I have an AMD Threadripper system with an MSI X399 gaming carbon pro motherboard and a 1900X CPU. When it boots, sometimes one of my cards (Intel X550 NIC) initializes X1 link trained and sometimes it link trains at X4. I have tried this card in various other (Intel based) systems and not experienced this issue. I am uncertain if this is a Bios issue, PCIe driver issue, or something else. I am running the latest MB bios revision (V16 as of this writing). In general, it seems like cold boots come up with a X1 width for the LnkSta and warm reboots come up with X4 width for the LnkSta. This is not absolute though, as I have observed both inversions. I will attach complete outputs but here are the highlights: $ diff x550.{good,bad} 31c31 < LnkSta: Speed 8GT/s, Width x4, TrErr- Train- SlotClk+ DLActive- BWMgmt- ABWMgmt- --- > LnkSta: Speed 8GT/s, Width x1, TrErr- Train- SlotClk+ DLActive- > BWMgmt- ABWMgmt- Note that LnkCap always reports x4. $ diff lspci.all.{good,bad} [00:03.4 PCI bridge: Advanced Micro Devices, Inc. [AMD] Device 1453 (prog-if 00 [Normal decode])] 295c295 < LnkSta: Speed 8GT/s, Width x4, TrErr- Train- SlotClk+ DLActive+ BWMgmt+ ABWMgmt- --- > LnkSta: Speed 8GT/s, Width x1, TrErr- Train- SlotClk+ DLActive+ > BWMgmt+ ABWMgmt- [0b:00.0 Serial Attached SCSI controller: LSI Logic / Symbios Logic SAS3008 PCI-Express Fusion-MPT SAS-3 (rev 02)] 1414c1414 < HeaderLog: 04000001 0000200f 0b070000 b4456d62 --- > HeaderLog: 04000001 0000210f 0b070000 119631a9 [0c:00.0 Ethernet controller: Intel Corporation Ethernet Controller 10G X550T (rev 01)] 1454c1454 < LnkSta: Speed 8GT/s, Width x4, TrErr- Train- SlotClk+ DLActive- BWMgmt- ABWMgmt- --- > LnkSta: Speed 8GT/s, Width x1, TrErr- Train- SlotClk+ DLActive- > BWMgmt- ABWMgmt- [0c:00.1 Ethernet controller: Intel Corporation Ethernet Controller 10G X550T (rev 01)] 1529c1529 < LnkSta: Speed 8GT/s, Width x4, TrErr- Train- SlotClk+ DLActive- BWMgmt- ABWMgmt- --- > LnkSta: Speed 8GT/s, Width x1, TrErr- Train- SlotClk+ DLActive- > BWMgmt- ABWMgmt- This system is new and the video card that is currently in it requires the AMD DC patch set that was accepted in the 4.15-rc1 cycle. As such, I have no prior data for this configuration. I am open to installing another video card and trying older kernel versions if it would help.
Created attachment 261193 [details] Output of lspci on a boot where the device links at x1
Created attachment 261195 [details] Output of lspci on a boot where the device links at x4
Created attachment 261197 [details] Dmesg output from a x4 link boot
Created attachment 261199 [details] Dmesg output from a x1 link boot