DPLL(8)

📦
version 7.3.0 · 4 versions
, in arch rolling, nixpkgs unstable, ubuntu stonking

✨ DPLL(8) — dpll 💖

okay bestie, welcome to the DPLL(8) manual page, and no cap, this one is a whole vibe. The star? It's dpll, the Digital Phase Locked Loop subsystem management tool. Let's get into it.

🌸 NAME 🌸

dpll — Digital Phase Locked Loop (DPLL) subsystem management. That's the name line, iconic, periodt.

🦋 SYNOPSIS 🦋

dpll [ OPTIONS ] device { COMMAND | help }

dpll [ OPTIONS ] pin { COMMAND | help }

dpll [ OPTIONS ] monitor

OPTIONS := { -V | --Version | -j | --json | -p | --pretty | -t |
        --timestamp | --tshort }

💅 DESCRIPTION 💅

The dpll utility is used to configure and monitor Digital Phase Locked Loop (DPLL) devices and pins. DPLLs are used for clock synchronization in various hardware, particularly in telecommunications and networking equipment.

A DPLL device can lock to one or more input pins and provide synchronized output. Pins can be physical external signals (like GNSS 1PPS, SyncE), or internal oscillators.

✨ OPTIONS ✨

  • -V, --Version — Print the version of the dpll utility and exit. Slay, short and sweet.
  • -j, --json — Output results in JavaScript Object Notation (JSON).
  • -p, --pretty — When combined with -j, generates a pretty JSON output with indentation and newlines for better human readability.
  • -t, --timestamp — When used with the monitor object, print a Timestamp: line before each received notification, in the same format used by ip monitor.
  • --tshort — Like -t, but emits a more compact, ISO 8601 inline prefix [YYYY-MM-DDTHH:MM:SS.uuuuuu] in front of each notification instead of a separate Timestamp: line.

👑 DEVICE COMMANDS 👑

🎀 dpll device show 🎀

dpll device show [ id ID ] [ module-name NAME ] [ clock-id ID ] [ type TYPE ] [ mode MODE ] [ lock-status STATUS ]

Display information about DPLL devices. If no arguments are specified, shows all devices in the system.

  • id ID — Show only the device with the specified numeric identifier.
  • module-name NAME — Show only devices provided by the specified kernel module.
  • clock-id ID — Show only devices with the specified 64-bit clock identifier.
  • type TYPE — Show only devices of the specified type: pps or eec.
  • mode MODE — Show only devices in the specified operating mode: manual or automatic.
  • lock-status STATUS — Show only devices with the specified lock status: unlocked, locked, locked-ho-acq, holdover.

Output includes:

  • Device ID
  • Module name providing the device
  • Clock ID (unique identifier)
  • Operating mode (manual, automatic)
  • Lock status (unlocked, locked, locked-ho-acq, holdover)
  • Lock status error (if present)
  • Clock quality level (if supported)
  • Temperature (if supported)
  • Type (PPS or EEC)
  • Supported modes
  • Phase offset monitor status (enable/disable)
  • Phase offset averaging factor
  • Frequency monitor status (enable/disable)

🧚 dpll device set 🧚

dpll device set id ID [ PARAMETER VALUE ] ...

Configure DPLL device parameters.

  • id ID — Specifies which device to configure (required).
  • mode { automatic | manual } — Set the operating mode of the DPLL device. In automatic mode, the DPLL autonomously selects the best available input source based on priority and quality. In manual mode, the input source must be explicitly configured and the DPLL will not automatically switch sources.
  • phase-offset-monitor { enable | disable } — Enable or disable phase offset monitoring between the device and its pins. When enabled, the kernel continuously measures and reports phase differences.
  • phase-offset-avg-factor FACTOR — Set the averaging factor (1-255) applied to phase offset calculations. Higher values provide smoother but slower-responding measurements.
  • frequency-monitor { enable | disable } — Enable or disable frequency monitoring on the device. When enabled, the kernel continuously measures and reports actual pin frequencies, which can be read via the measured-frequency field in pin show output.

🌈 dpll device id-get 🌈

dpll device id-get [ module-name NAME ] [ clock-id ID ] [ type TYPE ]

Retrieve the device ID based on identifying attributes. Useful for scripting when you need to find a device's numeric ID. At least one attribute should be specified to identify the device.

  • module-name NAME — Kernel module name.
  • clock-id ID — 64-bit clock identifier in decimal or hex (0x prefix).
  • type TYPE — Device type: pps or eec.

🦋 PIN COMMANDS 🦋

💖 dpll pin show 💖

dpll pin show [ id ID ] [ parent-device DEVICE_ID ] [ parent-pin PIN_ID ] [ module-name NAME ] [ clock-id ID ] [ board-label LABEL ] [ panel-label LABEL ] [ package-label LABEL ] [ type TYPE ] [ direction DIR ] [ state STATE ] [ operstate OPERSTATE ]

Display information about DPLL pins. If no arguments are specified, shows all pins in the system.

  • id ID — Show only the pin with the specified numeric identifier.
  • parent-device DEVICE_ID — Show only pins that have the specified DPLL device as a parent.
  • parent-pin PIN_ID — Show only pins that have the specified pin as a parent (mux pins).
  • module-name NAME — Show only pins provided by the specified kernel module.
  • clock-id ID — Show only pins with the specified 64-bit clock identifier.
  • board-label LABEL — Show only pins with the specified board label.
  • panel-label LABEL — Show only pins with the specified panel label.
  • package-label LABEL — Show only pins with the specified package label.
  • type TYPE — Show only pins of the specified type: mux, ext, synce-eth-port, int-oscillator, gnss.
  • direction DIR — Show only pins that have a parent-device relationship with the specified direction: input, output. When combined with parent-device, only the specified parent-device relationship is checked.
  • state STATE — Show only pins that have a parent-device relationship with the specified state: connected, disconnected, selectable. When combined with parent-device, only the specified parent-device relationship is checked.
  • operstate OPERSTATE — Show only pins that have a parent-device relationship with the specified operational state: active, standby, no-signal, qual-failed. When combined with parent-device, only the specified parent-device relationship is checked.

Output includes:

  • Pin ID
  • Module name
  • Clock ID
  • Board label (hardware label from device tree or ACPI)
  • Panel label
  • Package label
  • Pin type (mux, ext, synce-eth-port, int-oscillator, gnss)
  • Configured frequency and supported frequency ranges
  • Measured frequency in Hz (when frequency monitoring is enabled)
  • Capabilities (state-can-change, priority-can-change, direction-can-change)
  • Phase adjustment range, granularity, and current value
  • Fractional frequency offset
  • Parent device relationships (direction, priority, state, phase offset)
  • Parent pin relationships
  • Reference sync information
  • Esync frequency and pulse support (if applicable)

🍓 dpll pin set 🍓

dpll pin set id ID [ PARAMETER VALUE ] ...

Configure DPLL pin parameters. Multiple parameters can be specified in a single command.

  • id ID — Specifies which pin to configure (required).
  • frequency FREQ — Set pin frequency in Hz. The pin must support the specified frequency (check frequency-supported ranges in pin show output).
  • phase-adjust ADJUSTMENT — Set phase adjustment in picoseconds. This value fine-tunes the phase of the output signal. Negative values shift the phase backwards, positive values shift it forwards. The value must be within the phase-adjust-min and phase-adjust-max range.
  • esync-frequency FREQUENCY — Set enhanced SyncE (Synchronous Ethernet) frequency in Hz for capable pins.
  • parent-device DEVICE_ID [ direction DIR ] [ prio PRIO ] [ state STATE ] — Configure the relationship between this pin and a parent DPLL device.
    • direction { input | output } — Set the pin's direction relative to the parent device.
    • prio PRIORITY — Set priority (0-255) for this pin on the parent device.
    • state { connected | disconnected | selectable } — Set the pin's state on the parent device.
  • parent-pin PIN_ID [ state STATE ] — Configure the relationship to a parent pin.
  • reference-sync PIN_ID [ state STATE ] — Configure reference sync relationship with another pin.

🦄 dpll pin id-get 🦄

dpll pin id-get [ SELECTOR ] ...

Retrieve a pin ID based on identifying attributes.

  • module-name NAME — Filter by kernel module name.
  • clock-id ID — Filter by 64-bit clock identifier.
  • board-label LABEL — Filter by board label (hardware identifier).
  • panel-label LABEL — Filter by panel label.
  • package-label LABEL — Filter by package label.
  • type TYPE — Filter by pin type: mux, ext, synce-eth-port, int-oscillator, gnss.

💜 MONITOR COMMAND 💜

🔥 dpll monitor 🔥

dpll monitor

Monitor DPLL subsystem events in real-time. Displays notifications about:

  • Device creation, deletion, and configuration changes
  • Pin creation, deletion, and configuration changes
  • Lock status changes
  • Phase offset updates
  • Frequency changes

Events are prefixed with their type: [DEVICE_CREATE], [DEVICE_CHANGE], [DEVICE_DELETE], [PIN_CREATE], [PIN_CHANGE], [PIN_DELETE].

Press Ctrl+C to stop monitoring.

✨ EXAMPLES ✨

Okay bestie this is the part where it all clicks, like the tutorial level but make it fashion 💅 every single one of these is copy-paste ready, go wild.

🌸 Show all DPLL devices

dpll device show

🌸 Show specific device in JSON format

dpll -j device show id 0

🌸 Set device 0 to manual mode

dpll device set id 0 mode manual

🌸 Enable phase offset monitoring on device 0

dpll device set id 0 phase-offset-monitor enable

🌸 Enable frequency monitoring on device 0

dpll device set id 0 frequency-monitor enable

🌸 Show all EEC devices

dpll device show type eec

🌸 Show devices from specific module in JSON

dpll -jp device show module-name ice

🌸 Show all pins

dpll pin show

🌸 Show all GNSS pins

dpll pin show type gnss

🌸 Show GNSS pins from specific module

dpll pin show type gnss module-name ice

🌸 Show pin with pretty JSON output

dpll -jp pin show id 5

🌸 Show connected input pins on device 0

dpll pin show parent-device 0 direction input state connected

🌸 Set pin frequency to 10 MHz

dpll pin set id 0 frequency 10000000

🌸 Configure pin relationship to parent device

dpll pin set id 1 parent-device 0 prio 10 direction input state connected

🌸 Adjust phase by -1000 picoseconds

dpll pin set id 2 phase-adjust -1000

🌸 Set multiple pin parameters at once

dpll pin set id 3 frequency 10000000 phase-adjust -1000

🌸 Monitor DPLL events

dpll monitor

🌸 Monitor events in JSON format

dpll -jp monitor

🌸 Get device ID by module name

dpll device id-get module-name ice

🌸 Get pin ID by board label

dpll pin id-get board-label GNSS-1PPS

🦋 PHASE ADJUSTMENT 🦋

So phase adjustment is specified in picoseconds (1e-12 seconds), and it lets you do that fine-tuning of signal phase. This is crucial for precise time synchronization applications like 5G networks and high-frequency trading — like, the stakes are genuinely giving "one nanosecond off and everything is chaos" 😭

Important considerations, bestie, do NOT skip these:

  • Check phase-adjust-min and phase-adjust-max before setting values ⭐
  • Some hardware requires values to be multiples of phase-adjust-gran 👀
  • Negative values shift phase backwards (earlier in time)
  • Positive values shift phase forwards (later in time)
  • The kernel validates all phase adjustment requests — so it's not just vibes, it's enforced 💅

💜 CAPABILITIES 💜

Pins may have various capabilities that determine which operations are allowed. Think of it like a vibe check before you try anything:

state-can-change

The pin's state (connected/disconnected/selectable) can be modified. 🎀

priority-can-change

The pin's priority can be modified. This may apply to top-level priority or priority within parent-device relationships.

direction-can-change

The pin's direction (input/output) can be modified. 🔥

Use dpll pin show to check which capabilities a pin supports before attempting configuration changes. Fr fr, check first, then flex. ✨

🌈 EXIT STATUS 🌈

  • 0 — Success 🫶
  • 1 — Failure 💀

⭐ NOTES ⭐

  • The DPLL subsystem requires kernel support (CONFIG_DPLL=y or m)
  • Hardware support varies by device and driver
  • Some operations require specific hardware capabilities
  • Phase offset values are measured by hardware and cannot be set directly
  • Changes to device/pin configuration may affect system clock synchronization
That last one is lowkey the important one, bestie. You're not just poking a file here — you're touching things that keep the whole system's clock in line. Be gentle. 🙈

👑 SEE ALSO 👑

  • ip(8), devlink(8), ethtool(8)
  • Linux kernel documentation: Documentation/driver-api/dpll.rst
  • Netlink specification: Documentation/netlink/specs/dpll.yaml

💖 AUTHOR 💖

dpll was written by Arkadiusz Kubalewski, Vadim Fedorenko, and others.

This manual page was written by Petr Oros.

🎀 REPORTING BUGS 🎀

Report bugs to <netdev@vger.kernel.org>

And that's the whole page, bestie, you ate it 🍓 This one's from iproute2, dated 23 October 2025 — go forth and synchronize your clocks, main character 💅✨🦋

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