linux-kernel - Re: [PATCH v7 04/16] dt-bindings: imx6q-pcie: Add linux,pci-domain as required for iMX8MQ

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Date: Mon, 8 Jan 2024 20:49:34 -0700
From: Rob Herring <robh@...nel.org>
To: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
Cc: Frank Li <Frank.li@....com>, krzysztof.kozlowski@...aro.org, bhelgaas@...gle.com, conor+dt@...nel.org, devicetree@...r.kernel.org, festevam@...il.com, helgaas@...nel.org, hongxing.zhu@....com, imx@...ts.linux.dev, kernel@...gutronix.de, krzysztof.kozlowski+dt@...aro.org, kw@...ux.com, l.stach@...gutronix.de, linux-arm-kernel@...ts.infradead.org, linux-imx@....com, linux-kernel@...r.kernel.org, linux-pci@...r.kernel.org, lpieralisi@...nel.org, s.hauer@...gutronix.de, shawnguo@...nel.org
Subject: Re: [PATCH v7 04/16] dt-bindings: imx6q-pcie: Add linux,pci-domain
 as required for iMX8MQ

On Sun, Jan 07, 2024 at 11:59:11AM +0530, Manivannan Sadhasivam wrote:
> On Sun, Jan 07, 2024 at 12:38:10AM -0500, Frank Li wrote:
> > On Sun, Jan 07, 2024 at 10:49:17AM +0530, Manivannan Sadhasivam wrote:
> > > On Sat, Jan 06, 2024 at 11:47:36PM -0500, Frank Li wrote:
> > > > On Sun, Jan 07, 2024 at 08:45:06AM +0530, Manivannan Sadhasivam wrote:
> > > > > On Wed, Dec 27, 2023 at 01:27:15PM -0500, Frank Li wrote:
> > > > > > iMX8MQ have two pci controllers. Adds "linux,pci-domain" as required
> > > > > > proptery for iMX8MQ to indicate pci controller index.
> > > > > > 
> > > > > 
> > > > > property
> > > > > 
> > > > > > This adjustment paves the way for eliminating the hardcoded check on the
> > > > > > base register for acquiring the controller_id.
> > > > > > 
> > > > > > 	...
> > > > > > 	if (dbi_base->start == IMX8MQ_PCIE2_BASE_ADDR)
> > > > > > 		imx6_pcie->controller_id = 1;
> > > > > > 	...
> > > > > > 
> > > > > > The controller_id is crucial and utilized for certain register bit
> > > > > > positions. It must align precisely with the controller index in the SoC.
> > > > > > An auto-incremented ID don't fit this case. The DTS or fuse configurations
> > > > > > may deactivate specific PCI controllers.
> > > > > > 
> > > > > 
> > > > > You cannot change the binding for the sake of driver. But you can make this
> > > > > change in other way. See below...
> > > > > 
> > > > > > Signed-off-by: Frank Li <Frank.Li@....com>
> > > > > > ---
> > > > > > 
> > > > > > Notes:
> > > > > >     Change from v5 to v6
> > > > > >     - rework commit message to explain why need required and why auto increase
> > > > > >     id not work
> > > > > >     
> > > > > >     Change from v4 to v5
> > > > > >     - new patch at v5
> > > > > > 
> > > > > >  .../bindings/pci/fsl,imx6q-pcie-common.yaml           | 11 +++++++++++
> > > > > >  1 file changed, 11 insertions(+)
> > > > > > 
> > > > > > diff --git a/Documentation/devicetree/bindings/pci/fsl,imx6q-pcie-common.yaml b/Documentation/devicetree/bindings/pci/fsl,imx6q-pcie-common.yaml
> > > > > > index d91b639ae7ae7..8f39b4e6e8491 100644
> > > > > > --- a/Documentation/devicetree/bindings/pci/fsl,imx6q-pcie-common.yaml
> > > > > > +++ b/Documentation/devicetree/bindings/pci/fsl,imx6q-pcie-common.yaml
> > > > > > @@ -265,6 +265,17 @@ allOf:
> > > > > >              - const: apps
> > > > > >              - const: turnoff
> > > > > >  
> > > > > > +  - if:
> > > > > > +      properties:
> > > > > > +        compatible:
> > > > > > +          contains:
> > > > > > +            enum:
> > > > > > +              - fsl,imx8mq-pcie
> > > > > > +              - fsl,imx8mq-pcie-ep
> > > > > 
> > > > > "linux,pci-domain" is a generic property. So you cannot make it required only
> > > > > for certain SoCs. 
> > > > 
> > > > Sorry, why not? there are many generic property.
> > > > 
> > > 
> > > It doesn't make sense to make it required only for specific SoCs since it is not
> > > specific to any SoC. You can make it required for all.
> > 
> > More than 2 controller need require "linux,pci-domain".
> >
> 
> But this property is applicable to single controller also.

Not really.

I don't understand the issue. Some SoCs have a dependency on the 
numbering and need the property. Others don't. They just want 
(but don't need) consistent numbering. 

Rob