linux-kernel - Re: [RFC PATCH v12 1/5] dt-bindings: PCI: Add definition of PCIe WAKE# irq and PCI irq

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Message-ID: <CAJZ5v0iRRAQWSji0ioJ5B5M5RjbYAyb1VmuWhTZw4qy0G7_a4g@mail.gmail.com>
Date:   Sat, 30 Dec 2017 00:50:10 +0100
From:   "Rafael J. Wysocki" <rafael@...nel.org>
To:     Tony Lindgren <tony@...mide.com>
Cc:     Jeffy Chen <jeffy.chen@...k-chips.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Linux PM <linux-pm@...r.kernel.org>,
        Shawn Lin <shawn.lin@...k-chips.com>,
        Brian Norris <briannorris@...omium.org>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Doug Anderson <dianders@...omium.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        Linux PCI <linux-pci@...r.kernel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>
Subject: Re: [RFC PATCH v12 1/5] dt-bindings: PCI: Add definition of PCIe
 WAKE# irq and PCI irq

On Fri, Dec 29, 2017 at 6:57 PM, Tony Lindgren <tony@...mide.com> wrote:
> * Jeffy Chen <jeffy.chen@...k-chips.com> [171226 02:11]:
>> We are going to handle PCIe WAKE# pin for PCI devices in the pci core,
>> so add definitions of the optional PCIe WAKE# pin for PCI devices.
>>
>> Also add an definition of the optional PCI interrupt pin for PCI
>> devices to distinguish it from the PCIe WAKE# pin.
>
>> --- a/Documentation/devicetree/bindings/pci/pci.txt
>> +++ b/Documentation/devicetree/bindings/pci/pci.txt
>> @@ -24,3 +24,13 @@ driver implementation may support the following properties:
>>     unsupported link speed, for instance, trying to do training for
>>     unsupported link speed, etc.  Must be '4' for gen4, '3' for gen3, '2'
>>     for gen2, and '1' for gen1. Any other values are invalid.
>> +
>> +PCI devices may support the following properties:
>
> This should say PCI ports instead of PCI devices.

No, it is more accurate to say "PCI devices".

Well, it actually gets somewhat confusing, because in the PCI
terminology a "PCI device" means a physical piece of hardware that can
be put into a single "slot" (think socket on a board) and may consist
up to 8 functional units called "functions" which are each represented
by a struct pci_dev.  So there may be up to 8 struct pci_dev objects
per "PCI device" (as per the standard language) and, BTW, drivers bind
to functions (via the struct pci_dev objects).

Now, WAKE# is shared by all functions within the same "PCI device"
(I'm not sure if the standard specifies that directly, but at least it
appears to be treated as an obvious physical limitation), so it may be
useful to represent the "slot" or "device" level in the DT even though
it has no struct device based representation in the kernel.

>> +- interrupts: Interrupt specifier for each name in interrupt-names.
>> +- interrupt-names:
>> +    May contain "wakeup" for PCIe WAKE# interrupt and "pci" for PCI interrupt.
>> +    The PCI devices may optionally include an 'interrupts' property that
>> +    represents the legacy PCI interrupt. And when we try to specify the PCIe
>> +    WAKE# pin, a corresponding 'interrupt-names' property is required to
>> +    distinguish them.
>> --
>> 2.11.0
>>
>>