As Rafael Wysocki conceded at the beginning of a session at the 2020 Power Management and Scheduling
in the Linux Kernel summit (OSPM), the combination of the deadline scheduling class with CPU idle states
might seem a little strange. Deadline scheduling is used in realtime
settings, where introducing latency by idling the CPU tends to be frowned
upon. But there are reasons to think that these two technologies might
just be made to work together.

Source: LWN.net – [$] The deadline scheduler and CPU idle states