Re: [PATCH] dt-bindings: nvmem: add U-Boot environment variables binding

On 2/15/22 14:49, Rafał Miłecki wrote:

From: Rafał Miłecki rafal@milecki.pl

U-Boot uses environment variables for storing device setup data on flash. That data usually needs to be accessed by a bootloader, kernel and often user-space.

This binding allows describing environment data location and its format clearly. In some/many cases it should be cleaner than hardcoding & duplicating that info in multiple places. Bootloader & kernel can share DTS and user-space can try reading it too or just have correct data exposed by a kernel.

Signed-off-by: Rafał Miłecki rafal@milecki.pl

.../devicetree/bindings/nvmem/u-boot,env.yaml | 58 +++++++++++++++++++ MAINTAINERS | 5 ++ 2 files changed, 63 insertions(+) create mode 100644 Documentation/devicetree/bindings/nvmem/u-boot,env.yaml

diff --git a/Documentation/devicetree/bindings/nvmem/u-boot,env.yaml b/Documentation/devicetree/bindings/nvmem/u-boot,env.yaml new file mode 100644 index 000000000000..a2b3a9b88eb8 --- /dev/null +++ b/Documentation/devicetree/bindings/nvmem/u-boot,env.yaml @@ -0,0 +1,58 @@ +# SPDX-License-Identifier: GPL-2.0-only OR BSD-2-Clause +%YAML 1.2 +--- +$id: http://devicetree.org/schemas/nvmem/u-boot,env.yaml# +$schema: http://devicetree.org/meta-schemas/core.yaml#

+title: U-Boot environment variables

+description: |

• U-Boot uses environment variables to store device parameters and
• configuration. They may be used for booting process, setup or keeping end user
• info.
• Data is stored on flash in a U-Boot specific format (header and NUL separated
• key-value pairs).
• This binding allows specifying data location and used format.

+maintainers:

• • Rafał Miłecki rafal@milecki.pl

+allOf:

• • $ref: nvmem.yaml#

+properties:

• compatible:
• oneOf:

•  - description: A standalone env data block
  

•    const: u-boot,env
  

•  - description: Two redundant blocks with active one flagged
  

•    const: u-boot,env-redundant-bool
  

•  - description: Two redundant blocks with active having higher counter
  

•    const: u-boot,env-redundant-count
  

I am not convinced that this is the best way how to do it. Because in u-boot implementation you would have to enable MTD partitions to get there. And the whole parsing will take a lot of time.

I think the way how I think this can be handled is.

# I don't think that discussion with Simon was finished. But for example (chosen or firmware node) chosen { u-boot { u-boot,env = <&qspi &part0>; u-boot,env-redundant = <&qspi &part1>; #or u-boot,env = <&qspi 0 40000>; u-boot,env-redundant = <&qspi 40000 40000>; #or u-boot,env = <&mmc 0 0 10000>; #device/start/size - raw mode u-boot,env = <&mmc 0 1>; # device/partition - as file to FS #etc. }; };

&qspi { flash { partitions { compatible = "fixed-partitions"; #address-cells = <1>; #size-cells = <1>;

part0: partition@0 { label = "u-boot-env"; reg = <0x0 0x40000>; };

part1: partition@40000 { label = "u-boot-env-redundant"; reg = <0x40000 0x10000>; }; }; };

Thanks, Michal