14    in-kernel cpufreq scaling driver changes the frequency. Note that this is not
15    supported on all platforms. In our experience it works reliably on ARM-based
16    SoCs but produces no data on most modern Intel-based platforms. This is
17    because recent Intel CPUs use an internal DVFS which is directly controlled
19    Also note that even on ARM-based platforms, the event is emitted only
28    current value in the trace buffer. Works on both Intel and ARM-based
31 On most Android devices the frequency scaling is per-cluster (group of
37 It is possible to record one-off also the full list of frequencies supported by
42 [`cpu_freq` table](/docs/analysis/sql-tables.autogen#cpu_freq).
44 This is not supported on modern Intel platforms for the same aforementioned
56 Idle-ness must not be confused with full device suspend, which is a stronger and
61 highly CPU/SoC specific. At the trace level, the idle state 0 means not-idle,
63 (e.g., single core idle -> full package idle).
70 typically clock-gated in idle states. In those cases the frequency in the trace
78   left-hand side of the trace, or none at all. Perfetto doesn't currently record
81 * Currently the UI doesn't render the cpufreq track if idle states (see below)
82   are not captured. This is a UI-only bug, data is recorded and query-able
85 ### UI  subsection in CPU frequency and idle states
87 In the UI, CPU frequency and idle-ness are shown on the same track. The height
89 state (colored: not-idle, gray: idle). Hovering or clicking a point in the
92 ![](/docs/images/cpu-frequency.png "CPU frequency and idle states in the UI")
97 Note that the cpuidle value 0xffffffff (4294967295) means _back to not-idle_.
106 ---|------|------|------
119 [`cpu_freq` table](/docs/analysis/sql-tables.autogen#cpu_freq).
124 # Event-driven recording of frequency and idle state changes.
154 ### Full-device suspend
160 the highest power-saving state possible (other than full shutdown).
168 * The UI doesn't display clearly the suspended state. When an Android device