Getting Started With ACPI

# Fixing Embedded Controllers: Manual

TO-DO:

  • Finish Edge cases and sample SSDT edits

# Finding the ACPI path

To find the ACPI pathing, you have 2 methods:

# DSDT

Finding the ACPI pathing is quite easy actually, first open your decompiled DSDT you got from Dumping the DSDT and Decompiling and Compiling with either MaciASL(if in macOS) or any other text editor if in Windows or Linux(VSCode has an ACPI extension (opens new window) that can also help).

Next, search for PNP0C09. You should get something similar:

From the above example we see 2 main things:

  • Name of our embedded controller
    • In this case being EC0
  • Pathing of our embedded controller
    • PC00.LPC0

But now we get into edge case territory, what fun!

The main ones to check for are:

If none of the above apply to you, you're ready for the next section:

# DeviceManager

If you already have Windows installed on this machine, finding the EC pathing is fairly easy.

Start by opening up Device Manager in Windows and looking for a device named Embedded Controller. Once found, click on it and select the BIOS device Name entry. You should get something like this:

From the above, we can see that our pathing is SB.PC00.LPC0.EC0

Now with the pathing, you can head here: Edits to the sample SSDT

# Edits to the sample SSDT

Now that we have our ACPI path, lets grab our SSDT and get to work:

Now when opening this SSDT, you'll notice a few things. Mainly:

  • Some code is commented out
    • This is code for disabling our EC
    • Laptops users SHOULD NOT uncomment this
  • There's a new EC called Device (EC)
    • DO NOT RENAME THIS, this will be the EC we give to macOS

Before:

External (_SB_.PCI0.LPCB, DeviceObj) <- Rename this

Scope (_SB.PCI0.LPCB) <- Rename this

Following the example pathing we found, the SSDT should look something like this:

After:

External (_SB_.PC00.LPC0, DeviceObj) <- Renamed

Scope (_SB.PC00.LPC0) <- Renamed

# Edge Cases

# Multiple PNP0C09's show up

When multiple PNP0C09 show up, we need to next check for the following properties:

  • _HID (Hardware ID)
  • _CRS (Current Resource Settings)
  • _GPE (General Purpose Events)

What these signify is whether this PNP0C09 device is real or not, as per the ACPI spec (opens new window). So one's matching the above criteria are the one's we want to disable.

# No PNP0C09 show up

When this happens, you'll only need to create a "dummy" EC for macOS.

Try searching for any devices named: "LPCB", "LPC0", "LPC", "SBRG", "PX40". If you have any of these, try using the LPC pathing of each of those device in place of the Embedded Controller's pathing.

Note that DO NOT uncomment the EC disabling code as there are no devices that are considered "EC" in your machine.

# PNP0C09 already named EC

Congrats! No need to create an SSDT-EC! However you will still want USBX if you're Skylake or newer.

Prebuilt can be grabbed here: SSDT-USBX.aml (opens new window)

# PNP0C09 already has a _STA method

This is the equivalent of not having an EC as we can't control it with our SSDT-EC, instead we'll need to create a "dummy" EC for macOS. You'll still want to find the PCI and LPC pathing for this device. So follow the guide as if you were creating a laptop SSDT-EC/USBX.

Example of an EC with STA already:

Credit to rottenpants466

# Compiling the SSDT

With the SSDT done, you're now ready to compile the SSDT!

# Wrapping up

Once you're done making your SSDT, either head to the next page to finish the rest of the SSDTs or head here if you're ready to wrap up:

⟵ DMAR Table (VT-d) ⟶