[BUG 5.14] arm64/mm: dma memory mapping fails (in some cases)

[Christoph Hellwig]

On Tue, Sep 21, 2021 at 12:34:10PM +0300, Mike Rapoport wrote:
> > It doesn't create any new mappings.  The only real issue is that it
> > does the wrong thing for RAM in a way that might not be noticed on
> > simple (x86/PC) platforms.
> 
> But if the mapping request was rejected by devm_ioremap_resource() because
> of an attempt to map RAM, why we would get to dma_map_resource() at all? 

dma_map_resource takes a phys_addr_t that could come from anywhere.