Re: [PATCH] PCI: dwc: rcar-gen4: Use 4K EPC BAR alignment

[Niklas Cassel]

On Thu, Mar 05, 2026 at 10:54:39AM +0900, Koichiro Den wrote:
> R-Car S4 Series (R8A779F[4-7]*) uses a 4K minimum iATU region size
> (CX_ATU_MIN_REGION_SIZE = 4K) as per R19UH0161EJ0130 Rev.1.30.
> 
> Update the advertised alignment to 4K, as described in
> commit 2a9a801620ef ("PCI: endpoint: Add support to specify alignment
> for buffers allocated to BARs").
> 
> With the previous 1MB alignment requirement, iATU programming for BAR4
> on this platform often cannot be performed, since a 1MB-aligned target
> address may fall outside the tiny 256B BAR4 window.

You could also mention that CX_ATU_MIN_REGION_SIZE can configured to
a value in range 4 kB to 64 kB, so 1 MB is clearly bogus.

Reviewed-by: Niklas Cassel <cassel@xxxxxxxxxx>