[PATCH v2 1/3] dt-bindings: nvmem: syscon: Add syscon backed nvmem bindings

[Krzysztof Kozlowski]

On 24/05/2023 05:30, Marek Vasut wrote:
> On 5/18/23 16:26, Krzysztof Kozlowski wrote:
>> On 17/05/2023 17:25, 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.
>>>
>>> Signed-off-by: Marek Vasut <marex at denx.de>
>>> ---
>>> Cc: Alexandre Torgue <alexandre.torgue at foss.st.com>
>>> Cc: Conor Dooley <conor+dt at kernel.org>
>>> Cc: Krzysztof Kozlowski <krzysztof.kozlowski+dt at linaro.org>
>>> Cc: Marek Vasut <marex at denx.de>
>>> Cc: Maxime Coquelin <mcoquelin.stm32 at gmail.com>
>>> Cc: Rob Herring <robh+dt at kernel.org>
>>> Cc: Srinivas Kandagatla <srinivas.kandagatla at linaro.org>
>>> Cc: devicetree at vger.kernel.org
>>> Cc: kernel at dh-electronics.com
>>> Cc: linux-arm-kernel at lists.infradead.org
>>> Cc: linux-stm32 at st-md-mailman.stormreply.com
>>> ---
>>> V2: Use generic syscon supernode
>>> ---
>>>   .../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..7c1173a1a6218
>>> --- /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#"
>>
>> Usual comment: drop quotes. We removed them everywhere, so you based
>> your work on some old tree.
>>
>>> +
>>> +properties:
>>> +  compatible:
>>> +    enum:
>>> +      - nvmem-syscon
>>> +
>>> +  reg:
>>> +    maxItems: 1
>>
>> Rob's questions are not solved.
> 
> Can you reiterate this one ? I likely missed it.

You did not solve the case of more than one register. This isn't an odd
case.

> 
>> The nvmem.yaml schema expects here to
>> allow children. This should not be created per-register, but per entire
>> block of registers.
> 
> This thing works the other way around, I have a syscon register block 
> already, and I want to expose subset of it to userspace as read/write 
> accessible file to expose bootcounter available in that register (so I 
> can read it and reset it from user application).

And this makes it too limited. I would expect one device exposing
multiple blocks or registers, just like all nvmem providers are doing.


Best regards,
Krzysztof