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[dm][dvfs] support Dynamic Voltage and Frequency Scaling (DVFS)
1. Support DVFS and finsh cmd, there are 6 governors: - conservative - freedom - performance - powersave - schedutil 2. Support DVFS for SCMI. 3. Port the Cooling device for DVFS. 4. Port the PM with DVFS. Signed-off-by: GuEe-GUI <2991707448@qq.com>
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GuEe-GUI
Rbb666
@@ -34,6 +34,7 @@
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- @subpage page_device_disk
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- @subpage page_device_partitions
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- @subpage page_device_hwcache
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- @subpage page_device_dvfs
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- @subpage page_device_can
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- @subpage page_device_can_dm
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- @subpage page_device_clk
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@@ -0,0 +1,178 @@
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@page page_device_dvfs DVFS
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# Dynamic Voltage and Frequency Scaling (DVFS)
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Headers: **`components/drivers/include/drivers/dvfs.h`**. Core: **`components/drivers/dvfs/dvfs.c`**, governors: **`components/drivers/dvfs/governor/`**, shell: **`components/drivers/dvfs/dvfs_cmd.c`**.
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DVFS selects an **OPP (Operating Performance Point)** — a frequency and supply voltage pair — according to a **governor** policy. The framework owns the OPP table, governor lifecycle, and MSH commands; **BSP or SoC drivers** implement how a given OPP is applied (clock, regulator, firmware calls).
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**Kconfig**: **`RT_USING_DVFS`** (requires **`RT_USING_DM`**, **`RT_USING_CLK`**, **`RT_USING_REGULATOR`**). Optional: **`RT_USING_DVFS_EVENT`**, **`RT_DVFS_SCMI_CPUFREQ`**, and BSP options under **`SOC_DM_DVFS_*`**.
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---
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## Architecture
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```
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Device tree (operating-points-v2, supplies, clocks)
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v
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BSP cpufreq / devfreq driver (SOC_DM_DVFS_CPUFREQ_DIR, …)
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fills rt_dvfs_scaling_ops (set_opp, parse_opp, …)
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v
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rt_dvfs_cpufreq_register() / rt_dvfs_devfreq_register()
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v
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rt_dvfs_scaling (OPP table, cur_freq, governor)
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+-- governor (performance / ondemand / …)
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+-- thermal-cool-dvfs (optional, RT_THERMAL_COOL_DVFS)
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+-- rt_dvfs_scaling_set_frequency() / apply_opp()
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```
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| Layer | Location | Role |
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| --- | --- | --- |
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| Framework | `components/drivers/dvfs/` | OPP table, governors, load stats, PM hooks, MSH |
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| Generic SCMI | `dvfs-scmi-cpufreq.c` | Optional SCMI-based CPUfreq (**`RT_DVFS_SCMI_CPUFREQ`**) |
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| BSP | **`SOC_DM_DVFS_CPUFREQ_DIR`**, **`SOC_DM_DVFS_DEVFREQ_DIR`**, **`SOC_DM_DVFS_EVENT_DIR`** | Platform probe, **`set_opp`**, DT parsing |
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| Thermal | `thermal-cool-dvfs.c` | Map cooling levels to OPP indices — @ref page_device_thermal_cool |
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When **`RT_USING_DVFS`** is enabled, **`struct rt_device::dvfs_scaling`** links a device to its scaling domain for **`list_dvfs`** / **`dvfs dump`**.
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---
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## Registering a scaling domain (BSP driver)
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Typical CPU path:
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1. Allocate **`struct rt_dvfs_cpufreq`** (embeds **`struct rt_dvfs_scaling`**).
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2. Fill **`scaling->ops`** — at minimum **`set_opp`** and **`parse_opp`** for DT-backed OPP tables.
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3. Obtain **`scaling->clk`** and **`scaling->supply`** from the CPU / cluster device node.
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4. Parse OPP nodes ( **`operating-points-v2`** ) into the scaling OPP table.
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5. Call **`rt_dvfs_cpufreq_register()`**, then **`rt_dvfs_scaling_set_governor()`** with the desired default governor.
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Devfreq devices follow the same pattern with **`struct rt_dvfs_devfreq`** and optional **`struct rt_dvfs_event`** for load feedback (**`RT_USING_DVFS_EVENT`**).
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If the driver does not provide **`ops->set_opp`**, the framework falls back to a generic sequence using **`rt_clk_set_rate`** and **`rt_regulator_set_voltage`** on **`scaling->clk`** / **`scaling->supply`**.
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---
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## Governors
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| Name | Behavior |
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| --- | --- |
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| **`performance`** | Always **`max_freq`** |
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| **`powersave`** | Always **`min_freq`** |
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| **`freedom`** | No automatic changes; user sets frequency manually |
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| **`ondemand`** | Periodic load sampling; high load → max, low load → scaled down |
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| **`conservative`** | Step up/down by **`freq_step`** |
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| **`schedutil`** | Target frequency proportional to estimated load |
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Dynamic governors depend on **`RT_USING_IDLE_HOOK`** (load estimation) and **`RT_USING_SYSTEM_WORKQUEUE`** (monitor timer). The default governor is chosen by the BSP driver at registration time.
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Governor parameters (**`up_threshold`**, **`sampling_rate_ms`**, …) live in **`struct rt_dvfs_governor_params`** and can be adjusted via **`rt_dvfs_governor_set_params()`**.
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---
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## MSH commands
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Requires **`RT_USING_CONSOLE`** and **`RT_USING_MSH`** (**`dvfs_cmd.c`**).
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```text
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list_dvfs
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dvfs dump <name>
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dvfs set_governor <name> <governor>
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dvfs set_frequency <name> <Hz>
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```
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**`set_frequency`** switches to **`freedom`** automatically when the active governor is not freedom.
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Example:
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```text
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msh />dvfs set_governor cpu0 performance
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msh />dvfs dump cpu0
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```
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The scaling device **`<name>`** is assigned by the BSP driver (commonly **`cpufreq0`**, **`dmc`**, etc.).
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---
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## Device tree (typical CPU)
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Minimal pattern (details vary by SoC BSP):
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```dts
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cpu0: cpu@0 {
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device_type = "cpu";
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compatible = "arm,cortex-a55";
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operating-points-v2 = <&cpu0_opp_table>;
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cpu-supply = <&cpu_reg>;
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/* optional: #cooling-cells for thermal-cool-dvfs */
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};
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cpu0_opp_table: opp-table {
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compatible = "operating-points-v2";
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opp-1000000000 {
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opp-hz = /bits/ 64 <1000000000>;
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opp-microvolt = <900000>;
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};
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/* additional OPP nodes … */
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};
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```
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| Binding | Role |
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| --- | --- |
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| **`operating-points-v2`** | OPP table phandle on the scaling device |
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| **`opp-hz` / `opp-microvolt`** | Frequency (Hz) and voltage (µV) per OPP |
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| **`*-supply`** | Regulator phandle(s) used when scaling voltage |
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| **`#cooling-cells`** | Enables **`dvfs-cool`** thermal device on the CPU node |
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Passive thermal **`cooling-maps`** can reference the DVFS cooling device to cap OPP on trip — see @ref page_device_thermal_cool.
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---
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## Kconfig
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| Option | Role |
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| --- | --- |
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| **`RT_USING_DVFS`** | Core framework + governors |
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| **`RT_USING_DVFS_EVENT`** | **`dvfs_event.c`**, devfreq load via event devices |
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| **`RT_USING_DVFS_OPP_RETRY_MAX`** | Retries on **`-RT_EBUSY`** during OPP transition |
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| **`RT_DVFS_SCMI_CPUFREQ`** | Generic **`dvfs-scmi-cpufreq.c`** |
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| **`RT_THERMAL_COOL_DVFS`** | **`thermal-cool-dvfs.c`** (also needs **`RT_USING_THERMAL`**) |
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| **`RT_USING_IDLE_HOOK`** | Required for meaningful dynamic governor load stats |
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| **`SOC_DM_DVFS_CPUFREQ_DIR`** | BSP CPUfreq driver(s) |
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| **`SOC_DM_DVFS_DEVFREQ_DIR`** | BSP devfreq driver(s) |
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| **`SOC_DM_DVFS_EVENT_DIR`** | BSP devfreq event source(s) |
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---
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## OPP transition order
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When **`ops->set_opp`** is provided, the BSP defines the safe ramp sequence ( voltage-before-frequency on scale-up, etc.).
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When the framework generic path is used (**`dvfs.c`**):
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- **Scale up**: raise voltage (if needed) → optional **`transition_latency`** delay → **`rt_clk_set_rate`**
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- **Scale down**: lower clock rate → lower voltage (if needed)
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On failure, **`cur_freq`** and **`current_opp`** are not updated. **`RT_USING_DVFS_OPP_RETRY_MAX`** controls busy retries on regulator or clock calls.
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---
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## Pitfalls
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- **BSP `set_opp` must match hardware**: clocks, regulators, and any bus used to change voltage must remain usable across the full OPP range. Broken I2C/SPI/regulator access during a transition surfaces as stuck frequency or **`-RT_EBUSY`** retries.
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- **Governor switch vs. pending work**: dynamic governors schedule work on the system workqueue. After **`set_governor`**, monitor callbacks must verify the active governor type before changing frequency (see governor sources).
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- **Thermal cooling levels**: **`thermal-cool-dvfs`** maps cooling **level** to an OPP index; releasing cooling must restore full performance (highest OPP), not the most restrictive level. See **`rt_thermal_cooling_device_kick`** in **`thermal.c`**.
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- **Verifying dynamic governors**: do not run a tight CPU loop inside the **FinSH / shell thread** — it usually has higher priority than the system workqueue and can prevent load sampling. Use a **separate background thread** at lower priority, or compare **`performance`** vs **`powersave`** (static governors) to confirm the scaling path works before testing **`ondemand`** / **`schedutil`**.
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---
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## Related pages
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- @ref page_device_clk — **`rt_clk_set_rate`**, consumer clock API
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- @ref page_device_regulator — supply rails referenced from OPP / CPU nodes
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- @ref page_device_scmi — SCMI clock/regulator when firmware owns scaling resources
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- @ref page_device_thermal_cool — **`thermal-cool-dvfs`**
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@@ -213,7 +213,7 @@ Call **`update`** from the zone poller (automatic after register) or manually fo
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| **`thermal-scmi.c`** | **`RT_SCMI_DRIVER_EXPORT`**, protocol sensor `"thermal"` | One zone per SCMI temperature sensor |
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| **`thermal-cool-pwm-fan.c`** | **`compatible = "pwm-fan"`** | PWM + optional regulator — @ref page_device_thermal_cool |
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| **`thermal-cool-gpio-fan.c`** | GPIO + speed table | Discrete fan speeds |
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| **`thermal-cool-dvfs.c`** | DVFS OPP levels as cooling steps | Throttle CPU/GPU via @ref page_device_clk / DVFS |
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| **`thermal-cool-dvfs.c`** | DVFS OPP levels as cooling steps | Throttle CPU/GPU via @ref page_device_dvfs |
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BSP sensors (e.g. board thermal IC) typically **`rt_thermal_zone_device_register`** in platform **`probe`** after filling trips in code or relying entirely on **`thermal_ofw_setup`**.
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@@ -251,6 +251,7 @@ Constants: **`RT_THERMAL_TEMP_INVALID`** (−274000), **`RT_THERMAL_NO_LIMIT`**.
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## See also
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- @ref page_device_thermal_cool — PWM fan cooling device
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- @ref page_device_dvfs — DVFS framework and Rockchip cpufreq
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- @ref page_device_scmi — SCMI sensor protocol
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- @ref page_device_pwm
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- @ref page_device_regulator
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