how to fouce pciex4 speed is 2.5G

We install an Intel PCIex4 Ethernet, and auto running with x4 5GT/s. How can we force it running with 2.5GT/s x4 mode. Modify DTS or with special command ?

LnkCap:	Port #0, Speed 5GT/s, Width x4, ASPM L0s L1, Exit Latency L0s <4us, L1 <32us
			ClockPM- Surprise- LLActRep- BwNot- ASPMOptComp+


You can set ‘nvidia,max-speed’ DT property to 1/2/3/4 to set limit the advertisement of root port’s max supported speed capability.
But, if your intention is not to limit the maximum advertised speed by root port, but to get only the link up at a specific speed and be able to take the link to a higher speed later on, you can use ‘nvidia,init-speed’ with 1/2/3/4 to get link working at the respective speed post boot.

@nidyas Thanks for your replay.

Both either ‘nvidia,max-speed’ or ‘nvidia,init-speed’ can not be searched with “Linux_for_Tegra/sources/hardware” and “Linux_for_Tegra/sources/kernel”.

Where I can found reference code example?

Please use the rel-32.1 code base.

@WaneWWW We current use Jetpack 3.2. If we switch to rel-32.1, do we have to switch to Jetpack 4.2?
Or we just switch sources code part to rel-32.1?

You have to switch all of them.