[PATCH] powerpc/iommu: bypass DMA APIs for coherent allocations for pre-mapped memory

[Donet Tom]

On Fri, 07 Nov 2025 10:11:05 -0600, Gaurav Batra wrote:
> Leverage ARCH_HAS_DMA_MAP_DIRECT config option for coherent allocations as
> well. This will bypass DMA ops for memory allocations that have been
> pre-mapped.
> 
> Always set device bus_dma_limit when memory is pre-mapped. In some
> architectures, like PowerPC, pmemory can be converted to regular memory via
> daxctl command. This will gate the coherent allocations to pre-mapped RAM
> only, by dma_coherent_ok().
> 
> [...]

Even though this patch is now merged. But FWIW, I had verified this on my
system and it fixed the iommu_alloc failure problem for me. So

Tested-by: Donet Tom <donettom at linux.ibm.com>

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2.52.0