Other Parts Discussed in Thread: TDA4VH, AM69
Tool/software:
Hello, we are attempting to enable the PCIE_SOC_REFCLK0_OUT and PCIE_SOC_REFCLK1_OUT pins on an SK-AM69 board as part of a proof-of-concept development. However, after making the device tree modifications that we thought were necessary, I am still unable to see a reference clock being generated on those pins. These pins are directly connected to test points on the SK-AM69, as follows:
| Pin | SERDES# | Test Point | Notes |
| PCIE_REFCLK1_P_OUT (AN9) | SERDES0 | TP106 | We soldered a 50Ω resistor between the test point and ground. |
| PCIE_REFCLK1_N_OUT (AN8) | SERDES0 | TP107 | We soldered a 50Ω resistor between the test point and ground. |
| PCIE_REFCLK0_P_OUT (AP5) | SERDES1 | TP104 | We soldered a 50Ω resistor between the test point and ground. |
| PCIE_REFCLK0_N_OUT (AP4) | SERDES1 | TP105 | We soldered a 50Ω resistor between the test point and ground. |
For now, let's ignore SERDES1, and focus only on SERDES0. From looking at k3-am69-sk.dts, which indirectly includes k3-j784s4-main.dtsi, it appears that SERDES0 is configured to use internal reference clock MAIN_PLL2_HSDIV4_CLKOUT (100 MHz):
serdes_wiz0: wiz@5060000 {
...
assigned-clocks = <&k3_clks 404 6>;
assigned-clock-parents = <&k3_clks 404 10>;
...
serdes0: serdes@5060000 {
...
assigned-clocks = <&serdes_wiz0 TI_WIZ_PLL0_REFCLK>,
<&serdes_wiz0 TI_WIZ_PLL1_REFCLK>,
<&serdes_wiz0 TI_WIZ_REFCLK_DIG>;
assigned-clock-parents = <&k3_clks 404 6>,
<&k3_clks 404 6>,
<&k3_clks 404 6>;
...
So now we want to source out the reference clock (MAIN_PLL2_HSDIV4_CLKOUT) from SERDES0 to TP106 and TP107. But again, looking at k3-j784s4-main.dtsi, it appears that this should already be occurring:
acspcie0_proxy_ctrl: acspcie0-ctrl@1a090 {
compatible = "ti,j784s4-acspcie-proxy-ctrl", "syscon";
reg = <0x1a090 0x4>;
};
...
pcie1_rc: pcie@2910000 {
...
ti,syscon-acspcie-proxy-ctrl = <&acspcie0_proxy_ctrl 0x1>;
...
clocks = <&k3_clks 333 0>, <&serdes0 CDNS_TORRENT_REFCLK_DRIVER>;
clock-names = "fck", "pcie_refclk";
...
However, when I connect my oscilloscope probe to TP106 or TP107, I only see a constant voltage of ~1.8 V. Any assistance that you can provide to help with debugging this would be greatly appreciated!
Best regards,
Dave
