Sleeping Beauty
NetBSD on modern laptops

Jörg Sonnenberger

joerg@NetBSD.org

Jared D. McNeill

jmcneill@NetBSD.org

Outline

Motivation & Goals
The NetBSD Powermanagement Framework (PMF)
The ACPI infrastructure
Video devices
Outlook

Motivation

My laptop is my office.
Lenovo finally stopped full APM support, most other vendors earlier.
APM and SMP don't play well.
APM and AMD64 don't play well either.
Travelling around Germany drains the battery a lot.

Goals

Suspend-to-RAM of a live system
Manual disabling of unused devices
Power-saving for inactive devices
Inter-driver notification messages

PMF

Device interface
Event interface

Device interface of PMF

Device power management in layers:
- Device,
- Bus,
- Class
Suspend: Class -> Device -> Bus
Resume: Bus -> Device -> Class
Handler failed -> whole transition cancelled

The PCI/Cardbus bus handling

Suspend:
- Capture generic part of the configuration space
- Disable address decoding and bus mastering
- Transition to D3 state
- For Cardbus, optionally turn off power
Resume:
- For cardbus, turn on power
- Transition to D0 state
- Restore generic part of the configuration space
Shutdown:
- Disable address decoding and bus mastering

The network class handling

Register passes down the associated interface
Suspend calls if_stop
Resume calls if_init and if_start if IFF_UP is set
Logic to deactivate device if interface is down
Enough for most network drivers

The audio class handling

Exploits device tree to find physical device
Suspend saves current mixer settings and stops play back / recording
Resume restores mixer settings and restarts play back / recording
Optional code to suspend audio device after 30 seconds
Event handlers for volume up / down / toggle

System interface

low: pmf_device_suspend and pmf_device_resume
medium: pmf_device_recursive_suspend, pmf_device_recursive_resume, pmf_device_resume_subtree
high: pmf_system_suspend, pmf_system_resume, pmf_system_shutdown

Event interface

Send event notifications to specific devices or the whole system
Primary example: hot keys
Pure userland solution too quirky
Events are exposed via sysmon to userland
Currently implemented:
- Lid open / close
- Volume up / down / toggle
- Display on / off / brighter / darker

ACPI infrastructure

ACPI Component Architecture (ACPICA) was old, update needed
ACPI Embedded Controller (EC) needed work for that
ACPI Suspend-to-RAM support for AMD64 and SMP

ACPICA update (I)

Many bug fixes in newer release from Intel
Newer release not available from the Intel site, FreeBSD had them
Many function signature changes
New ACPICA showed locking issues in the EC driver

ACPICA update (II)

ACPI Initialisation was difficult:
- Interrupt Routing tables not parsed when ACPI System Configuration Interrupt (SCI) is set up
- Deferred Interrupt setup as workaround
Split the initialisation:
- Just initialise the system enough to read the MADT
- Parse the MADT and prepare Interrupt Routing
- Finish the initialisation

ACPI EC rewrite (I)

Used by ACPI Virtual Machine to access slow hardware
Used to inform ACPI Virtual Machine about hardware events
Very simple hardware protocol

ACPI EC rewrite (II)

ACPI EC rewrite (III)

Two one-byte ports
Query: Put reason for a SCI into the data buffer
Read: Read address from data buffer and write current value back
Write: Read address from data buffer followed by new value
Enable burst: request attention from EC for back-to-back transfer
Disable burst: release EC

ACPI EC rewrite (IV)

Before:
- Mix of polling and interrupt mode
- Interleaved code paths
- Difficult to lock correctly
After:
- Kernel thread for handling SCIs
- Read and write function as public interface
- Exclusive lock on the entry points
- State machine driven either by explicit polling or interrupts

ACPI EC rewrite (V)