Hi,
The NVMe is not detected when serial console logs are disabled, I mean by setting both Coreboot log_level=Error (or less) and FSP PcdFspDebugPrintErrorLevel=NoDebug. Looks like the enumeration fails then further on the device is not listed in the UEFI FW (same issue shown in either CorebootPayloadPkg or UefiPayloadPkg). When Linux boots the device appears normally.
The problem is fixed by adding a small delay inside dev_enumerate() - a 20ms delay at the very beginning of the function is enough. I'm wondering if there is a better solution for this, the device is already defined in the devicetree.cb (set as on). Maybe coreboot is too fast and the NVMe is still booting up - or the PCIe link is still training, not sure. Coreboot doesn't retry if the device is not detected right away?
Kind regards, Sumo