Нашел ответ у AD (AN-1337)
Тактовую можно не выводить из HS.
Цитата
When the transmitter device (ADV7280-M, ADV7281-M, ADV7281-MA, or ADV7282-M) is programmed, the MIPI CSI-2 clock lane exits LP mode and enters HS mode.
Unless the transmitter device is manually programmed to enter LP mode or is reset, the clock lane remains in HS mode.