Re: [PATCH v2 RFC/RFT 1/5] ARM: dma-mapping: Add fallback normal page allocations

From: Christoph Hellwig
Date: Wed Apr 24 2019 - 15:27:14 EST

On Wed, Apr 24, 2019 at 11:33:11AM -0700, Nicolin Chen wrote:
> I feel it's similar to my previous set, which did most of these
> internally except the renaming part. But Catalin had a concern
> that some platforms might have limits on CMA range [1]. Will it
> be still okay to do the fallback internally?
> [1: ]

Catalins statement is correct, but I don't see how it applies to
your patch. Your patch just ensures that the fallback we have
in most callers is uniformly applied everywhere. The non-iommu
callers will still need to select a specific zone and/or retry
just the page allocator with other flags if the CMA (or fallback)
page doesn't match what they need. dma-direct does this correctly
and I think the arm32 allocator does as well, although it is a bit
hard to follow sometimes.