Re: [PATCH 1/4] dt-bindings: reset: add generic bit reset controller

From: Philipp Zabel
Date: Thu Feb 13 2025 - 05:10:44 EST


On Do, 2025-02-13 at 10:08 +0800, Inochi Amaoto wrote:
> Some SoCs from Aspeed, Allwinner, Sophgo and Synopsys have
> a simple reset controller by toggling bit. It is a hard time
> for each device to add its own compatible to the driver.
> Since this device share a common design, it is possible to
> add a common device to reduce these unnecessary change.
>
> Add common binding for these kind generic reset controller.
>
> Signed-off-by: Inochi Amaoto <inochiama@xxxxxxxxx>
> ---
> .../bindings/reset/reset-simple.yaml | 42 +++++++++++++++++++
> 1 file changed, 42 insertions(+)
> create mode 100644 Documentation/devicetree/bindings/reset/reset-simple.yaml
>
> diff --git a/Documentation/devicetree/bindings/reset/reset-simple.yaml b/Documentation/devicetree/bindings/reset/reset-simple.yaml
> new file mode 100644
> index 000000000000..77584e23e8e8
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/reset/reset-simple.yaml
> @@ -0,0 +1,42 @@
> +# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/reset/reset-simple.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: Generic BIT Reset Controller
> +
> +maintainers:
> + - Inochi Amaoto <inochiama@xxxxxxxxx>
> +
> +description:
> + Some reset controller devices uses a simple method to perform
> + assert/deassert by toggling bit. Some SoCs from Aspeed, Allwinner,
> + Sophgo and Synopsys have this kind of reset controller instances.

I think some properties should be documented that make reset
controllers "simple" according to this binding.

For example, right now, the reset-simple driver assumes the following:

- There is a single, contiguous range of 32-bit registers.
- All bits in each register directly control a reset line.
- There are no self-deasserting resets.
- There are no timing requirements.
- The bits are exclusively resets, nothing else.
- All bits behave the same, so all reset bits are either
active-high or all are active-low.
- The bits can be read back, but the read status may
be active-low independently from the writes.

> +properties:
> + compatible:
> + enum:
> + - reset-simple-high
> + - reset-simple-low

I wonder if it would be better to have a single

compatible:
const: reset-simple

and a boolean property, e.g.

active-low:
type: boolean

like in leds/common.yaml. Also it should be documented clearly what
this means for reads and writes.

> + reg:
> + maxItems: 1
> +
> + "#reset-cells":
> + const: 1
> +
> +required:
> + - compatible
> + - reg
> + - "#reset-cells"
> +
> +additionalProperties: false
> +
> +examples:
> + - |
> + reset-controller@1000000 {
> + compatible = "reset-simple-high";

The example should probably include a SoC specific compatible?

regards
Philipp