[PATCH v9 2/3] dt-bindings: PCI: pci-imx6: Add external reference clock input

[Hongxing Zhu]

> -----Original Message-----
> From: Krzysztof Kozlowski <krzk at kernel.org>
> Sent: 2025年11月3日 0:05
> To: Hongxing Zhu <hongxing.zhu at nxp.com>
> Cc: robh at kernel.org; krzk+dt at kernel.org; conor+dt at kernel.org;
> bhelgaas at google.com; Frank Li <frank.li at nxp.com>; l.stach at pengutronix.de;
> lpieralisi at kernel.org; kwilczynski at kernel.org; mani at kernel.org;
> shawnguo at kernel.org; s.hauer at pengutronix.de; kernel at pengutronix.de;
> festevam at gmail.com; linux-pci at vger.kernel.org;
> linux-arm-kernel at lists.infradead.org; devicetree at vger.kernel.org;
> imx at lists.linux.dev; linux-kernel at vger.kernel.org
> Subject: Re: [PATCH v9 2/3] dt-bindings: PCI: pci-imx6: Add external reference
> clock input
> 
> On Fri, Oct 31, 2025 at 11:19:06AM +0800, Richard Zhu wrote:
> > i.MX95 PCIes have two reference clock inputs: one from internal PLL,
> > the other from off chip crystal oscillator. The "extref" clock refers
> > to a reference clock from an external crystal oscillator.
> >
> > Add external reference clock input for i.MX95 PCIes.
> >
> > Signed-off-by: Richard Zhu <hongxing.zhu at nxp.com>
> > Reviewed-by: Frank Li <Frank.Li at nxp.com>
> > ---
> >  Documentation/devicetree/bindings/pci/fsl,imx6q-pcie.yaml | 7 +++++--
> >  1 file changed, 5 insertions(+), 2 deletions(-)
> >
> > diff --git a/Documentation/devicetree/bindings/pci/fsl,imx6q-pcie.yaml
> > b/Documentation/devicetree/bindings/pci/fsl,imx6q-pcie.yaml
> > index ca5f2970f217c..703c776d28e6f 100644
> > --- a/Documentation/devicetree/bindings/pci/fsl,imx6q-pcie.yaml
> > +++ b/Documentation/devicetree/bindings/pci/fsl,imx6q-pcie.yaml
> > @@ -44,7 +44,7 @@ properties:
> >
> >    clock-names:
> >      minItems: 3
> > -    maxItems: 5
> > +    maxItems: 6
> >
> >    interrupts:
> >      minItems: 1
> > @@ -212,14 +212,17 @@ allOf:
> >      then:
> >        properties:
> >          clocks:
> > -          maxItems: 5
> > +          minItems: 4
> > +          maxItems: 6
> >          clock-names:
> > +          minItems: 4
> >            items:
> >              - const: pcie
> >              - const: pcie_bus
> >              - const: pcie_phy
> >              - const: pcie_aux
> >              - const: ref
> 
> This was required last time. Nothing in commit msg explained changing that.
> 
> > +            - const: extref  # Optional
> 
> Drop the comment, do not repeat the schema. And why only this is marked
> as optional if 'ref' is optional as well now.

Hi Krzysztof:
Thanks for your comments, I know what's the problem in this patch.
Firstly, the minItem and maxItem of i.MX95 PCIe clocks should be 5 and 6.
Because that the "ref" clock is not an optional clock for i.MX95 PCIes.

How about to update the commits as follows?
"
i.MX95 PCIes have two reference clock inputs: one from internal PLL. It's
wired inside chip and present as "ref" clock. It's not an optional clock.
The other from off chip crystal oscillator. The "extref" clock refers to a
reference clock from an external crystal oscillator through the CLKIN_N/P pair
PADs. It is an optional clock, relied on the board design.

Add additional optional external reference clock input for i.MX95 PCIes.
"
Thanks.

Best Regards
Richard Zhu

> 
> It is v9, can you please really think thoroughly what you are sending, so
> obvious issues won't be there?
> 
> Best regards,
> Krzysztof