Re: [RFC 2/5] dt-bindings: brcm: Add reserved-dma-region for iPROC

[Robin Murphy <robin.murphy-5wv7dgnIgG8@public.gmane.org>]

On 06/03/18 04:59, Jitendra Bhivare wrote:
> With SoC wide DMA mask of 40-bit, the mappings for entire IOVA space can't
> be specified in the PAXBv2 PCIe RC of SoC. The holes in IOVA space needs to
> be reserved to prevent any IOVA allocations in those spaces.

Can you clarify why? If this is the PCI inbound window thing again, let 
me say once again that "dma-ranges" is the appropriate way for DT to 
describe the hardware.

Robin.

> reserved-dma-region property is added to specify the ranges which should
> never be mapped and given to devices sitting behind.
> 
> Reviewed-by: Ray Jui <ray.jui-dY08KVG/lbpWk0Htik3J/w@public.gmane.org>
> Reviewed-by: Vikram Prakash <vikram.prakash-dY08KVG/lbpWk0Htik3J/w@public.gmane.org>
> Reviewed-by: Scott Branden <scott.branden-dY08KVG/lbpWk0Htik3J/w@public.gmane.org>
> Signed-off-by: Jitendra Bhivare <jitendra.bhivare-dY08KVG/lbpWk0Htik3J/w@public.gmane.org>
> ---
>   Documentation/devicetree/bindings/pci/brcm,iproc-pcie.txt | 3 +++
>   1 file changed, 3 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/pci/brcm,iproc-pcie.txt b/Documentation/devicetree/bindings/pci/brcm,iproc-pcie.txt
> index b8e48b4..3be0fe3 100644
> --- a/Documentation/devicetree/bindings/pci/brcm,iproc-pcie.txt
> +++ b/Documentation/devicetree/bindings/pci/brcm,iproc-pcie.txt
> @@ -30,6 +30,9 @@ Optional properties:
>   - dma-ranges: Some PAXB-based root complexes do not have inbound mapping done
>     by the ASIC after power on reset.  In this case, SW is required to configure
>   the mapping, based on inbound memory regions specified by this property.
> +- reserved-dma-region: PAXBv2 with IOMMU enabled cannot provide mappings for
> +  entire IOVA space specified by DMA mask. Hence this is used to reserve the
> +  gaps in dma-ranges.
>   
>   - brcm,pcie-ob: Some iProc SoCs do not have the outbound address mapping done
>   by the ASIC after power on reset. In this case, SW needs to configure it
>