linux-kernel - Re: [RFC PATCH v10 1/7] dt-bindings: PCI: Add definition of PCIe WAKE# irq and PCI irq

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Message-ID: <20171027204513.GA105121@google.com>
Date:   Fri, 27 Oct 2017 13:45:17 -0700
From:   Brian Norris <briannorris@...omium.org>
To:     Jeffy Chen <jeffy.chen@...k-chips.com>
Cc:     linux-kernel@...r.kernel.org, bhelgaas@...gle.com,
        linux-pm@...r.kernel.org, tony@...mide.com,
        shawn.lin@...k-chips.com, rjw@...ysocki.net, dianders@...omium.org,
        devicetree@...r.kernel.org, linux-pci@...r.kernel.org,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>
Subject: Re: [RFC PATCH v10 1/7] dt-bindings: PCI: Add definition of PCIe
 WAKE# irq and PCI irq

Hi,

On Fri, Oct 27, 2017 at 03:26:06PM +0800, Jeffy Chen wrote:
> We are going to handle PCIe WAKE# pin for PCI bus bridges and PCI
> devices in the pci core, so add definitions of the optional PCIe
> WAKE# pin for PCI bus bridges and PCI devices.
> 
> Also add an definition of the optional PCI interrupt pin for PCI
> devices to distinguish it from the PCIe WAKE# pin.
> 
> Signed-off-by: Jeffy Chen <jeffy.chen@...k-chips.com>
> ---
> 
> Changes in v10: None
> Changes in v9:
> Add section for PCI devices and rewrite the commit message.
> 
> Changes in v8:
> Add optional "pci", and rewrite commit message.
> 
> Changes in v7: None
> Changes in v6: None
> Changes in v5:
> Move to pci.txt
> 
> Changes in v3: None
> Changes in v2: None
> 
>  Documentation/devicetree/bindings/pci/pci.txt | 8 ++++++++
>  1 file changed, 8 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/pci/pci.txt b/Documentation/devicetree/bindings/pci/pci.txt
> index c77981c5dd18..d4406d4e15ad 100644
> --- a/Documentation/devicetree/bindings/pci/pci.txt
> +++ b/Documentation/devicetree/bindings/pci/pci.txt
> @@ -24,3 +24,11 @@ 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.
> +- interrupts: Interrupt specifier for each name in interrupt-names.
> +- interrupt-names: May contains "wakeup" for PCIe WAKE# interrupt.

s/contains/contain/

> +
> +PCI devices have standardized Device Tree bindings:

This line is a little unclear, especially since there *is* an old
documented standard, yet the following text is actually introducing new,
non-standard additions.

> +
> +- interrupts: Interrupt specifier for each name in interrupt-names.
> +- interrupt-names: May contains "wakeup" for PCIe WAKE# interrupt and "pci" for

s/contains/contain/

> +  PCI interrupt.

IMO, since you're trying to augment a standardized binding, you need to
be a lot clearer here. I expect you should mention the existing standard
(that devices may optionally include an 'interrupts' property that
represents the legacy PCI interrupt) and how you're augmenting it (that
additional interrupts can be supported optionally, but they require a
corresponding 'interrupt-names' property).

Also, is this binding only applying either to a host bridge or to
devices? No intermediate bridges or ports? It seems so, but I wanted to
be clear. (And it probably could be extended if needed. Notably, ACPI
has a tree-walk implementation, so if the device itself doesn't have
a wakeup config, it can look into any of its parents.)

Once you fix up the documentation...I suppose this looks like a sane
idea. But I'd like 2nd opinions on this.

Brian