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

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Message-ID: <20250224-enable-progress-e3a47fdb625c@spud>
Date: Mon, 24 Feb 2025 18:54:51 +0000
From: Conor Dooley <conor@...nel.org>
To: 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 Sat, Feb 22, 2025 at 08:34:10AM +0800, Inochi Amaoto wrote:
> 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.
> 
> The PCIe is dma coherent, but the SoC itself is marked as
> dma-noncoherent.

By "the SoC itself", do you mean that the bus that this device is on is
marked as dma-noncoherent? IMO, that should not be done if there are
devices on it that are coherent.

> So I add dma-coherent to the binding. I
> wonder whether dma-coherent is necessary even in this case?


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