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.
