> 2023年2月22日 17:24，Robin Murphy <robin.murphy@xxxxxxx> 写道： [...] > > AFAICS, all you should actually need is a single self-contained addition here, something like: > > + /* > + * DT-based MIPS doesn't use OF_DMA_DEFAULT_COHERENT, but > + * might override the system-wide default at runtime. > + */ > +#if defined(CONFIG_ARCH_HAS_SYNC_DMA_FOR_DEVICE) || \ > + defined(CONFIG_ARCH_HAS_SYNC_DMA_FOR_CPU) || \ > + defined(CONFIG_ARCH_HAS_SYNC_DMA_FOR_CPU_ALL) > + is_coherent = dma_default_coherent; > +#endif That makes more sense, thanks. I’ll append CONFIG_MIPS as a condition here as well because it may break RISC-V whose dma_default_coherent is not set to true from very beginning. > >> node = of_node_get(np); >> > > Then *after* that's fixed, we can do a more comprehensive refactoring to merge the two mechanisms properly. FWIW I think I'd prefer an approach closer to the first one, where config options control the initial value of dma_default_coherent rather than architectures having to override it unconditionally (and TBH I'd also like to have a generic config symbol for whether an arch supports per-device coherency or not). Ok I’ll try to revert to the initial way. Is there any reason that an arch can’t support per-device coherency? Thanks - Jiaxun > > Thanks, > Robin.
