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154 lines
5.1 KiB
154 lines
5.1 KiB
# Power data sources
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On Android Perfetto bundles data sources to retrieve power
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counters from the device power management units (where supported).
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## Battery counters
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_This data source has been introduced in Android 10 (Q) and requires the
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presence of power-management hardware on the device. This is available on
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most Google Pixel smartphones._
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Modern smartphones are equipped with a power monitoring IC which is able to
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measure the charge flowing in and out of the battery. This allows Perfetto to
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observe the total and instantaneous charge drained from the battery by the
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overall device (the union of SoC, display, radios and all other hardware
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units).
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A simplified block diagram:
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These counters report:
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* The remaining battery capacity in %.
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* The remaining battery charge in microampere-hours (µAh).
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* The instantaneous (typically the average over a small window of time) current
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in microampere (µA)
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The presence and the resolution of these counters depends on the device
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manufacturer. At the platform level this data is obtained polling the
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Android [IHealth HAL][health-hal].
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For more details on HW specs and resolution see
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[Measuring Device Power](https://source.android.com/devices/tech/power/device).
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[health-hal]: https://cs.android.com/android/platform/superproject/+/master:hardware/interfaces/health/2.0/IHealth.hal?q=IHealth
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#### Measuring charge while plugged on USB
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Battery counters measure the charge flowing *in* and *out* of
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the battery. If the device is plugged to a USB cable, you will likely observe
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a negative instantaneous current and an increase of the total charge, denoting
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the fact that charge is flowing in the battery (i.e. charging it) rather
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than out.
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This can make measurements in lab settings problematic. The known workarounds
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for this are:
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* Using specialized USB hubs that allow to electrically disconnect the USB ports
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from the host side. This allows to effectively disconnect the phone while the
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tests are running.
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* On rooted phones the power management IC driver allows to disconnect the USB
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charging while keeping the USB data link active. This feature is
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SoC-specific, is undocumented and not exposed through any HAL.
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For instance on a Pixel 2 this can be achieved running, as root:
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`echo 1 > /sys/devices/soc/800f000.qcom,spmi/spmi-0/spmi0-02/800f000.qcom,spmi:qcom,pmi8998@2:qcom,qpnp-smb2/power_supply/battery/input_suspend`.
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Note that in most devices the kernel USB driver holds a wakelock to keep the
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USB data link active, so the device will never fully suspend even when turning
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the screen off.
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### UI
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### SQL
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```sql
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select ts, t.name, value from counter as c left join counter_track t on c.track_id = t.id
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```
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ts | name | value
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---|------|------
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338297039804951 | batt.charge_uah | 2085000
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338297039804951 | batt.capacity_pct | 75
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338297039804951 | batt.current_ua | -1469687
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338297145212097 | batt.charge_uah | 2085000
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338297145212097 | batt.capacity_pct | 75
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338297145212097 | batt.current_ua | -1434062
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### TraceConfig
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Trace proto:
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[BatteryCounters](/docs/reference/trace-packet-proto.autogen#BatteryCounters)
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Config proto:
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[AndroidPowerConfig](/docs/reference/trace-config-proto.autogen#AndroidPowerConfig)
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Sample config:
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```protobuf
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data_sources: {
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config {
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name: "android.power"
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android_power_config {
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battery_poll_ms: 250
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battery_counters: BATTERY_COUNTER_CAPACITY_PERCENT
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battery_counters: BATTERY_COUNTER_CHARGE
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battery_counters: BATTERY_COUNTER_CURRENT
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}
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}
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}
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```
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## Power rails
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_This data source has been introduced in Android 10 (Q) and requires the
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dedicated hardware on the device. This hardware is not yet available on
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most production phones._
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Recent version of Android introduced the support for more advanced power
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monitoring at the hardware subsystem level, known as "Power rail counters".
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These counters measure the energy drained by (groups of) hardware units.
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Unlike the battery counters, they are not affected by the charging/discharging
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state of the battery, because they measure power downstream of the battery.
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The presence and the resolution of power rail counters depends on the device
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manufacturer. At the platform level this data is obtained polling the
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Android [IPowerStats HAL][power-hal].
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[power-hal]: https://cs.android.com/android/platform/superproject/+/master:hardware/interfaces/power/stats/1.0/IPowerStats.hal
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Simplified block diagram:
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### TraceConfig
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Trace proto:
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[PowerRails](/docs/reference/trace-packet-proto.autogen#PowerRails)
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Config proto:
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[AndroidPowerConfig](/docs/reference/trace-config-proto.autogen#AndroidPowerConfig)
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Sample config:
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```protobuf
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data_sources: {
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config {
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name: "android.power"
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android_power_config {
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battery_poll_ms: 250
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collect_power_rails: true
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# Note: it is possible to specify both rails and battery counters
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# in this section.
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}
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}
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}
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```
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## Related data sources
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See also the [CPU -> Frequency scaling](cpu-freq.md) data source.
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