linux-kernel - Re: [PATCH v4 4/8] dt-bindings: PCI: dwc: Add dma-ranges, region mask

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Message-ID: <20230317183037.GB2445959-robh@kernel.org>
Date:   Fri, 17 Mar 2023 13:30:37 -0500
From:   Rob Herring <robh@...nel.org>
To:     Elad Nachman <enachman@...vell.com>
Cc:     thomas.petazzoni@...tlin.com, bhelgaas@...gle.com,
        lpieralisi@...nel.org, kw@...ux.com,
        krzysztof.kozlowski+dt@...aro.org, linux-pci@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 4/8] dt-bindings: PCI: dwc: Add dma-ranges, region mask

On Mon, Mar 13, 2023 at 02:40:12PM +0200, Elad Nachman wrote:
> From: Elad Nachman <enachman@...vell.com>
> 
> Add properties to support configurable DMA mask bits and region mask bits:
> 
>  1. configurable dma-ranges is needed for Marvell AC5/AC5X SOCs which
>     have their physical DDR memory start at address 0x2_0000_0000.
> 
>  2. Configurable region mask bits is needed for the Marvell Armada
>     7020/7040/8040 SOCs when the DT file places the PCIe window above the 4GB region.
>     The Synopsis Designware PCIe IP in these SOCs is too old to specify the
>     highest memory location supported by the PCIe, but practically supports
>     such locations. Allow these locations to be specified in the DT file.
> 
> Signed-off-by: Elad Nachman <enachman@...vell.com>
> ---
> v4:
>    1) Fix commit message and its formatting
> 
>    2) Replace num-dmamask with dma-ranges
> 
>  .../devicetree/bindings/pci/snps,dw-pcie-common.yaml        | 5 +++++
>  Documentation/devicetree/bindings/pci/snps,dw-pcie.yaml     | 6 ++++++
>  2 files changed, 11 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/pci/snps,dw-pcie-common.yaml b/Documentation/devicetree/bindings/pci/snps,dw-pcie-common.yaml
> index d87e13496834..3cb9af1aefeb 100644
> --- a/Documentation/devicetree/bindings/pci/snps,dw-pcie-common.yaml
> +++ b/Documentation/devicetree/bindings/pci/snps,dw-pcie-common.yaml
> @@ -261,6 +261,11 @@ properties:
>  
>    dma-coherent: true
>  
> +  num-regionmask:
> +    description: |
> +      number of region limit mask bits to use, if different than default 32
> +    maximum: 64

This should be implied from the compatible string.

> +
>  additionalProperties: true
>  
>  ...
> diff --git a/Documentation/devicetree/bindings/pci/snps,dw-pcie.yaml b/Documentation/devicetree/bindings/pci/snps,dw-pcie.yaml
> index 1a83f0f65f19..ed7ae2a14804 100644
> --- a/Documentation/devicetree/bindings/pci/snps,dw-pcie.yaml
> +++ b/Documentation/devicetree/bindings/pci/snps,dw-pcie.yaml
> @@ -197,6 +197,12 @@ properties:
>        - contains:
>            const: msi
>  
> +  dma-ranges:
> +    description:
> +      Defines the DMA mask for devices which due to non-standard HW address
> +      assignment have their RAM starting address above the lower 32-bit region.
> +      Since this is a mask, only the size attribute of the dma-ranges is used.
> +

No need for this, it is already defined in pci-bus.yaml.

The description is wrong here anyways. The purpose is to translate 
inbound PCI addresses to parent bus addresses (and eventually CPU 
addresses).

Rob