> wrote: > On Friday 07 March 2014 11:13 AM, Rob Herring wrote: >> On Thu, Mar 6, 2014 at 3:19 AM, Santosh Shilimkar >> <santosh.shilimkar@xxxxxx> wrote: >>> The of_dma_is_coherent() helper parses the given DT device >>> node to see if the "dma-coherent" property is supported and >>> returns true or false accordingly. >>> >>> For the architectures which are fully dma coherent and don't need per device >>> property, it can enable CONFIG_ARCH_IS_DMA_COHERENT config option which >>> enables DMA coherent for all devices by default. >> >> This worries me. I killed off arch_is_coherent() for arm. Now we're >> adding something back. Also, we already have HAVE_GENERIC_DMA_COHERENT >> which is different, but the names will be confusing. MIPS also has >> DMA_NONCOHERENT. >> > Thanks for comments Rob. I will address them in next version. > Specifically about ARCH_IS_DMA_COHERENT, I wasn't very comfortable either > while adding it. But as Arnd mentioned, there is a need to have a way > for the arch's which are fully coherent to use coherent ops by default. > > Am not sure whats the best way to have such support without imposing > any special updates on such arches. Thinking about this some more, if the arch is always coherent or always non-coherent, then the default ops are always fine. In that case set_arch_dma_coherent_ops is always a nop and of_dma_is_coherent is a don't care. Rob -- 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
