After a lot of troubleshooting, I thought I would share my solution - it may be very hardware specific to me, but just in case it isn’t, here it is. If there is a more graceful solution, I would be very eager to hear it, however this was the only thing that worked for me. Apologies if this is in the wrong location, but this is the first time posting.
Symptoms: When hitting “Sleep,” the PC fans spin down for a split second, then the system immediately tries to wake up/restart. This results in “No Signal” and a total system lockup where I cannot remote SSH to find out the issue. The power button becomes unresponsive, requiring a physical power cycle via the PSU switch.
The Culprit: A two-part issue:
The motherboard (specifically the PCIe GPP bridge)
The RDNA 4 (RX 9070 XT) drivers/firmware
The Solution:
Step 1: Disable the GPP Wakeup Identify the device triggering the wake (usually GPP0 on AMD boards). To make the fix permanent on Fedora, create a tmpfile:
sudo nano /etc/tmpfiles.d/disable-gpp-wake.conf
Add the following line: w /proc/acpi/wakeup - - - - GPP0
Step 2: Update your GRUB config to use S3 (Deep) sleep and disable aggressive power features on the 9000-series that currently cause hangs.
Run the following command:
sudo grubby --update-kernel=ALL --args=“mem_sleep_default=deep amdgpu.dcdebugmask=0x10 amdgpu.ppfeaturemask=0xfffd3fff”
Result: My PC now stays asleep, and the GPU resumes correctly without locking up the system.