[PATCH v5] dt-bindings: clock: via,vt8500: Convert to DT Schema

[PATCH v5] dt-bindings: clock: via,vt8500: Convert to DT Schema

[Udaya Kiran Challa]

Convert the VIA/Wondermedia VT8500 and Wondermedia WM8xxx series SoCs clock
controller binding from the legacy text format to DT schema.

Signed-off-by: Udaya Kiran Challa <challauday369@gmail.com>
---
Changelog:
Changes since v4:
- Remove schema select matching for via,vt8500-pmc
- Add dependentRequired validation for divisor-mask
- Fix maintainers list
- Add reg false condition for device clock
- Fix example validation against clocks child node

Link to v4:https://lore.kernel.org/all/20260524151110.21277-1-challauday369@gmail.com/

Changes since v3:
- Add schema select matching for via,vt8500-pmc
- Allow hyphen in node names under patternProperties
- Add dependentRequired validation for enable-reg/enable-bit
- Fix example validation against PMC schema

Link to v3:https://lore.kernel.org/all/20260524111813.39810-1-challauday369@gmail.com/

Changes since v2:
- Drop redundant description for clocks
- Disable reg property for device clocks
- Fix schema hierarchy to match actual DTS structure

Link to v2:https://lore.kernel.org/all/20260521170810.19702-1-challauday369@gmail.com/

Changes since v1:
- Add default value for divisor-mask
- Add required properties compatible and model
- Fix example node name
- Update example size cells and reg value

Link to v1:https://lore.kernel.org/all/20260520025131.17772-1-challauday369@gmail.com/
---
 .../bindings/clock/via,vt8500-clock.yaml      | 133 ++++++++++++++++++
 .../devicetree/bindings/clock/vt8500.txt      |  74 ----------
 2 files changed, 133 insertions(+), 74 deletions(-)
 create mode 100644 Documentation/devicetree/bindings/clock/via,vt8500-clock.yaml
 delete mode 100644 Documentation/devicetree/bindings/clock/vt8500.txt

diff --git a/Documentation/devicetree/bindings/clock/via,vt8500-clock.yaml b/Documentation/devicetree/bindings/clock/via,vt8500-clock.yaml
new file mode 100644
index 000000000000..e2e674d95654
--- /dev/null
+++ b/Documentation/devicetree/bindings/clock/via,vt8500-clock.yaml
@@ -0,0 +1,133 @@
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/clock/via,vt8500-clock.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: VIA/Wondermedia VT8500 Clock Controller
+
+maintainers:
+  - Alexey Charkov <alchark@gmail.com>
+  - Krzysztof Kozlowski <krzk@kernel.org>
+
+description:
+  Clock controller bindings for VIA/Wondermedia VT8500 and Wondermedia WM8xxx
+  series SoCs.
+
+properties:
+  compatible:
+    enum:
+      - via,vt8500-pll-clock
+      - wm,wm8650-pll-clock
+      - wm,wm8750-pll-clock
+      - wm,wm8850-pll-clock
+      - via,vt8500-device-clock
+
+  reg:
+    description: Offset of the PLL register within the PMC register space.
+    maxItems: 1
+
+  clocks:
+    maxItems: 1
+
+  "#clock-cells":
+    const: 0
+
+  clock-output-names:
+    maxItems: 1
+
+  enable-reg:
+    description: Offset of the clock enable register within the PMC register space.
+    $ref: /schemas/types.yaml#/definitions/uint32
+
+  enable-bit:
+    description: Bit index controlling clock enable.
+    $ref: /schemas/types.yaml#/definitions/uint32
+    maximum: 31
+
+  divisor-reg:
+    description: Offset of the clock divisor register within the PMC register space.
+    $ref: /schemas/types.yaml#/definitions/uint32
+
+  divisor-mask:
+    description: Bitmask describing the divisor field inside divisor-reg.
+    $ref: /schemas/types.yaml#/definitions/uint32
+    default: 0x1f
+
+required:
+  - compatible
+  - clocks
+  - "#clock-cells"
+
+allOf:
+  - if:
+      properties:
+        compatible:
+          const: via,vt8500-device-clock
+    then:
+      properties:
+        reg: false
+      anyOf:
+        - required:
+            - enable-reg
+            - enable-bit
+        - required:
+            - divisor-reg
+  - if:
+      properties:
+        compatible:
+          enum:
+            - via,vt8500-pll-clock
+            - wm,wm8650-pll-clock
+            - wm,wm8750-pll-clock
+            - wm,wm8850-pll-clock
+    then:
+      required:
+        - reg
+
+dependentRequired:
+  enable-reg:
+    - enable-bit
+  enable-bit:
+    - enable-reg
+  divisor-mask:
+    - divisor-reg
+
+additionalProperties: false
+
+examples:
+  - |
+    clocks {
+        #address-cells = <1>;
+        #size-cells = <0>;
+
+        ref25: clock-25000000 {
+            compatible = "fixed-clock";
+            clock-frequency = <25000000>;
+            #clock-cells = <0>;
+        };
+
+        plla: clock@200 {
+            compatible = "wm,wm8650-pll-clock";
+            reg = <0x200>;
+            clocks = <&ref25>;
+            #clock-cells = <0>;
+        };
+
+        pllb: clock@204 {
+            compatible = "wm,wm8650-pll-clock";
+            reg = <0x204>;
+            clocks = <&ref25>;
+            #clock-cells = <0>;
+        };
+
+        clksdhc: sdhc {
+            compatible = "via,vt8500-device-clock";
+            clocks = <&pllb>;
+            #clock-cells = <0>;
+            divisor-reg = <0x328>;
+            divisor-mask = <0x3f>;
+            enable-reg = <0x254>;
+            enable-bit = <18>;
+        };
+    };
diff --git a/Documentation/devicetree/bindings/clock/vt8500.txt b/Documentation/devicetree/bindings/clock/vt8500.txt
deleted file mode 100644
index 91d71cc0314a..000000000000
--- a/Documentation/devicetree/bindings/clock/vt8500.txt
+++ /dev/null
@@ -1,74 +0,0 @@
-Device Tree Clock bindings for arch-vt8500
-
-This binding uses the common clock binding[1].
-
-[1] Documentation/devicetree/bindings/clock/clock-bindings.txt
-
-Required properties:
-- compatible : shall be one of the following:
-	"via,vt8500-pll-clock" - for a VT8500/WM8505 PLL clock
-	"wm,wm8650-pll-clock" - for a WM8650 PLL clock
-	"wm,wm8750-pll-clock" - for a WM8750 PLL clock
-	"wm,wm8850-pll-clock" - for a WM8850 PLL clock
-	"via,vt8500-device-clock" - for a VT/WM device clock
-
-Required properties for PLL clocks:
-- reg : shall be the control register offset from PMC base for the pll clock.
-- clocks : shall be the input parent clock phandle for the clock. This should
-	be the reference clock.
-- #clock-cells : from common clock binding; shall be set to 0.
-
-Required properties for device clocks:
-- clocks : shall be the input parent clock phandle for the clock. This should
-	be a pll output.
-- #clock-cells : from common clock binding; shall be set to 0.
-
-
-Device Clocks
-
-Device clocks are required to have one or both of the following sets of
-properties:
-
-
-Gated device clocks:
-
-Required properties:
-- enable-reg : shall be the register offset from PMC base for the enable
-	register.
-- enable-bit : shall be the bit within enable-reg to enable/disable the clock.
-
-
-Divisor device clocks:
-
-Required property:
-- divisor-reg : shall be the register offset from PMC base for the divisor
-	register.
-Optional property:
-- divisor-mask : shall be the mask for the divisor register. Defaults to 0x1f
-	if not specified.
-
-
-For example:
-
-ref25: ref25M {
-	#clock-cells = <0>;
-	compatible = "fixed-clock";
-	clock-frequency = <25000000>;
-};
-
-plla: plla {
-	#clock-cells = <0>;
-	compatible = "wm,wm8650-pll-clock";
-	clocks = <&ref25>;
-	reg = <0x200>;
-};
-
-sdhc: sdhc {
-	#clock-cells = <0>;
-	compatible = "via,vt8500-device-clock";
-	clocks = <&pllb>;
-	divisor-reg = <0x328>;
-	divisor-mask = <0x3f>;
-	enable-reg = <0x254>;
-	enable-bit = <18>;
-};
-- 
2.43.0

Re: [PATCH v5] dt-bindings: clock: via,vt8500: Convert to DT Schema

[Alexey Charkov]

On Sun, May 31, 2026 at 9:11 PM Udaya Kiran Challa
<challauday369@gmail.com> wrote:
>
> Convert the VIA/Wondermedia VT8500 and Wondermedia WM8xxx series SoCs clock
> controller binding from the legacy text format to DT schema.
>
> Signed-off-by: Udaya Kiran Challa <challauday369@gmail.com>
> ---

Hi,

I'm not sure that this separation of the clock controller binding vs.
PMC is the right way to go (yes, I know it's been that way in the .txt
document, but still).

The clock controller is not a standalone device on these SoCs - it's
one of the functions of the PMC (weirdly enough), with its MMIO space
interweaved between clock statuses and enable controls,
reset/hibernation control, system timer and watchdog, then again clock
control. You can't run the clock controller separately from the
resources provided in its parent PMC node, because all those *reg
nodes are just offsets into the PMC controller's MMIO space. So the
way it's done currently doesn't look like idiomatic DT to me.

If I were to implement support for all that beauty today, I would have
made a top-level MFD node owning the whole MMIO range of the PMC, put
clock IDs into a dt-bindings header file and just implement all clock
operations in code without putting those offsets and bits into the
device tree. They are not configurable, they are not board specific,
they just constitute the interface of a particular SoC revision which
follows directly from a SoC versioned PMC compatible string.

The only thing that would have showed up in the DT then would have
been the PMC node with a register range and a bunch of named
interrupts (not for clocks, but for other functions), a
clock-controller attribute and a single clock cell to pass arbitrarily
assigned clock IDs from a new per-SoC dt-bindings header.

I'm pretty sure there are no users of these DTs outside of mainline
Linux, because vendor kernels used board files, and no DT-enabled
firmware has ever been created, thus the only way to boot these boards
with a device tree has only ever been via an appended-DTB uImage (i.e.
the DTB always comes from the currently used Linux kernel source).
From this perspective I believe redoing the DT in a more
hardware-aligned fashion (and breaking DT ABI) could be better than
making the current suboptimal approach more "official" by encoding it
in DT schema. Krzysztof will likely disagree though :)

Best regards,
Alexey

Re: [PATCH v5] dt-bindings: clock: via,vt8500: Convert to DT Schema

[Krzysztof Kozlowski]

On Sun, May 31, 2026 at 10:39:55PM +0530, Udaya Kiran Challa wrote:
> Convert the VIA/Wondermedia VT8500 and Wondermedia WM8xxx series SoCs clock
> controller binding from the legacy text format to DT schema.
> 
> Signed-off-by: Udaya Kiran Challa <challauday369@gmail.com>
> ---
> Changelog:
> Changes since v4:

My comments from v2 still apply. Almost all of them.

You a PMC binding and preferrably all this goes to that binding.

Best regards,
Krzysztof

Re: [PATCH v5] dt-bindings: clock: via,vt8500: Convert to DT Schema

[Uday Kiran]

> > Convert the VIA/Wondermedia VT8500 and Wondermedia WM8xxx series SoCs clock
> > controller binding from the legacy text format to DT schema.
> >
> > Signed-off-by: Udaya Kiran Challa <challauday369@gmail.com>
> > ---
> > Changelog:
> > Changes since v4:
>
> My comments from v2 still apply. Almost all of them.
>
> You a PMC binding and preferrably all this goes to that binding.

Understood, Krzysztof!

The current separation between the PMC binding and the clock binding may not
reflect the hardware correctly, since the clock controller functionality is
implemented as part of the PMC and all clock-specific registers are offsets
within the PMC register space.

Request you to please confirm on the below points to proceed for next revision
of YAML conversion.

1. It will be a standalone PMC schema (`via,vt8500-pmc.yaml`) which also
describes the clock-related child nodes and replaces both legacy text bindings
(clock.txt & pmc.txt) , or
2. As per Alexey, PMC compatibles should be expanded to per-SoC values.

If it has to be expanded to per-SoC values, can it be taken as separate DT-ABI
change or should be done in the same series now?

Regards,
Udaya Kiran Challa