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

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Message-ID: <ZZos6LDk4NTfQHyU@lizhi-Precision-Tower-5810>
Date: Sat, 6 Jan 2024 23:47:36 -0500
From: Frank Li <Frank.li@....com>
To: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
Cc: 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, robh@...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 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.

> But you can make it so for all SoCs. This way, the drivers
> can also rely on it.
> 
> Now, you should get rid of the commit message about driver internals:

Not all dts already added "linux,pci-domain" yet. If required for all SOCs,
it will cause dtb check warnings.

Frank
> 
> > 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.
> > 
> 
> - Mani
> 
> > +    then:
> > +      required:
> > +        - linux,pci-domain
> > +
> >  additionalProperties: true
> >  
> >  ...
> > -- 
> > 2.34.1
> > 
> 
> -- 
> மணிவண்ணன் சதாசிவம்