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

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Date:   Wed, 16 Oct 2019 10:15:23 +0530
From:   Kishon Vijay Abraham I <kishon@...com>
To:     Rob Herring <robh@...nel.org>
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 16/10/19 12:12 AM, Rob Herring wrote:
> 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.

Sure Rob. Thanks for the review.

-Kishon
> 
>>
>> 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
>>