PCIe GEN3 PEX_CLK frequency

Hi,

On PCIe controllor C0 (or pcie@14180000), we have GEN3 NVMe SSD.

In device-tree, nvidia,max-speed is set to 3 for pcie@14180000.

lspci -vvv shows:

LnkCap:	Port #0, Speed 8GT/s, Width x8

LnkSta:	Speed 8GT/s, Width x2

I want to know the frequency of PEX_CLK0_N/P in this GEN3 case.

From the software, I can see:

cat /sys/kernel/debug/clk/pex0_core_0/clk_rate 

250000000

cat clk_summary | grep pex

 pex1_core_5                                                1            1   250000000   250000000          0 0  

 pex0_core_4                                                0            0   500000000   500000000          0 0  

 pex0_core_3                                                1            1    62500000    62500000          0 0  

 pex0_core_1                                                1            1    62500000    62500000          0 0  

 pex0_core_0                                                1            1   250000000   250000000          0 0  

So, it looks like the frequency of PEX_CLK0_N/P is 250 MHz?

However, according to the links below, it seems PCIe GEN3 clock frequency is 8 GHz:

I am a bit confused. In my GEN3 case, is PEX_CLK0_N/P 250 MHhz or 8 GHz? Why pex0_core_0 clock shows 250 MHz which is way lower then PCIe GEN3 standard?

Or pex0_core_0 clock is an internal reference clock, then PLL on SoC/SoM will generate 8 GHz clock on PEX_CLK0_N/P?

Thanks.