linux-kernel - Re: [PATCH v3 5/6] dt-bindings: PCI: dwc: Add 'msg' register region

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Message-ID: <20240205183048.GA3818249-robh@kernel.org>
Date: Mon, 5 Feb 2024 18:30:48 +0000
From: Rob Herring <robh@...nel.org>
To: Serge Semin <fancer.lancer@...il.com>
Cc: Frank Li <Frank.Li@....com>, Bjorn Helgaas <bhelgaas@...gle.com>,
	Jingoo Han <jingoohan1@...il.com>,
	Gustavo Pimentel <gustavo.pimentel@...opsys.com>,
	Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>,
	Lorenzo Pieralisi <lpieralisi@...nel.org>,
	Krzysztof Wilczyński <kw@...ux.com>,
	Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
	Conor Dooley <conor+dt@...nel.org>, imx@...ts.linux.dev,
	linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org,
	devicetree@...r.kernel.org
Subject: Re: [PATCH v3 5/6] dt-bindings: PCI: dwc: Add 'msg' register region

On Sat, Feb 03, 2024 at 01:44:31AM +0300, Serge Semin wrote:
> On Fri, Feb 02, 2024 at 10:11:27AM -0500, Frank Li wrote:
> > Add an outbound iATU-capable memory-region which will be used to send PCIe
> > message (such as PME_Turn_Off) to peripheral. So all platforms can use
> > common method to send out PME_Turn_Off message by using one outbound iATU.
> > 
> > Signed-off-by: Frank Li <Frank.Li@....com>
> > ---
> >  Documentation/devicetree/bindings/pci/snps,dw-pcie.yaml | 4 ++++
> >  1 file changed, 4 insertions(+)
> > 
> > diff --git a/Documentation/devicetree/bindings/pci/snps,dw-pcie.yaml b/Documentation/devicetree/bindings/pci/snps,dw-pcie.yaml
> > index 022055edbf9e6..25a5420a9ce1e 100644
> > --- a/Documentation/devicetree/bindings/pci/snps,dw-pcie.yaml
> > +++ b/Documentation/devicetree/bindings/pci/snps,dw-pcie.yaml
> > @@ -101,6 +101,10 @@ properties:
> 
> >              Outbound iATU-capable memory-region which will be used to access
> >              the peripheral PCIe devices configuration space.
> >            const: config
> > +        - description:
> > +            Outbound iATU-capable memory-region which will be used to send
> > +            PCIe message (such as PME_Turn_Off) to peripheral.
> > +          const: msg
> 
> Note there is a good chance Rob won't like this change. AFAIR he
> already expressed a concern regarding having the "config" reg-name
> describing a memory space within the outbound iATU memory which is
> normally defined by the "ranges" property. Adding a new reg-entry with
> similar semantics I guess won't receive warm welcome.

I do think it is a bit questionable. Ideally, the driver could 
just configure this on its own. However, since we don't describe all of 
the CPU address space (that's input to the iATU) already, that's not 
going to be possible. I suppose we could fix that, but then config space 
would have to be handled differently too.

Rob