RX 5500 XT: PCIe link speed stuck at Gen1 2.5GT/s by default
I'm using a RX 5500 XT card on an Asus PRIME H270-PRO motherboard, Intel i5-7500 CPU, with kernel 5.10.9 under Fedora 33. I noticed that in Linux, "lspci -vv" always showed the GPU PCIe link running at 2.5GT/s link speed and never seemed to change regardless of the application being run, while in Windows, GPU-Z shows the link running at the max supported 8GT/s speed when under graphical load.
It seems like the driver thinks that 2.5GT/s is the max allowable speed, based on the pp_dpm_pcie file:
> cd /sys/devices/pci0000:00/0000:00:01.0/0000:01:00.0/0000:02:00.0/0000:03:00.0/
> cat pp_dpm_pcie
0: 2.5GT/s, x8 81Mhz *
1: 2.5GT/s, x8 619Mhz *I'm assuming that something is going wrong with the PCIe link speed detection in the driver. Using the "amdgpu.pcie_gen_cap=0x70007" kernel command line option seems to result in the driver detecting the proper 8GT/s maximum speed.
lspci -vv output from booting without overriding the speed is attached.