On Wed, Jun 29, 2022 at 09:38:00AM +1200, Michael Schmitz wrote: > That's one of the 'liberties' I alluded to. The reason I left these in is > that I'm none too certain what device feature the DMA API uses to decide a > device isn't cache-coherent. The DMA API does not look at device features at all. It needs to be told so by the platform code. Once an architecture implements the hooks to support non-coherent DMA all devices are treated as non-coherent by default unless overriden by the architecture either globally (using the global dma_default_coherent variable) or per-device (using the dev->dma_coherent field, usually set by arch_setup_dma_ops). > If it's dev->coherent_dma_mask, the way I set > up the device in the a3000 driver should leave the coherent mask unchanged. > For the Zorro drivers, devices are set up to use the same storage to store > normal and coherent masks - something we most likely want to change. I need > to think about the ramifications of that. No, the coherent mask is slightly misnamed amd not actually related.
