[PATCH RFC 02/10] dt-bindings: devfreq: add mt8196-gpufreq binding

Nicolas Frattaroli
2025-09-05T10:24:15Z

On the MediaTek MT8196 SoC, the GPU has its power and frequency
dynamically controlled by an embedded special-purpose MCU. This MCU is
in charge of powering up the GPU silicon. It also provides us with a
list of available OPPs at runtime, and is fully in control of all the
regulator and clock fiddling it takes to reach a certain level of
performance. It's also in charge of enforcing limits on power draw or
temperature.

Add a binding for this device in the devfreq subdirectory, where it
seems to fit in best considering its tasks.

The functions of many of the mailbox channels are unknown. This is not
the fault of this binding's author; we've never received adequate
documentation for this hardware, and the downstream code does not make
use of them in a way that'd reveal their purpose. They are kept in the
binding as the binding should be complete.

Signed-off-by: Nicolas Frattaroli <nicolas.frattaroli@collabora.com>
---
.../bindings/devfreq/mediatek,mt8196-gpufreq.yaml | 116 +++++++++++++++++++++
1 file changed, 116 insertions(+)

diff --git a/Documentation/devicetree/bindings/devfreq/mediatek,mt8196-gpufreq.yaml b/Documentation/devicetree/bindings/devfreq/mediatek,mt8196-gpufreq.yaml
new file mode 100644
index 0000000000000000000000000000000000000000..1fe43c9fc94bb603b1fb77e9a97a27e92fea1ae8
--- /dev/null
+++ b/Documentation/devicetree/bindings/devfreq/mediatek,mt8196-gpufreq.yaml
@@ -0,0 +1,116 @@
+# SPDX-License-Identifier: GPL-2.0-only OR BSD-2-Clause
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/devfreq/mediatek,mt8196-gpufreq.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: MediaTek MFlexGraphics Performance Controller
+
+maintainers:
+ - Nicolas Frattaroli <nicolas.frattaroli@collabora.com>
+
+properties:
+ $nodename:
+ pattern: '^performance-controller@[a-f0-9]+$'
+
+ compatible:
+ enum:
+ - mediatek,mt8196-gpufreq
+
+ reg:
+ items:
+ - description: GPR memory area
+ - description: RPC memory area
+ - description: SoC variant ID register
+
+ reg-names:
+ items:
+ - const: gpr
+ - const: rpc
+ - const: e2_id
+
+ clocks:
+ items:
+ - description: main clock of the embedded controller (EB)
+ - description: core PLL
+ - description: stack 0 PLL
+ - description: stack 1 PLL
+
+ clock-names:
+ items:
+ - const: eb
+ - const: mfgpll
+ - const: mfgpll_sc0
+ - const: mfgpll_sc1
+
+ mboxes:
+ items:
+ - description: FastDVFS events
+ - description: frequency control
+ - description: sleep control
+ - description: timer control
+ - description: frequency hopping control
+ - description: hardware voter control
+ - description: gpumpu (some type of memory control, unknown)
+ - description: FastDVFS control
+ - description: Unknown
+ - description: Unknown
+ - description: Unknown, but likely controls some boosting behaviour
+ - description: Unknown
+
+ mbox-names:
+ items:
+ - const: fast_dvfs_event
+ - const: gpufreq
+ - const: sleep
+ - const: timer
+ - const: fhctl
+ - const: ccf
+ - const: gpumpu
+ - const: fast_dvfs
+ - const: ipir_c_met
+ - const: ipis_c_met
+ - const: brisket
+ - const: ppb
+
+ shmem:
+ $ref: /schemas/types.yaml#/definitions/phandle
+ description: phandle to the shared memory region of the GPUEB MCU
+
+required:
+ - compatible
+ - reg
+ - reg-names
+ - clocks
+ - clock-names
+ - mboxes
+ - mbox-names
+ - shmem
+
+additionalProperties: false
+
+examples:
+ - |
+ #include <dt-bindings/clock/mediatek,mt8196-clock.h>
+
+ gpufreq: performance-controller@4b09fd00 {
+ compatible = "mediatek,mt8196-gpufreq";
+ reg = <0x4b09fd00 0x80>,
+ <0x4b800000 0x1000>,
+ <0x4b860128 0x4>;
+ reg-names = "gpr", "rpc", "e2_id";
+ clocks = <&topckgen CLK_TOP_MFG_EB>,
+ <&mfgpll CLK_MFG_AO_MFGPLL>,
+ <&mfgpll_sc0 CLK_MFGSC0_AO_MFGPLL_SC0>,
+ <&mfgpll_sc1 CLK_MFGSC1_AO_MFGPLL_SC1>;
+ clock-names = "eb", "mfgpll", "mfgpll_sc0",
+ "mfgpll_sc1";
+ mboxes = <&gpueb_mbox 0>, <&gpueb_mbox 1>, <&gpueb_mbox 2>,
+ <&gpueb_mbox 3>, <&gpueb_mbox 4>, <&gpueb_mbox 5>,
+ <&gpueb_mbox 6>, <&gpueb_mbox 7>, <&gpueb_mbox 8>,
+ <&gpueb_mbox 9>, <&gpueb_mbox 10>, <&gpueb_mbox 11>;
+ mbox-names = "fast_dvfs_event", "gpufreq", "sleep", "timer", "fhctl",
+ "ccf", "gpumpu", "fast_dvfs", "ipir_c_met", "ipis_c_met",
+ "brisket", "ppb";
+ shmem = <&gpufreq_shmem>;
+ };

--
2.51.0