linux-kernel - Re: [PATCH 1/2] dt-bindings: pci: Add Sophgo SG2044 PCIe host

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Message-ID: <2egxw3r63cbsygpwqaltp4jjlkuwoh4rkwpgv4haj4sgz5sked@vkotadyk4g6y>
Date: Sat, 22 Feb 2025 08:34:10 +0800
From: Inochi Amaoto <inochiama@...il.com>
To: Conor Dooley <conor@...nel.org>, Inochi Amaoto <inochiama@...il.com>
Cc: Lorenzo Pieralisi <lpieralisi@...nel.org>, 
	Krzysztof Wilczyński <kw@...ux.com>, Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>, 
	Rob Herring <robh@...nel.org>, Bjorn Helgaas <bhelgaas@...gle.com>, 
	Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley <conor+dt@...nel.org>, 
	Chen Wang <unicorn_wang@...look.com>, Philipp Zabel <p.zabel@...gutronix.de>, 
	Paul Walmsley <paul.walmsley@...ive.com>, Palmer Dabbelt <palmer@...belt.com>, 
	Albert Ou <aou@...s.berkeley.edu>, Niklas Cassel <cassel@...nel.org>, 
	Shashank Babu Chinta Venkata <quic_schintav@...cinc.com>, linux-pci@...r.kernel.org, devicetree@...r.kernel.org, 
	sophgo@...ts.linux.dev, linux-kernel@...r.kernel.org, linux-riscv@...ts.infradead.org, 
	Yixun Lan <dlan@...too.org>, Longbin Li <looong.bin@...il.com>
Subject: Re: [PATCH 1/2] dt-bindings: pci: Add Sophgo SG2044 PCIe host

On Fri, Feb 21, 2025 at 05:01:41PM +0000, Conor Dooley wrote:
> On Fri, Feb 21, 2025 at 09:37:55AM +0800, Inochi Amaoto wrote:
> > The pcie controller on the SG2044 is designware based with
> > custom app registers.
> > 
> > Add binding document for SG2044 PCIe host controller.
> > 
> > Signed-off-by: Inochi Amaoto <inochiama@...il.com>
> > ---
> >  .../bindings/pci/sophgo,sg2044-pcie.yaml      | 125 ++++++++++++++++++
> >  1 file changed, 125 insertions(+)
> >  create mode 100644 Documentation/devicetree/bindings/pci/sophgo,sg2044-pcie.yaml
> > 
> > diff --git a/Documentation/devicetree/bindings/pci/sophgo,sg2044-pcie.yaml b/Documentation/devicetree/bindings/pci/sophgo,sg2044-pcie.yaml
> > new file mode 100644
> > index 000000000000..040dabe905e0
> > --- /dev/null
> > +++ b/Documentation/devicetree/bindings/pci/sophgo,sg2044-pcie.yaml
> > @@ -0,0 +1,125 @@
> > +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> > +%YAML 1.2
> > +---
> > +$id: http://devicetree.org/schemas/pci/sophgo,sg2044-pcie.yaml#
> > +$schema: http://devicetree.org/meta-schemas/core.yaml#
> > +
> > +title: DesignWare based PCIe Root Complex controller on Sophgo SoCs
> > +
> > +maintainers:
> > +  - Inochi Amaoto <inochiama@...il.com>
> > +
> > +description: |+
> > +  SG2044 SoC PCIe Root Complex controller is based on the Synopsys DesignWare
> > +  PCIe IP and thus inherits all the common properties defined in
> > +  snps,dw-pcie.yaml.
> > +
> > +allOf:
> > +  - $ref: /schemas/pci/pci-host-bridge.yaml#
> > +  - $ref: /schemas/pci/snps,dw-pcie.yaml#
> > +
> > +properties:
> > +  compatible:
> > +    const: sophgo,sg2044-pcie
> > +
> > +  reg:
> > +    items:
> > +      - description: Data Bus Interface (DBI) registers
> > +      - description: iATU registers
> > +      - description: Config registers
> > +      - description: Sophgo designed configuration registers
> > +
> > +  reg-names:
> > +    items:
> > +      - const: dbi
> > +      - const: atu
> > +      - const: config
> > +      - const: app
> > +
> > +  clocks:
> > +    items:
> > +      - description: core clk
> > +
> > +  clock-names:
> > +    items:
> > +      - const: core
> > +
> > +  dma-coherent: true
> 
> Why's this here? RISC-V is dma-coherent by default, with dma-noncoherent
> used to indicate systems/devices that are not.
> 
> Cheers,
> Conor.
> 

The PCIe is dma coherent, but the SoC itself is marked as
dma-noncoherent. So I add dma-coherent to the binding. I
wonder whether dma-coherent is necessary even in this case?

Regards,
Inochi