How does the TX2 know that vdd_hdmi_5v0 is not powered on carrier board B04


Dear NV,
HDMI is not getting enabled in my personally designed carried board based on Jetson TX2.
The same software can work on NV carrier board B04,but do not work on our custom carrier board 。
Log message:[ 0.985118] tegradc 15200000.nvdisplay: dc_dp_out_hotplug_init: couldn’t get regulator vdd_hdmi_5v0
And on our custom carrier board ,HDMI_5V is direct from 5V supply。
so,we want to understand how the TX2 know vdd_hdmi_5v0 is not powered on。

HDMI 5V is enabled by a GPIO, system will be noted if this GPIO is not enabled. For your board issue, please compare to reference schematic and the checklist in OEM DG to eliminate the difference.