Custom board HDMI hotplug detect(HPD) did't work

[YasirHu]

Hi community:
I have a custom board using hdmi, and HPD did not work which mesns when I pull down HPD, there is nothing happened, the ubuntu GUI still work fine.
I used a DP to HDMI cable for Orin devkit, and when I pull down HPD, the monitor has no GUI. When I pull up HPD, GUI get back.
My L4T is R34.1.1, and I have done some steps below:

1. followed https://docs.nvidia.com/jetson/archives/r34.1/DeveloperGuide/text/SD/Kernel/DisplayConfigurationAndBringUp.html#for-jetson-agx-orin-enabling-hdmi-on-custom-carrier-boards to enable HDMI
2. add os_gpio_hotplug_a in tegra234-p3701-0000-p3737-0000.dts:

display@13800000 {
                os_gpio_hotplug_a = <&tegra_main_gpio TEGRA234_MAIN_GPIO(M, 0) GPIO_ACTIVE_HIGH>;
                status = "okay";
        };

And below is my hardware design:

I use Maxim Integrated MAX96751 as HDMI connector, and HPD is output by MAX96751.A_VDDIO_751 is 1.8v.