Tune Off

configname: CONFIG_PCIE_BUS_TUNE_OFF

PCI Express hierarchy optimization setting
└─>PCI support
└─>Tune Off
In linux kernel since version 5.1 (release Date: 2019-05-05)  
Use the BIOS defaults; don't touch MPS at all. This is the same
as booting with 'pci=pcie_bus_tune_off'.

depends
CONFIG_PCI