[PATCH] riscv: make ZONE_DMA32 optional

[Christoph Hellwig]

On Tue, Aug 27, 2024 at 02:36:11PM +0300, Vladimir Kondratiev wrote:
> It is not necessary any RISCV platform has ZONE_DMA32.

That is an odd statement.  The point of ZONE_DMA32 is to make sure
that drivers can always allocate 32-bit DMAable memory, and without
ZONE_DMA32 that is very hard to provide unless you always have an
IOMMU.

> Example - if platform has no DRAM in [0..4G] region,
> it will report failure like below each boot.

ZONE_DMA32 is supposed to contain the 32-bit dma addressable memory,
not 32-bit physical.

Take a look at the changes that just went into Linus' tree for that.