[PATCH 1/6] dt-bindings: mfd: add binding for Apple Mac System Management Controller

[Russell King (Oracle)]

On Thu, Sep 01, 2022 at 06:45:52PM +0300, Krzysztof Kozlowski wrote:
> On 01/09/2022 18:24, Russell King (Oracle) wrote:
> > On Thu, Sep 01, 2022 at 06:15:46PM +0300, Krzysztof Kozlowski wrote:
> >> On 01/09/2022 18:12, Russell King (Oracle) wrote:
> >>>>> +  compatible:
> >>>>> +    items:
> >>>>> +      - enum:
> >>>>> +        - apple,t8103-smc
> >>>>
> >>>> You miss two spaces of indentation on this level.
> >>>
> >>> Should that be picked up by the dt checker?
> >>
> >> I think yamllint complains about it. It is not a hard-dependency, so
> >> maybe you don't have it installed.
> >>
> >>>
> >>>>> +        - apple,t8112-smc
> >>>>> +        - apple,t6000-smc
> >>>>
> >>>> Bring some order here - either alphabetical or by date of release (as in
> >>>> other Apple schemas). I think t6000 was before t8112, so it's none of
> >>>> that orders.
> >>>
> >>> Ok.
> >>>
> >>>>> +      - const: apple,smc
> >>>>> +
> >>>>> +  reg:
> >>>>> +    description: Two regions, one for the SMC area and one for the SRAM area.
> >>>>
> >>>> You need constraints for size/order, so in this context list with
> >>>> described items.
> >>>
> >>> How do I do that? I tried maxItems/minItems set to 2, but the dt checker
> >>> objected to it.
> >>
> >> One way:
> >> reg:
> >>   items:
> >>     - description: SMC area
> >>     - description: SRAM area
> >>
> >> but actually this is very similar what you wrote for reg-names - kind of
> >> obvious, so easier way:
> >>
> >> reg:
> >>   maxItems: 2
> > 
> > Doesn't work. With maxItems: 2, the example fails, yet it correctly lists
> > two regs which are 64-bit address and 64-bit size - so in total 8 32-bit
> > ints.
> > 
> > Documentation/devicetree/bindings/mfd/apple,smc.example.dtb: smc at 23e400000: reg: [[2, 1044381696], [0, 16384], [2, 1071644672], [0, 1048576]] is too long
> >         From schema: /home/rmk/git/linux-rmk/Documentation/devicetree/bindings/mfd/apple,smc.yaml
> > 
> > Hence, I originally had maxItems: 2, and ended up deleting it because of
> > the dt checker.
> > 
> > With the two descriptions, it's the same failure.
> 
> Yeah, they should create same result.
> 
> > 
> > I think the problem is that the checker has no knowledge in the example
> > of how big each address and size element of the reg property is. So,
> > it's interpreting it as four entries of 32-bit address,size pairs
> > instead of two entries of 64-bit address,size pairs. Yep, that's it,
> > if I increase the number of "- description" entries to four then it's
> > happy.
> > 
> > So, what's the solution?
> > 
> 
> If you open generated DTS examples (in your
> kbuild-output/Documentation/devicetree/bindings/mfd/) you will see which
> address/size cells are expected. By default it is I think address/size
> cells=1, so you need a bus node setting it to 2.

Thanks, that works. The patch with all those points addressed now looks
like:

8<===
From: "Russell King (Oracle)" <rmk+kernel at armlinux.org.uk>
Subject: [PATCH] dt-bindings: mfd: add binding for Apple Mac System Management
 Controller

Add a DT binding for the Apple Mac System Management Controller.

Signed-off-by: Russell King (Oracle) <rmk+kernel at armlinux.org.uk>
---
 .../devicetree/bindings/mfd/apple,smc.yaml    | 61 +++++++++++++++++++
 1 file changed, 61 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/mfd/apple,smc.yaml

diff --git a/Documentation/devicetree/bindings/mfd/apple,smc.yaml b/Documentation/devicetree/bindings/mfd/apple,smc.yaml
new file mode 100644
index 000000000000..168f237c2962
--- /dev/null
+++ b/Documentation/devicetree/bindings/mfd/apple,smc.yaml
@@ -0,0 +1,61 @@
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/mfd/apple,smc.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Apple Mac System Management Controller
+
+maintainers:
+  - Hector Martin <marcan at marcan.st>
+
+description:
+  Apple Mac System Management Controller implements various functions
+  such as GPIO, RTC, power, reboot.
+
+properties:
+  compatible:
+    items:
+      - enum:
+          - apple,t6000-smc
+          - apple,t8103-smc
+          - apple,t8112-smc
+      - const: apple,smc
+
+  reg:
+    items:
+      - description: SMC area
+      - description: SRAM area
+
+  reg-names:
+    items:
+      - const: smc
+      - const: sram
+
+  mboxes:
+    maxItems: 1
+    description:
+      A phandle to the mailbox channel
+
+additionalProperties: false
+
+required:
+  - compatible
+  - reg
+  - reg-names
+  - mboxes
+
+examples:
+  - |
+    soc {
+      #address-cells = <2>;
+      #size-cells = <2>;
+
+      smc at 23e400000 {
+        compatible = "apple,t8103-smc", "apple,smc";
+        reg = <0x2 0x3e400000 0x0 0x4000>,
+               <0x2 0x3fe00000 0x0 0x100000>;
+        reg-names = "smc", "sram";
+        mboxes = <&smc_mbox>;
+      };
+    };
-- 
2.30.2


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