How to disable ASPM for a certain PCIe device?

You can also try setting this kernel parameter

pcie_aspm.policy=performance

instead of telling the kernel to ignore it.

To check the current policy run

cat /sys/module/pcie_aspm/parameters/policy

Also don’t forget run sudo reinstall-kernels if you are using dracut befor rebooting so the kernel paramaters actually get applied.

To check if any PCI devices have ASPM enabled you can run

sudo lspci -vvv | grep "ASPM .*abled"