[PATCH 1/3] [RFC] dt-bindings: nvmem: syscon: Add syscon backed nvmem bindings
Rob Herring
robh at kernel.org
Fri Oct 28 14:28:38 PDT 2022
On Fri, Oct 28, 2022 at 12:50:18AM +0200, Marek Vasut wrote:
> Add trivial bindings for driver which permits exposing syscon backed
> register to userspace. This is useful e.g. to expose U-Boot boot
> counter on various platforms where the boot counter is stored in
> random volatile register, like STM32MP15xx TAMP_BKPxR register.
Generic bindings always start trivial until they get appended one
property at a time...
What happens when you have more than 1 field and/or more than 1
register?
> Signed-off-by: Marek Vasut <marex at denx.de>
> ---
> Cc: Alexandre Torgue <alexandre.torgue at foss.st.com>
> Cc: Rafał Miłecki <rafal at milecki.pl>
> Cc: Rob Herring <robh+dt at kernel.org>
> Cc: Srinivas Kandagatla <srinivas.kandagatla at linaro.org>
> Cc: devicetree at vger.kernel.org
> Cc: linux-stm32 at st-md-mailman.stormreply.com
> To: linux-arm-kernel at lists.infradead.org
> ---
> .../bindings/nvmem/nvmem-syscon.yaml | 39 +++++++++++++++++++
> 1 file changed, 39 insertions(+)
> create mode 100644 Documentation/devicetree/bindings/nvmem/nvmem-syscon.yaml
>
> diff --git a/Documentation/devicetree/bindings/nvmem/nvmem-syscon.yaml b/Documentation/devicetree/bindings/nvmem/nvmem-syscon.yaml
> new file mode 100644
> index 0000000000000..3035a0b2cd24a
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/nvmem/nvmem-syscon.yaml
> @@ -0,0 +1,39 @@
> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/nvmem/nvmem-syscon.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: Generic syscon backed nvmem
> +
> +maintainers:
> + - Marek Vasut <marex at denx.de>
> +
> +allOf:
> + - $ref: "nvmem.yaml#"
> +
> +properties:
> + compatible:
> + enum:
> + - nvmem-syscon
> +
> + reg:
> + maxItems: 1
> +
> +required:
> + - compatible
> + - reg
> +
> +additionalProperties: false
> +
> +examples:
> + - |
> + tamp at 5c00a000 {
> + compatible = "st,stm32-tamp", "syscon", "simple-mfd";
This is very common, but personally I think "syscon" and "simple-mfd"
should be mutually exclusive. "simple-mfd" is saying the children have
no dependency on the parent, yet the child nodes need a regmap from the
parent. Sounds like a dependency.
> + reg = <0x5c00a000 0x400>;
> +
> + nvmem-syscon {
> + compatible = "nvmem-syscon";
> + reg = <0x14c 0x4>;
How does one identify this is the bootloader's boot count? How does the
bootloader know it can write to this?
> + };
> + };
> --
> 2.35.1
>
>
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