Rockpi 4c on Armbian 21.02.3 Buster - pcie-gen2 overlay issue

[jorgesilva]

Hi - I'm running on a Rockpi 4c on Armbian 21.02.3 Buster and it the pcie-gen2 overlay doesn't seem to do anything - I have edited the 

 

/boot/armbianEnv.txt

user_overlays=rockpi-penta

overlays=pcie-gen2

 

It makes no difference if I include the pci-gen2 overlay. 

 

lspci -vv

 LnkCap: Port #0, Speed 8GT/s, Width x2, ASPM not supported, Exit Latency L0s <256ns, L1 <8us
                        ClockPM- Surprise- LLActRep- BwNot- ASPMOptComp+
                LnkCtl: ASPM Disabled; RCB 64 bytes Disabled- CommClk-
                        ExtSynch- ClockPM- AutWidDis- BWInt- AutBWInt-
                LnkSta: Speed 5GT/s, Width x2, TrErr- Train- SlotClk- DLActive- BWMgmt- ABWMgmt

 

 

and I always get this message in dmesg :

 

8.000 Gb/s available PCIe bandwidth, limited by 5.0 GT/s PCIe x2 link at 0000:00:00.0 (capable of 15.752 Gb/s with 8.0 GT/s PCIe x2 link)

 

I am running a raid5 array and at most I seem to get just shy of at most 100MBs, - I get the same number on individual disks.

 

I

[Werner]

Providing logs with 

armbianmonitor -u

 helps with troubleshooting and significantly raises chances that issue gets addressed.

[piter75]

19 hours ago, jorgesilva said:

It makes no difference if I include the pci-gen2 overlay.

 

True, it makes no difference because the unsupported by Rockchip Gen 2 link speed was mainlined into ROCK Pi 4(a/b/c) device trees so you don't need the overlay ;-)

https://github.com/torvalds/linux/blob/master/arch/arm64/boot/dts/rockchip/rk3399-rock-pi-4.dtsi#L472

I am not sure it should be mainlined this way but it's another story.

 

19 hours ago, jorgesilva said:

8.000 Gb/s available PCIe bandwidth, limited by 5.0 GT/s PCIe x2

It confirms that you are indeed running at Gen2 speeds and have 1GiB/s physical bandwidth.

 

[jorgesilva]

Thanks for the help, I guess my question is why is it defaulting to 5GT/s and not 8GT/s - 

 

root@mininas:~# armbianmonitor -u
System diagnosis information will now be uploaded to Please post the URL in the forum where you've been asked for.

 

No url - I have run it in the past and have had a url, what am I doing wrong?

[piter75]

1 hour ago, jorgesilva said:

Thanks for the help, I guess my question is why is it defaulting to 5GT/s and not 8GT/s

RK3399 officially supports version 1.0 (2.5GT/s) and unofficially 2.0 (5GT/s).

PCIE 3.0 support is needed for 8GT/s. https://en.wikipedia.org/wiki/PCI_Express#History_and_revisions

[jorgesilva]

Hi - so everything is ok and the dmesg message is more an FYI and not  a misconfiguration i.e. it should be running at running at 8GTs. - if so thank you very much for your help.

 

8.000 Gb/s available PCIe bandwidth, limited by 5.0 GT/s PCIe x2 link at 0000:00:00.0 (capable of 15.752 Gb/s with 8.0 GT/s PCIe x2 link)