echo spi-slave-time > /sys/class/spi_slave/spi2/slave
modprobe spi-slave-time
./spidev_test -v -D /dev/spidev0.0 -p "dummy-8B"

Logs:

root@j7200-evm:~# ./spidev_test -v -D /dev/spidev0.0 -p "dummy-8B"
spi mode: 0x0
bits per word: 8
max speed: 500000 Hz (500 kHz)
TX | 64 75 6D 6D 79 2D 38 42 __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ |dummy-8B|
RX | 00 00 00 65 00 07 82 B3 __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ |...e....|
root@j7200-evm:~# ./spidev_test -v -D /dev/spidev0.0 -p "dummy-8B"
spi mode: 0x0
bits per word: 8
max speed: 500000 Hz (500 kHz)
TX | 64 75 6D 6D 79 2D 38 42 __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ |dummy-8B|
RX | 00 00 00 66 00 04 44 F4 __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ |...f..D.|
root@j7200-evm:~# ./spidev_test -v -D /dev/spidev0.0 -p "dummy-8B"
spi mode: 0x0
bits per word: 8
max speed: 500000 Hz (500 kHz)
TX | 64 75 6D 6D 79 2D 38 42 __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ |dummy-8B|
RX | 00 00 00 67 00 00 DB 4A __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ |...g...J|

In the above test case, the MCSPI4 slave node sends the time in 64 bits format to MCU_MCSPI2 master node.