[PATCH kernel] powerpc/iommu: Report the correct most efficient DMA mask for PCI devices

[Christoph Hellwig]

On Thu, Sep 30, 2021 at 01:44:54PM +1000, Alexey Kardashevskiy wrote:
> and returns the IOMMU table mask on the pseries platform which makes some
> drivers (mpt3sas is one example) choose 32bit DMA even though bypass is
> supported. The powernv platform sort of handles it by having a bigger
> default window with a mask >=40 but it only works as drivers choose
> 63/64bit if the required mask is >32 which is rather pointless.
> 
> This reintroduces the bypass capability check to let drivers make
> a better choice of the DMA mask.
> 
> Fixes: f1565c24b596 ("powerpc: use the generic dma_ops_bypass mode")
> Signed-off-by: Alexey Kardashevskiy <aik at ozlabs.ru>

Looks good:

Reviewed-by: Christoph Hellwig <hch at lst.de>