Known NVRAM settings in Skiboot
A loose collection of known NVRAM settings in Skiboot. These should eventually be exposed via the Petiboot TUI.
PCIe Link Speed Cap
To cap the link speed, change the "pcie-max-link-speed" variable to the maximum generation you want to support and re-IPL the machine. For instance, to cap at PCIe Generation 3, in the petitboot command line type:
nvram -p ibm,skiboot --update-config pcie-max-link-speed=3