[Question/Bug?] Why does the sysfs current_link_speed report a different value than pp_dpm_pcie

[Quan, Evan]

[AMD Official Use Only - General]



From: amd-gfx <amd-gfx-bounces at lists.freedesktop.org> On Behalf Of Maxime Schmitt
Sent: Wednesday, April 6, 2022 1:40 AM
To: amd-gfx at lists.freedesktop.org
Subject: [Question/Bug?] Why does the sysfs current_link_speed report a different value than pp_dpm_pcie

Hello,

On my system the sysfs file "current_link_speed" is reporting "16.0 GT/s PCIe".
The GPU has support for PCIe gen 4 (AMD Radeon RX 6800 XT).
However neither the CPU (AMD Ryzen 7 1700X) nor the motherboard have support for PCIe gen 4.

The file "pp_dpm_pcie" returns the following:
0: 2.5GT/s, x1 310Mhz
1: 8.0GT/s, x16 619Mhz *
Which is correct.

Is this the expected behavior?
[Quan, Evan] "pp_dpm_pcie" is reporting the correct link speed. You can trust that.
While "current_link_speed" seems reporting the link speed the card is capable of. Not sure whether that fits design.
@Deucher, Alexander<mailto:Alexander.Deucher at amd.com> Any comments for the output of sysfs file "current_link_speed"?

BR
Evan

I am asking because I recently added AMDGPU support to a monitoring tool I maintain (nvtop) and I don't know where to get the information from.

Cheers,
Maxime

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