[RFC 3/5] dma-mapping: Enable global non-coherent pool support for RISC-V

[Rob Herring]

On Fri, Jul 23, 2021 at 3:40 PM Atish Patra <atish.patra at wdc.com> wrote:
>
> Currently, linux,dma-default is used to reserve a global non-coherent pool
> to allocate memory for dma operations. This can be useful for RISC-V as
> well as the ISA specification doesn't specify a method to modify PMA
> attributes or page table entries to define non-cacheable area yet.
> A non-cacheable memory window is an alternate options for vendors to
> support non-coherent devices. "dma-ranges" must be used in conjunction with
> "linux,dma-default" property to define one or more mappings between device
> and cpu accesible memory regions.

'dma-ranges' applies to buses. And, well, maybe devices when the bus
is not well defined. It is not a reserved-memory property.

Rob