diff mbox series

[v2,4/8] dt-bindings: power: reset: add bindings for NVMEM hardware storing PSCR Data

Message ID 20240124122204.730370-5-o.rempel@pengutronix.de (mailing list archive)
State Handled Elsewhere, archived
Headers show
Series Introduction of PSCR Framework and Related Components | expand

Commit Message

Oleksij Rempel Jan. 24, 2024, 12:22 p.m. UTC
Add device tree bindings that describe hardware implementations of
Non-Volatile Memory (NVMEM) used for storing Power State Change Reasons
(PSCR).

Signed-off-by: Oleksij Rempel <o.rempel@pengutronix.de>
---
 .../bindings/power/reset/pscrr-nvmem.yaml     | 53 +++++++++++++++++++
 1 file changed, 53 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/power/reset/pscrr-nvmem.yaml

Comments

Krzysztof Kozlowski Jan. 25, 2024, 10:57 a.m. UTC | #1
On 24/01/2024 13:22, Oleksij Rempel wrote:
> Add device tree bindings that describe hardware implementations of
> Non-Volatile Memory (NVMEM) used for storing Power State Change Reasons
> (PSCR).

A nit, subject: drop second/last, redundant "bindings for". The
"dt-bindings" prefix is already stating that these are bindings.
See also:
https://elixir.bootlin.com/linux/v6.7-rc8/source/Documentation/devicetree/bindings/submitting-patches.rst#L18

> 
> Signed-off-by: Oleksij Rempel <o.rempel@pengutronix.de>
> ---
>  .../bindings/power/reset/pscrr-nvmem.yaml     | 53 +++++++++++++++++++
>  1 file changed, 53 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/power/reset/pscrr-nvmem.yaml
> 
> diff --git a/Documentation/devicetree/bindings/power/reset/pscrr-nvmem.yaml b/Documentation/devicetree/bindings/power/reset/pscrr-nvmem.yaml
> new file mode 100644
> index 000000000000..779920dea283
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/power/reset/pscrr-nvmem.yaml
> @@ -0,0 +1,53 @@
> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/power/reset/pscrr-nvmem.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: Generic NVMEM Power State Change Reason Recorder
> +
> +maintainers:
> +  - Oleksij Rempel <o.rempel@pengutronix.de>
> +
> +description: This binding describes the Non-Volatile Memory (NVMEM) hardware

Same comment and also: describe the hardware, not the binding. s/This
binding describes/something useful/

> +  that stores Power State Change Reasons (PSCR).
> +
> +allOf:
> +  - $ref: pscrr.yaml#
> +
> +properties:
> +  compatible:
> +    const: pscrr-nvmem
> +

So that's a driver :/. Maybe Rob will like it, but it's a no from me.
Please come up with something really suiting DEVICES, not DRIVERS.

> +  nvmem-cells:
> +    description: |

Do not need '|' unless you need to preserve formatting.

> +      A phandle pointing to the nvmem-cells node where the power state change
> +      reasons are stored.
> +    maxItems: 1
> +


Best regards,
Krzysztof
Oleksij Rempel Jan. 25, 2024, 5:11 p.m. UTC | #2
On Thu, Jan 25, 2024 at 11:57:18AM +0100, Krzysztof Kozlowski wrote:
> On 24/01/2024 13:22, Oleksij Rempel wrote:
> > Add device tree bindings that describe hardware implementations of
> > Non-Volatile Memory (NVMEM) used for storing Power State Change Reasons
> > (PSCR).
> > +  that stores Power State Change Reasons (PSCR).
> > +
> > +allOf:
> > +  - $ref: pscrr.yaml#
> > +
> > +properties:
> > +  compatible:
> > +    const: pscrr-nvmem
> > +
> 
> So that's a driver :/. Maybe Rob will like it, but it's a no from me.
> Please come up with something really suiting DEVICES, not DRIVERS.

If I understand your distinction between 'DEVICES' and 'DRIVERS'
correctly, 'DEVICES' in the device tree context are meant to represent
physical hardware components, while 'DRIVERS' refer to software
abstractions of these components. However, there are numerous device
tree instances, like software-based implementations for SPI, I2C, or
GPIO, which could also be interpreted as 'DRIVERS' in the context of
your email. Similarly, the binding for PSCRR represents functionality not
fully implemented in hardware but supported by the hardware component of
NVMEM, akin to how ramoops or other functionalities are represented.

If I'm misunderstanding your distinction between 'DEVICES' and
'DRIVERS', please clarify with an example of how a proper binding should
be implemented for a case like this.

Regards,
Oleksij
Krzysztof Kozlowski Jan. 26, 2024, 9:03 a.m. UTC | #3
On 25/01/2024 18:11, Oleksij Rempel wrote:
> On Thu, Jan 25, 2024 at 11:57:18AM +0100, Krzysztof Kozlowski wrote:
>> On 24/01/2024 13:22, Oleksij Rempel wrote:
>>> Add device tree bindings that describe hardware implementations of
>>> Non-Volatile Memory (NVMEM) used for storing Power State Change Reasons
>>> (PSCR).
>>> +  that stores Power State Change Reasons (PSCR).
>>> +
>>> +allOf:
>>> +  - $ref: pscrr.yaml#
>>> +
>>> +properties:
>>> +  compatible:
>>> +    const: pscrr-nvmem
>>> +
>>
>> So that's a driver :/. Maybe Rob will like it, but it's a no from me.
>> Please come up with something really suiting DEVICES, not DRIVERS.
> 
> If I understand your distinction between 'DEVICES' and 'DRIVERS'
> correctly, 'DEVICES' in the device tree context are meant to represent
> physical hardware components, while 'DRIVERS' refer to software

Yes.

> abstractions of these components. However, there are numerous device
> tree instances, like software-based implementations for SPI, I2C, or
> GPIO, which could also be interpreted as 'DRIVERS' in the context of

True. Yet they are still for physical interfaces. There is no DTS having
some virtual I2C for a board which does not have I2C.

> your email. Similarly, the binding for PSCRR represents functionality not
> fully implemented in hardware but supported by the hardware component of
> NVMEM, akin to how ramoops or other functionalities are represented.

You don't need a binding for your case. Instantiate it whatever you wish
- modprobe for example - and configure through approved kernel
interfaces - sysfs for example.

Best regards,
Krzysztof
Oleksij Rempel Jan. 26, 2024, 4:51 p.m. UTC | #4
On Fri, Jan 26, 2024 at 10:03:51AM +0100, Krzysztof Kozlowski wrote:
> On 25/01/2024 18:11, Oleksij Rempel wrote:
> > On Thu, Jan 25, 2024 at 11:57:18AM +0100, Krzysztof Kozlowski wrote:
> >> On 24/01/2024 13:22, Oleksij Rempel wrote:
> >>> Add device tree bindings that describe hardware implementations of
> >>> Non-Volatile Memory (NVMEM) used for storing Power State Change Reasons
> >>> (PSCR).
> >>> +  that stores Power State Change Reasons (PSCR).
> >>> +
> >>> +allOf:
> >>> +  - $ref: pscrr.yaml#
> >>> +
> >>> +properties:
> >>> +  compatible:
> >>> +    const: pscrr-nvmem
> >>> +
> >>
> >> So that's a driver :/. Maybe Rob will like it, but it's a no from me.
> >> Please come up with something really suiting DEVICES, not DRIVERS.
> > 
> > If I understand your distinction between 'DEVICES' and 'DRIVERS'
> > correctly, 'DEVICES' in the device tree context are meant to represent
> > physical hardware components, while 'DRIVERS' refer to software
> 
> Yes.
> 
> > abstractions of these components. However, there are numerous device
> > tree instances, like software-based implementations for SPI, I2C, or
> > GPIO, which could also be interpreted as 'DRIVERS' in the context of
> 
> True. Yet they are still for physical interfaces. There is no DTS having
> some virtual I2C for a board which does not have I2C.
> 
> > your email. Similarly, the binding for PSCRR represents functionality not
> > fully implemented in hardware but supported by the hardware component of
> > NVMEM, akin to how ramoops or other functionalities are represented.
> 
> You don't need a binding for your case. Instantiate it whatever you wish
> - modprobe for example - and configure through approved kernel
> interfaces - sysfs for example.

About using sysfs for the NVMEM cell, it won't work for my needs because
I have to know about reboot events before the filesystem is ready. So,
I'm thinking of using a boot parameter for the kernel. It would look
like this: pscrr-nvmem.nvmem_cell_alias=nvmem-cell0. This way, I can set
up the NVMEM cell right at the system's start. I'll need to use stable
NVMEM cell names for this. Is it ok to introduce NVMEM cell aliases in
the devicetree?

Best Regards,
Oleksij
Krzysztof Kozlowski Jan. 29, 2024, 7:43 a.m. UTC | #5
On 26/01/2024 17:51, Oleksij Rempel wrote:
> On Fri, Jan 26, 2024 at 10:03:51AM +0100, Krzysztof Kozlowski wrote:
>> On 25/01/2024 18:11, Oleksij Rempel wrote:
>>> On Thu, Jan 25, 2024 at 11:57:18AM +0100, Krzysztof Kozlowski wrote:
>>>> On 24/01/2024 13:22, Oleksij Rempel wrote:
>>>>> Add device tree bindings that describe hardware implementations of
>>>>> Non-Volatile Memory (NVMEM) used for storing Power State Change Reasons
>>>>> (PSCR).
>>>>> +  that stores Power State Change Reasons (PSCR).
>>>>> +
>>>>> +allOf:
>>>>> +  - $ref: pscrr.yaml#
>>>>> +
>>>>> +properties:
>>>>> +  compatible:
>>>>> +    const: pscrr-nvmem
>>>>> +
>>>>
>>>> So that's a driver :/. Maybe Rob will like it, but it's a no from me.
>>>> Please come up with something really suiting DEVICES, not DRIVERS.
>>>
>>> If I understand your distinction between 'DEVICES' and 'DRIVERS'
>>> correctly, 'DEVICES' in the device tree context are meant to represent
>>> physical hardware components, while 'DRIVERS' refer to software
>>
>> Yes.
>>
>>> abstractions of these components. However, there are numerous device
>>> tree instances, like software-based implementations for SPI, I2C, or
>>> GPIO, which could also be interpreted as 'DRIVERS' in the context of
>>
>> True. Yet they are still for physical interfaces. There is no DTS having
>> some virtual I2C for a board which does not have I2C.
>>
>>> your email. Similarly, the binding for PSCRR represents functionality not
>>> fully implemented in hardware but supported by the hardware component of
>>> NVMEM, akin to how ramoops or other functionalities are represented.
>>
>> You don't need a binding for your case. Instantiate it whatever you wish
>> - modprobe for example - and configure through approved kernel
>> interfaces - sysfs for example.
> 
> About using sysfs for the NVMEM cell, it won't work for my needs because
> I have to know about reboot events before the filesystem is ready. So,

initrd can configure it before mounting filesystem.

> I'm thinking of using a boot parameter for the kernel. It would look
> like this: pscrr-nvmem.nvmem_cell_alias=nvmem-cell0. This way, I can set
> up the NVMEM cell right at the system's start. I'll need to use stable
> NVMEM cell names for this. Is it ok to introduce NVMEM cell aliases in
> the devicetree?

In my opinion no, because the point of Devicetree is not to solve your
system init problems. You add pure software node which should not be in
your DTS for many reasons: it is not a hardware description and it is a
 software policy enforced on all users of DTS without actually
consulting them. Also, this solution ignores ACPI systems. Developing a
proper interface would work on ACPI as well.

Best regards,
Krzysztof
diff mbox series

Patch

diff --git a/Documentation/devicetree/bindings/power/reset/pscrr-nvmem.yaml b/Documentation/devicetree/bindings/power/reset/pscrr-nvmem.yaml
new file mode 100644
index 000000000000..779920dea283
--- /dev/null
+++ b/Documentation/devicetree/bindings/power/reset/pscrr-nvmem.yaml
@@ -0,0 +1,53 @@ 
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/power/reset/pscrr-nvmem.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Generic NVMEM Power State Change Reason Recorder
+
+maintainers:
+  - Oleksij Rempel <o.rempel@pengutronix.de>
+
+description: This binding describes the Non-Volatile Memory (NVMEM) hardware
+  that stores Power State Change Reasons (PSCR).
+
+allOf:
+  - $ref: pscrr.yaml#
+
+properties:
+  compatible:
+    const: pscrr-nvmem
+
+  nvmem-cells:
+    description: |
+      A phandle pointing to the nvmem-cells node where the power state change
+      reasons are stored.
+    maxItems: 1
+
+  nvmem-cell-names:
+    items:
+      - const: pscr
+
+  pscr-under-voltage: true
+  pscr-over-current: true
+  pscr-regulator-failure: true
+  pscr-over-temperature: true
+
+required:
+  - compatible
+  - nvmem-cells
+  - nvmem-cell-names
+
+additionalProperties: false
+
+examples:
+  - |
+    power-state-change-reason {
+      compatible = "pscrr-nvmem";
+      nvmem-cells = <&pscr_cell>;
+      nvmem-cell-names = "pscr";
+      pscr-under-voltage = <1>;
+      pscr-over-temperature = <2>;
+    };
+...