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Date: Tue, 6 Feb 2024 17:47:26 -0500
From: Frank Li <Frank.li@nxp.com>
To: Rob Herring <robh@kernel.org>
Cc: Serge Semin <fancer.lancer@gmail.com>,
	Bjorn Helgaas <bhelgaas@google.com>,
	Jingoo Han <jingoohan1@gmail.com>,
	Gustavo Pimentel <gustavo.pimentel@synopsys.com>,
	Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>,
	Lorenzo Pieralisi <lpieralisi@kernel.org>,
	Krzysztof =?utf-8?Q?Wilczy=C5=84ski?= <kw@linux.com>,
	Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>,
	Conor Dooley <conor+dt@kernel.org>, imx@lists.linux.dev,
	linux-pci@vger.kernel.org, linux-kernel@vger.kernel.org,
	devicetree@vger.kernel.org
Subject: Re: [PATCH v3 5/6] dt-bindings: PCI: dwc: Add 'msg' register region
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On Mon, Feb 05, 2024 at 02:13:37PM -0500, Frank Li wrote:
> On Mon, Feb 05, 2024 at 06:30:48PM +0000, Rob Herring wrote:
> > 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@nxp.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.
> 
> Sorry, I have not understand what your means. Do you means, you want
> a "cpu-space", for example, 0x8000000 - 0x9000000 for all ATU. 
> 
> Then allocated some space to 'config', 'io', 'memory' and this 'msg'.

@rob:

    So far, I think "msg" is feasilbe solution. Or give me some little
detail direction?

Frank

> 
> Frank
> 
> > 
> > Rob