hw_pid: delete initial set_direction

[ykyohei]

Delete initial hwp rotation direction setting of hwp_pid agent to resolve the hwp rotation direction ambiguities.

Description

The "direction" in the hwp_pid memory register doesn't reflect the actual action of pid agent until hwp_pid.tune_freq is called. The default setting of "direction" on the agent startup lead to the ambiguity of hwp rotation direction. This PR delete the default setting.

As long as we use hwp_supervisor.pid_to_freq, we can avoid this issue.

socs/socs/agents/hwp_supervisor/agent.py

Lines 739 to 750 in 4902d3b

	if isinstance(state, ControlState.PIDToFreq):
	self.run_and_validate(clients.pid.set_direction,
	kwargs={'direction': state.direction})
	self.run_and_validate(clients.pid.declare_freq,
	kwargs={'freq': state.target_freq})
	self.run_and_validate(clients.pmx.use_ext)
	self.run_and_validate(clients.pmx.set_on)
	self.run_and_validate(clients.pid.tune_freq, timeout=60)
	self.run_and_validate(
	clients.pcu.send_command,
	kwargs={'command': 'off'}, timeout=None,
	)

However, if hwp_supervisor.pid_to_freq fails in the middle of its command sequence, we may still have a potential ambiguity in rotation direction, so maybe we should make it more robust?

Motivation and Context

https://github.com/simonsobs/chwp-discussions/discussions/24

How Has This Been Tested?

This has been tested by daq-dev for satp3. Confirmed that the restart of hwp_pid agent doen't lead to the direction ambiguity in both directions.

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.

[mhasself]

Since you've removed the .direction attribute, update the class and function docstrings to not mention it.

[BrianJKoopman]

The build error is unrelated. Working on a fix upstream.