linux-kernel - Re: [PATCH v3 1/2] dt-bindings: PCI: sprd: Document Unisoc PCIe RC host controller

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Date:   Tue, 15 Sep 2020 11:25:01 -0600
From:   Rob Herring <robh@...nel.org>
To:     Hongtao Wu <wuht06@...il.com>
Cc:     Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Orson Zhai <orsonzhai@...il.com>,
        Baolin Wang <baolin.wang7@...il.com>,
        Chunyan Zhang <zhang.lyra@...il.com>,
        linux-pci@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, Hongtao Wu <billows.wu@...soc.com>
Subject: Re: [PATCH v3 1/2] dt-bindings: PCI: sprd: Document Unisoc PCIe RC
 host controller

On Wed, Sep 09, 2020 at 05:48:31PM +0800, Hongtao Wu wrote:
> From: Hongtao Wu <billows.wu@...soc.com>
> 
> This series adds PCIe bindings for Unisoc SoCs.
> This controller is based on DesignWare PCIe IP.
> 
> Signed-off-by: Hongtao Wu <billows.wu@...soc.com>
> ---
>  .../devicetree/bindings/pci/sprd-pcie.yaml         | 101 +++++++++++++++++++++
>  1 file changed, 101 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/pci/sprd-pcie.yaml
> 
> diff --git a/Documentation/devicetree/bindings/pci/sprd-pcie.yaml b/Documentation/devicetree/bindings/pci/sprd-pcie.yaml
> new file mode 100644
> index 0000000..c52edfb
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/pci/sprd-pcie.yaml
> @@ -0,0 +1,101 @@
> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/pci/sprd-pcie.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: SoC PCIe Host Controller Device Tree Bindings
> +
> +maintainers:
> +  - Hongtao Wu <billows.wu@...soc.com>
> +
> +allOf:
> +  - $ref: /schemas/pci/pci-bus.yaml#
> +
> +properties:
> +  compatible:
> +    items:
> +      - const: sprd,pcie-rc
> +
> +  reg:
> +    minItems: 2
> +    items:
> +      - description: Controller control and status registers.
> +      - description: PCIe configuration registers.
> +
> +  reg-names:
> +    items:
> +      - const: dbi
> +      - const: config
> +
> +  ranges:
> +    maxItems: 2
> +
> +  num-lanes:
> +    maximum: 1
> +    description: Number of lanes to use for this port.
> +
> +  interrupts:
> +    minItems: 1
> +    description: Builtin MSI controller and PCIe host controller.
> +
> +  interrupt-names:
> +    items:
> +      - const: msi
> +
> +  sprd-pcie-poweron-syscons:

Doesn't match the example.

> +    minItems: 1
> +    description: Global register.
> +      The first value is the phandle to the global registers required to
> +      confige PCIe phy, clock and so on.
> +      The second value is the global register type which indicates whether it
> +      is a set/clear register or not.
> +      The third value is the time to delay after the global register is set or
> +      cleared.
> +      The fourth value is the global register address.
> +      The fifth value is the the mask value that the global register must
> +      be operate.
> +      The sixth value is the value that will be set to the global register.
> +      Note that Some Unisoc global registers have not been upstreamed.
> +      The global register and its mask can't be found in linux kernel,
> +      so we use an offset address and a number to instead them.

>From the example, it looks like you set/clear 2 bits for power on/off. 
What's the worst case you expect here? What do the 2 bits do? If they 
are for clocks, resets, or power domains, then we have bindings for 
those which should be used. This use of phandles to syscons should be 
avoided whenever possible.

If we wanted a language for specifying sequences of register accesses in 
DT, we would have defined that a long time ago.

> +
> +required:
> +  - compatible
> +  - reg
> +  - reg-names
> +  - num-lanes
> +  - ranges
> +  - interrupts
> +  - interrupt-names
> +
> +examples:
> +  - |
> +    #include <dt-bindings/interrupt-controller/arm-gic.h>
> +
> +    ipa {
> +        #address-cells = <2>;
> +        #size-cells = <2>;
> +
> +        pcie0: pcie@...00000 {
> +            compatible = "sprd,pcie-rc";
> +            reg = <0x0 0x2b100000 0x0 0x2000>,
> +                  <0x2 0x00000000 0x0 0x2000>;
> +            reg-names = "dbi", "config";
> +            #address-cells = <3>;
> +            #size-cells = <2>;
> +            device_type = "pci";
> +            ranges = <0x01000000 0x0 0x00000000 0x2 0x00002000 0x0 0x00010000>,
> +                     <0x03000000 0x0 0x10000000 0x2 0x10000000 0x1 0xefffffff>;
> +            num-lanes = <1>;
> +            interrupts = <GIC_SPI 153 IRQ_TYPE_LEVEL_HIGH>;
> +            interrupt-names = "msi";
> +
> +            sprd,pcie-poweron-syscons =
> +                <&ap_ipa_ahb_regs 0 0 0x0000 0x40 0x40>,
> +                <&ap_ipa_ahb_regs 0 0 0x0000 0x20 0x20>;
> +            sprd,pcie-poweroff-syscons =

Not documented.

> +                <&ap_ipa_ahb_regs 0 0 0x0000 0x20 0x0>,
> +                <&ap_ipa_ahb_regs 0 0 0x0000 0x40 0x0>;
> +        };
> +    };
> --
> 2.7.4
>