linux-kernel - Re: [PATCH v5 2/4] dt-bindings: aspeed: Add UART routing controller

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Date:   Thu, 16 Sep 2021 15:18:51 -0500
From:   Rob Herring <robh@...nel.org>
To:     Chia-Wei Wang <chiawei_wang@...eedtech.com>
Cc:     joel@....id.au, andrew@...id.au,
        linux-arm-kernel@...ts.infradead.org,
        linux-aspeed@...ts.ozlabs.org, linux-kernel@...r.kernel.org,
        devicetree@...r.kernel.org, openbmc@...ts.ozlabs.org,
        osk@...gle.com, yulei.sh@...edance.com
Subject: Re: [PATCH v5 2/4] dt-bindings: aspeed: Add UART routing controller

On Thu, Sep 16, 2021 at 05:25:13PM +0800, Chia-Wei Wang wrote:
> Add dt-bindings for Aspeed UART routing controller.
> 
> Signed-off-by: Oskar Senft <osk@...gle.com>
> Signed-off-by: Chia-Wei Wang <chiawei_wang@...eedtech.com>
> ---
>  .../devicetree/bindings/mfd/aspeed-lpc.yaml   |  4 ++
>  .../bindings/soc/aspeed/uart-routing.yaml     | 70 +++++++++++++++++++
>  2 files changed, 74 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/soc/aspeed/uart-routing.yaml
> 
> diff --git a/Documentation/devicetree/bindings/mfd/aspeed-lpc.yaml b/Documentation/devicetree/bindings/mfd/aspeed-lpc.yaml
> index 54f080df5e2f..697331d840a0 100644
> --- a/Documentation/devicetree/bindings/mfd/aspeed-lpc.yaml
> +++ b/Documentation/devicetree/bindings/mfd/aspeed-lpc.yaml
> @@ -142,6 +142,10 @@ patternProperties:
>        - interrupts
>        - snoop-ports
>  
> +  "^uart-routing@[0-9a-f]+$":
> +    $ref: /schemas/soc/aspeed/uart-routing.yaml#
> +    description: The UART routing control under LPC register space
> +
>  required:
>    - compatible
>    - reg
> diff --git a/Documentation/devicetree/bindings/soc/aspeed/uart-routing.yaml b/Documentation/devicetree/bindings/soc/aspeed/uart-routing.yaml
> new file mode 100644
> index 000000000000..534b2a9340ce
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/soc/aspeed/uart-routing.yaml
> @@ -0,0 +1,70 @@
> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> +# # Copyright (c) 2018 Google LLC
> +# # Copyright (c) 2021 Aspeed Technology Inc.
> +%YAML 1.2
> +---
> +$id: "http://devicetree.org/schemas/soc/aspeed/uart-routing.yaml#"
> +$schema: "http://devicetree.org/meta-schemas/core.yaml#"
> +
> +title: Aspeed UART Routing Controller
> +
> +maintainers:
> +  - Oskar Senft <osk@...gle.com>
> +  - Chia-Wei Wang <chiawei_wang@...eedtech.com>
> +
> +description:
> +  The Aspeed UART routing control allow to dynamically route the inputs for
> +  the built-in UARTS and physical serial I/O ports.
> +
> +  This allows, for example, to connect the output of UART to another UART.
> +  This can be used to enable Host <-> BMC communication via UARTs, e.g. to
> +  allow access to the Host's serial console.
> +
> +  This driver is for the BMC side. The sysfs files allow the BMC userspace
> +  which owns the system configuration policy, to configure how UARTs and
> +  physical serial I/O ports are routed.
> +
> +  Two types of files, uart* and io*, are presented in sysfs. The uart*
> +  configures the input signal of a UART controller whereas io* configures
> +  that of a physical serial port.
> +
> +  When read, each file shows the list of available options with currently
> +  selected option marked by brackets "[]". The list of available options
> +  depends on the selected file.
> +
> +  e.g.
> +  cat /sys/bus/platform/drivers/aspeed-uart-routing/*.uart_routing/uart1
> +  [io1] io2 io3 io4 uart2 uart3 uart4 io6
> +
> +  In this case, UART1 gets its input from IO1 (physical serial port 1).

This is about documenting the hardware, not an OS driver.

sysfs files have their own documentation.

> +
> +properties:
> +  compatible:
> +    items:
> +      - enum:
> +          - aspeed,ast2400-uart-routing
> +          - aspeed,ast2500-uart-routing
> +          - aspeed,ast2600-uart-routing
> +  reg:
> +    maxItems: 1
> +
> +required:
> +  - compatible
> +
> +additionalProperties: false
> +
> +examples:
> +  - |
> +    lpc: lpc@...89000 {
> +        compatible = "aspeed,ast2600-lpc-v2", "simple-mfd", "syscon";
> +        reg = <0x1e789000 0x1000>;
> +
> +        #address-cells = <1>;
> +        #size-cells = <1>;
> +        ranges = <0x0 0x1e789000 0x1000>;
> +
> +        uart_routing: uart-routing@98 {
> +            compatible = "aspeed,ast2600-uart-routing";
> +            reg = <0x98 0x8>;
> +        };
> +    };
> -- 
> 2.17.1
> 
>