Enabling AML Debugging
The aml-debugger.txt, the instruction for enabling AML runtime debugger, is available at Documentation/acpi/ in Linux kernel source code. In short, two things are required for AML runtime debugging
- Enable AML debugging (CONFIG_ACPI_DEBUGGER=y & CONFIG_ACPI_DEBUGGER_USER=m) when compiling Linux kernel
- Compile an utility, acpidbg from Linux kernel (I uploaded a copy here)
Running AML Debugging
Executing acpidbg on Ubuntu 18.04 (x64) is straight-forward
and "help" shows a list supported commands
acpidbg is particularly handy when one needs to evaluate any ACPI AML objects during runtime - especially ones that change under different conditions. This may be explained by some examples below:
Example 1 - To determine AC power status in runtime.
- Find _PSR objects
- Evaluate _PSR when AC is disconnected
- Evaluate _PSR when AC is connected.
acpidbg also works with complex objects such as packages.
Example 2 - To determine battery information and status.
- Find _BIF and _BST objects
- Evaluate _BIF and _BST objects (note _BST changes dynamically).
acpidbg can decode bit fields and save time on counting bits. Try to run acpidbg to evaluate any _PLD objects and you will see what I mean :).