[PATCH] dt-bindings: nvmem: add U-Boot environment variables binding
Michal Simek
michal.simek at xilinx.com
Wed Feb 16 15:28:06 CET 2022
On 2/16/22 13:59, Rafał Miłecki wrote:
> On 15.02.2022 15:57, Sean Anderson wrote:
>> On 2/15/22 9:02 AM, Michal Simek wrote:
>>>
>>>
>>> On 2/15/22 14:49, Rafał Miłecki wrote:
>>>> From: Rafał Miłecki <rafal at 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 at 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 at 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>;
>>
>> What about when the environment is on top of UBI?
>
> We can always add support for binding UBI volumes in DT. Somethig
> more-or-less like:
>
> partitions {
> compatible = "fixed-partitions";
> #address-cells = <1>;
> #size-cells = <1>;
>
> partition at 0 {
> compatible = "ubi";
> label = "ubi";
> reg = <0x0 0x1000000>;
>
> env0: partition-0 {
> volume-name = "env";
> };
>
> env1: partition-1 {
> volume-id = <10>;
> };
> };
> };
If this is something ack by Rob I have no problem with it. But it has to go to
schema.
M
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