Nonfunctional UART2 on TX2i R32.3.1

I am trying to use UART2 connected to pins A15, A16, B15, B16 on a TX2i.
The module is installed on custom carrier board, but this connection follows the devboard design.
No changes to serial port DTB entries.

Devices constructed as expected:
/dev/ttyTHS1 /dev/ttyTHS2 /dev/ttyTHS3

The dmesg output is
iommu: Adding device 3100000.serial to group 15
iommu: Adding device 3110000.serial to group 16
iommu: Adding device c280000.serial to group 17
iommu: Adding device 3130000.serial to group 18
3100000.serial: ttyS0 at MMIO 0x3100000 (irq = 36, base_baud = 25500000) is a Tegra
3110000.serial: ttyTHS1 at MMIO 0x3110000 (irq = 37, base_baud = 0) is a TEGRA_UART
c280000.serial: ttyTHS2 at MMIO 0xc280000 (irq = 38, base_baud = 0) is a TEGRA_UART
serial-tegra 3130000.serial: RX in PIO mode
3130000.serial: ttyTHS3 at MMIO 0x3130000 (irq = 39, base_baud = 0) is a TEGRA_UART

Unclear why only one port indicates: RX in PIO mode

stty for each port returns
speed 9600 baud; line = 0;
-brkint -imaxbel

I have read the OEM and adaptation guides; and all the entries in the forum that have any relevance.

No data flows in or out of the port.

Pleas download
and check UART application (app/uart-app.c)