RE: [PATCH v6 1/2] dt-bindings: PCI: xilinx-cpm: Add reset-gpios for PCIe RP PERST#

[Musham, Sai Krishna]

[AMD Official Use Only - AMD Internal Distribution Only]

Hi Krzysztof,

> -----Original Message-----
> From: Krzysztof Kozlowski <krzk@xxxxxxxxxx>
> Sent: Wednesday, March 26, 2025 1:16 PM
> To: Musham, Sai Krishna <sai.krishna.musham@xxxxxxx>
> Cc: bhelgaas@xxxxxxxxxx; lpieralisi@xxxxxxxxxx; kw@xxxxxxxxx;
> manivannan.sadhasivam@xxxxxxxxxx; robh@xxxxxxxxxx; krzk+dt@xxxxxxxxxx;
> conor+dt@xxxxxxxxxx; cassel@xxxxxxxxxx; linux-pci@xxxxxxxxxxxxxxx;
> devicetree@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; Simek, Michal
> <michal.simek@xxxxxxx>; Gogada, Bharat Kumar
> <bharat.kumar.gogada@xxxxxxx>; Havalige, Thippeswamy
> <thippeswamy.havalige@xxxxxxx>
> Subject: Re: [PATCH v6 1/2] dt-bindings: PCI: xilinx-cpm: Add reset-gpios for PCIe
> RP PERST#
>
> Caution: This message originated from an External Source. Use proper caution
> when opening attachments, clicking links, or responding.
>
>
> On Wed, Mar 26, 2025 at 07:58:10AM +0530, Sai Krishna Musham wrote:
> > Introduce `reset-gpios` property to enable GPIO-based control of the
> > PCIe RP PERST# signal, generating assert and deassert signals.
>
> I think it was removed, so this is not necessary. The property was there all the time.
Thank you for reviewing, I will update this in next patch.
>
> >
> > Traditionally, the reset was managed in hardware and enabled during
> > initialization. With this patch set, the reset will be handled by the
> > driver. Consequently, the `reset-gpios` property must be explicitly
> > provided to ensure proper functionality.
> >
> > Add CPM clock and reset control registers base (`cpm_crx`) to handle
> > PCIe IP reset along with PCIe RP PERST# to avoid Link Training errors.
>
> So does it mean it was not working before at all?
Thank you for reviewing, it was working earlier also. Currently boards are designed to handle
PERST# and IP reset from software driver, and IP reset is being removed from design.
I will update the commit message in next patch.
>
> >
> > Signed-off-by: Sai Krishna Musham <sai.krishna.musham@xxxxxxx>
> > ---
> > Changes for v6:
> > - Resolve ABI break.
> > - Update commit message.
> >
> > Changes for v5:
> > - Remove `reset-gpios` property from required as it is already present
> >   in pci-bus-common.yaml
> > - Update commit message
> >
> > Changes for v4:
> > - Add CPM clock and reset control registers base to handle PCIe IP
> >   reset.
> > - Update commit message.
> >
> > Changes for v3:
> > - None
> >
> > Changes for v2:
> > - Add define from include/dt-bindings/gpio/gpio.h for PERST# polarity
> > - Update commit message
> > ---
> >  .../bindings/pci/xilinx-versal-cpm.yaml       | 72 ++++++++++++++-----
> >  1 file changed, 55 insertions(+), 17 deletions(-)
> >
> > diff --git
> > a/Documentation/devicetree/bindings/pci/xilinx-versal-cpm.yaml
> > b/Documentation/devicetree/bindings/pci/xilinx-versal-cpm.yaml
> > index d674a24c8ccc..26e9cea41889 100644
> > --- a/Documentation/devicetree/bindings/pci/xilinx-versal-cpm.yaml
> > +++ b/Documentation/devicetree/bindings/pci/xilinx-versal-cpm.yaml
> > @@ -9,9 +9,6 @@ title: CPM Host Controller device tree for Xilinx
> > Versal SoCs
> >  maintainers:
> >    - Bharat Kumar Gogada <bharat.kumar.gogada@xxxxxxx>
> >
> > -allOf:
> > -  - $ref: /schemas/pci/pci-host-bridge.yaml#
> > -
> >  properties:
> >    compatible:
> >      enum:
> > @@ -21,18 +18,12 @@ properties:
> >        - xlnx,versal-cpm5nc-host
> >
> >    reg:
> > -    items:
> > -      - description: CPM system level control and status registers.
> > -      - description: Configuration space region and bridge registers.
> > -      - description: CPM5 control and status registers.
> > -    minItems: 2
> > +    minItems: 3
>
> That's an ABI break.
Thanks for reviewing, I will update minItems to 2, so it will not be an ABI break.
>
> > +    maxItems: 4
> >
> >    reg-names:
> > -    items:
> > -      - const: cpm_slcr
> > -      - const: cfg
> > -      - const: cpm_csr
> > -    minItems: 2
> > +    minItems: 3
> > +    maxItems: 4
> >
> >    interrupts:
> >      maxItems: 1
> > @@ -72,10 +63,53 @@ required:
> >    - msi-map
> >    - interrupt-controller
> >
> > +allOf:
> > +  - $ref: /schemas/pci/pci-host-bridge.yaml#
> > +  - if:
> > +      properties:
> > +        compatible:
> > +          contains:
> > +            enum:
> > +              - xlnx,versal-cpm-host-1.00
> > +    then:
> > +      properties:
> > +        reg:
> > +          items:
> > +            - description: CPM system level control and status registers.
> > +            - description: Configuration space region and bridge registers.
> > +            - description: CPM clock and reset control registers.
>
> Before two items, now min 3, so another ABI break. Missing minItems.
Thanks for reviewing, I will update minItems to 2, so it will not be an ABI break.
>
> > +        reg-names:
> > +          items:
> > +            - const: cpm_slcr
> > +            - const: cfg
> > +            - const: cpm_crx
>
> Same
Thanks for reviewing, I will update minItems to 2, so it will not be an ABI break.
>
> > +  - if:
> > +      properties:
> > +        compatible:
> > +          contains:
> > +            enum:
> > +              - xlnx,versal-cpm5-host
> > +              - xlnx,versal-cpm5-host1
> > +    then:
> > +      properties:
> > +        reg:
> > +          items:
> > +            - description: CPM system level control and status registers.
> > +            - description: Configuration space region and bridge registers.
> > +            - description: CPM5 control and status registers.
> > +            - description: CPM clock and reset control registers.
>
> This makes no sense, you still add the entry in the middle. This patch fixed nothing
> from issues previously pointed out.
>
> It's the third or fourth try and you keep repeating the same mistake, which means
> you do not understand the problem. The problem is: you cannot change the order. If
> you change it, it's an ABI break and nothing in commit msg explained that.
Thanks for reviewing, I will update minItems to 3, so it will not be an ABI break.
And currently in this patch I have a cpm_crx property at the end.
This is the description for cpm_crx.
            - description: CPM clock and reset control registers.

Below is the updated version of this patch. Please let me know if you have any further comments.
       - xlnx,versal-cpm5nc-host

   reg:
-    minItems: 3
+    minItems: 2
     maxItems: 4

   reg-names:
-    minItems: 3
+    minItems: 2
     maxItems: 4

   interrupts:
@@ -78,11 +78,13 @@ allOf:
             - description: CPM system level control and status registers.
             - description: Configuration space region and bridge registers.
             - description: CPM clock and reset control registers.
+          minItems: 2
         reg-names:
           items:
             - const: cpm_slcr
             - const: cfg
             - const: cpm_crx
+          minItems: 2
   - if:
       properties:
         compatible:
@@ -98,12 +100,14 @@ allOf:
             - description: Configuration space region and bridge registers.
             - description: CPM5 control and status registers.
             - description: CPM clock and reset control registers.
+          minItems: 3
         reg-names:
           items:
             - const: cpm_slcr
             - const: cfg
             - const: cpm_csr
             - const: cpm_crx
+          minItems: 3

 unevaluatedProperties: false
>
> Best regards,
> Krzysztof

Regards,
Sai Krishna