linux-kernel - Re: [PATCH v5 1/3] PCI: Add DT binding for tango PCIe controller

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Date:   Thu, 8 Jun 2017 00:34:49 +0200
From:   Mason <slash.tmp@...e.fr>
To:     Rob Herring <robh@...nel.org>
Cc:     Marc Gonzalez <marc_gonzalez@...madesigns.com>,
        Bjorn Helgaas <helgaas@...nel.org>,
        Marc Zyngier <marc.zyngier@....com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Robin Murphy <robin.murphy@....com>,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Liviu Dudau <liviu.dudau@....com>,
        David Laight <david.laight@...lab.com>,
        linux-pci <linux-pci@...r.kernel.org>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        Thibaud Cornic <thibaud_cornic@...madesigns.com>,
        Phuong Nguyen <phuong_nguyen@...madesigns.com>,
        LKML <linux-kernel@...r.kernel.org>,
        DT <devicetree@...r.kernel.org>
Subject: Re: [PATCH v5 1/3] PCI: Add DT binding for tango PCIe controller

Hello Rob,

On 07/06/2017 23:29, Rob Herring wrote:
> On Wed, May 31, 2017 at 03:30:26PM +0200, Marc Gonzalez wrote:
>> Binding for the Sigma Designs SMP8759 SoC.
>>
>> Signed-off-by: Marc Gonzalez <marc_gonzalez@...madesigns.com>
>> ---
>>  Documentation/devicetree/bindings/pci/tango-pcie.txt | 30 ++++++++++++++++++++++++++++++
>>  1 file changed, 30 insertions(+)
>>
>> diff --git a/Documentation/devicetree/bindings/pci/tango-pcie.txt b/Documentation/devicetree/bindings/pci/tango-pcie.txt
>> new file mode 100644
>> index 000000000000..35ef2c811a27
>> --- /dev/null
>> +++ b/Documentation/devicetree/bindings/pci/tango-pcie.txt
>> @@ -0,0 +1,30 @@
>> +Sigma Designs Tango PCIe controller
>> +
>> +Required properties:
>> +
>> +- compatible: "sigma,smp8759-pcie"
>> +- reg: address/size of PCI configuration space, address/size of register area
>> +- device_type: "pci"
>> +- #size-cells: <2>
>> +- #address-cells: <3>
>> +- msi-controller
>> +- ranges: translation from system to bus addresses
>> +- interrupts: spec for misc interrupts, spec for MSI
>> +
>> +http://elinux.org/Device_Tree_Usage#PCI_Address_Translation
>> +http://elinux.org/Device_Tree_Usage#Advanced_Interrupt_Mapping
> 
> Why are these here?

I found these references very helpful when writing the node.
Where would you put them? In the example?

> There's several standard properties you are missing like bus-range.

My reasoning for omitting "bus-range" was that the PCI core computes
it by itself (1M per "bus" so SZ_4M => 4 devices). I thought redundant
information was bad form?

> Build your dts with "W=2". dtc recently gained some checks for PCI 
> bindings.

I'll give it a try. Did v4.9 already support it?

>> +Example:
>> +
>> +	pcie@...00 {
>> +		compatible = "sigma,smp8759-pcie";
>> +		reg = <0x50000000 SZ_4M>, <0x2e000 0x100>;
>> +		device_type = "pci";
>> +		#size-cells = <2>;
>> +		#address-cells = <3>;
>> +		msi-controller;
>> +		ranges = <0x02000000 0x0 0x00400000  0x50400000  0x0 SZ_60M>;
> 
> I don't think SZ_60M exists or is available to dts files. Just put the 
> number in.

I #defined it at the top of my DTS.
Using symbolic constants in DTS is not acceptable?

Thanks for having a look.

Regards.