[PATCH v5 1/4] dt-bindings: clock: google,gs101-clock: add samsung,sysreg property as required

Peter Griffin
2025-11-14T14:17:03Z

Each CMU (with the exception of cmu_top) has a corresponding sysreg bank
that contains the BUSCOMPONENT_DRCG_EN and optional MEMCLK registers.
The BUSCOMPONENT_DRCG_EN register enables dynamic root clock gating of
bus components and MEMCLK gates the sram clock.

Now the clock driver supports automatic clock mode, to fully enable dynamic
root clock gating it is required to configure these registers. Update the
bindings documentation so that all CMUs (with the exception of
gs101-cmu-top) have samsung,sysreg as a required property.

Note this is NOT an ABI break, as if the property isn't specified the
clock driver will fallback to the current behaviour of not initializing
the registers. The system still boots, but bus components won't benefit
from dynamic root clock gating and dynamic power will be higher (which has
been the case until now anyway).

Additionally update the DT example to included the correct CMU size as
registers in that region are used for automatic clock mode.

Signed-off-by: Peter Griffin <peter.griffin@linaro.org>
---
Changes in v5:
- Invert the test for google,gs101-cmu-top (Andre)

Changes in v4
- Update commit description with additional requested details (Krzysztof)

Changes in v3:
- Update commit description as to why the sysreg is required (Krzysztof)

Changes in v2:
- Update commit description regarding updated example (Andre)
---
.../devicetree/bindings/clock/google,gs101-clock.yaml | 19 ++++++++++++++++++-
1 file changed, 18 insertions(+), 1 deletion(-)

diff --git a/Documentation/devicetree/bindings/clock/google,gs101-clock.yaml b/Documentation/devicetree/bindings/clock/google,gs101-clock.yaml
index 31e106ef913dead9a038b3b6d8b43b950587f6aa..09e679c1a9def03d53b8b493929911ea902a1763 100644
--- a/Documentation/devicetree/bindings/clock/google,gs101-clock.yaml
+++ b/Documentation/devicetree/bindings/clock/google,gs101-clock.yaml
@@ -52,6 +52,11 @@ properties:
reg:
maxItems: 1

+ samsung,sysreg:
+ $ref: /schemas/types.yaml#/definitions/phandle
+ description:
+ Phandle to system registers interface.
+
required:
- compatible
- "#clock-cells"
@@ -166,6 +171,18 @@ allOf:
- const: bus
- const: ip

+ - if:
+ properties:
+ compatible:
+ contains:
+ const: google,gs101-cmu-top
+ then:
+ properties:
+ samsung,sysreg: false
+ else:
+ required:
+ - samsung,sysreg
+
additionalProperties: false

examples:
@@ -175,7 +192,7 @@ examples:

cmu_top: clock-controller@1e080000 {
compatible = "google,gs101-cmu-top";
- reg = <0x1e080000 0x8000>;
+ reg = <0x1e080000 0x10000>;
#clock-cells = <1>;
clocks = <&ext_24_5m>;
clock-names = "oscclk";

--
2.52.0.rc1.455.g30608eb744-goog