linux-kernel - Re: [RFC PATCH 02/21] dt-bindings: PCI: Endpoint: Add DT bindings for PCI EPF Device

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Date:   Tue, 15 Oct 2019 13:42:43 -0500
From:   Rob Herring <robh@...nel.org>
To:     Kishon Vijay Abraham I <kishon@...com>
Cc:     Bjorn Helgaas <bhelgaas@...gle.com>,
        Jonathan Corbet <corbet@....net>, Jon Mason <jdmason@...zu.us>,
        Dave Jiang <dave.jiang@...el.com>,
        Allen Hubbe <allenbh@...il.com>,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Mark Rutland <mark.rutland@....com>, linux-pci@...r.kernel.org,
        linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
        devicetree@...r.kernel.org, linux-ntb@...glegroups.com
Subject: Re: [RFC PATCH 02/21] dt-bindings: PCI: Endpoint: Add DT bindings
 for PCI EPF Device

On Thu, Sep 26, 2019 at 04:59:14PM +0530, Kishon Vijay Abraham I wrote:
> Add device tree bindings for PCI endpoint function device. The
> nodes for PCI endpoint function device should be attached to
> PCI endpoint function bus.
> 
> Signed-off-by: Kishon Vijay Abraham I <kishon@...com>
> ---
>  .../bindings/pci/endpoint/pci-epf.txt         | 28 +++++++++++++++++++
>  1 file changed, 28 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/pci/endpoint/pci-epf.txt

This and the previous patch for the bus should be combined and please 
convert to a schema.

> 
> diff --git a/Documentation/devicetree/bindings/pci/endpoint/pci-epf.txt b/Documentation/devicetree/bindings/pci/endpoint/pci-epf.txt
> new file mode 100644
> index 000000000000..f006395fd526
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/pci/endpoint/pci-epf.txt
> @@ -0,0 +1,28 @@
> +PCI Endpoint Function Device
> +
> +This describes the generic bindings to be used when a device has to be
> +exposed to the remote host over PCIe. The device could be an actual
> +peripheral in the platform or a virtual device created by the software.
> +
> +epcs : phandle to the endpoint controller device
> +epc-names : the names of the endpoint controller device corresponding
> +	    to the EPCs present in the *epcs* phandle

Other than the NTB case, I'd expect the parent device to be the 
controller. Let's make NTB the exception...


> +vendor-id: used to identify device manufacturer
> +device-id: used to identify a particular device
> +baseclass-code: used to classify the type of function the device performs
> +subclass-code: used to identify more specifically the function of the device

Are these codes standard?

Powerpc has "class-code" already...

> +subsys-vendor-id: used to identify vendor of the add-in card or subsystem

Powerpc has "subsystem-vendor-id" already...

> +subsys-id: used to specify an id that is specific to a vendor
> +
> +Example:
> +Following is an example of NTB device exposed to the remote host.
> +
> +ntb {

This is going to need some sort of addressing (which implies 'reg')? If 
not, I don't understand why you have 2 levels.

> +	compatible = "pci-epf-ntb";
> +	epcs = <&pcie0_ep>, <&pcie1_ep>;
> +	epc-names = "primary", "secondary";
> +	vendor-id = /bits/ 16 <0x104c>;
> +	device-id = /bits/ 16 <0xb00d>;

These have a long history in OF and should be 32-bits (yes, we've let 
some cases of 16-bit creep in).

> +	num-mws = <4>;

Doesn't this apply to more than NTB?

Can't you just get the length of 'mws-size'?

> +	mws-size = <0x100000>, <0x100000>, <0x100000>, <0x100000>;

Need to support 64-bit sizes?

> +};
> -- 
> 2.17.1
>