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: <ZZo4wkHf4RE2O9UN@lizhi-Precision-Tower-5810>
Date: Sun, 7 Jan 2024 00:38:10 -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 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 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.
> > 
> 
> You can safely add this property to all DTS. Nothing will break.

Yes, but it will be off topic of this patch serial.

I can submit new patches for this later. After all dts changed, then I
remove this conditional check.

This patch serial is already quite big, (17 patches).

And I don't want to involve new DTB check warning.

Frank

> 
> - Mani
> 
> > 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
> 
> -- 
> மணிவண்ணன் சதாசிவம்