Very Slow Laptop: SB-SMI: Mailbox transfer timeout. SB-RMI Error: 4

[jcdutton]

Device Information

System Model or SKU

[ ] Framework Laptop 16 (AMD Ryzen™ 7040 Series)
No dGPU.

BIOS VERSION

3.0.5

Windows:
N/A

Linux:
Open a terminal and run the following command
sudo dmidecode --string bios-version
03.05

DIY Edition information

Memory: Manufacture and SKU
Kingston Fury Impact: Part Number: KF556S40-32
2x making 64GB total.
Storage: Manufacture and SKU
Model Number: WD_BLACK SN850X 1000GB
Firmware Version: 620361WD
Wifi: Network controller: MEDIATEK Corp. MT7922 802.11ax PCI Express Wireless Network Adapter

Port/Peripheral information

1. USB-C card, nothing plugged in.
2. Empty
3. Empty
4. Empty
5. USB-C card, FW16 PSU plugged in.
6. USB-A card, nothing plugged in.

Standalone Operation

Are you running your mainboard as a standalone device. Is standalone mode enabled in the BIOS?

• No

Describe the bug

[33021.550100 SB-SMI: Mailbox transfer timeout]
[33021.551000 SB-RMI Error: 4]

Common symptoms: The laptop slows down to a very slow crawling page.

The above lines are repeated in the EC console log.
Looking at the EC source code, it uses this to send PMF power profile updates from the EC to the APU / CPU over an I2C/SB-SMI bus.

Possible approach to fix this:

1. FW to document what other devices are on the SB-SMI link between EC and APU. In order to determine which devices could interfere if they were misbehaving. We might then craft "recovery" algorithms to reset the misbehaving device.
2. Maybe the APU/CPU end of the link has crashed, and thus not responding to SB-SMI messages.
3. There is nothing in the SB-SMI API that allows for confirmation. I.e. the EC does a sort of fire and forget method to send the PMF update to the APU, there does not appear any way for the EC to know it if arrived corrupted or not. Maybe implementing a method for the EC to read the current setting back from the APU would provide that assurance.

Steps To Reproduce

Steps to reproduce the behavior:

1. It randomly occurs

Expected behavior

It should succeed updating the PMF profile between the EC and the APU without errors and without performance impact.

Screenshots

N/A

Operating System (please complete the following information):

• OS/Distribution: Linux/Ubuntu
• Version: 24.04
• Linux Kernel Version: uname -a 6.18.5 <- Mainline compiled kernel.

Additional context

Add any other context about the problem here.