UMI mux test

[RiceShelley]

Description

Simplified umi_mux ready logic, and added test for umi_mux.

Screenshot of constrained random test

[Copilot]

Pull request overview

This PR simplifies umi_mux input-ready propagation logic and adds a new cocotb-based constrained-random testbench to validate mux behavior across arbitration modes and backpressure patterns.

Changes:

• Refactor umi_mux umi_in_ready generation.
• Add a new cocotb test (test_umi_mux.py) that drives multiple SUMI inputs and checks output transaction integrity.
• Add an 8-to-1 wrapper RTL module for simulation (umi_mux_8_to_1.v).

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 1 comment.

File	Description
umi/sumi/umi_mux/rtl/umi_mux.v	Updates ready-generation logic for mux inputs based on grants/out-ready.
tests/sumi/umi_mux/test_umi_mux.py	Adds constrained-random cocotb test for mux arbitration/backpressure behavior.
tests/sumi/umi_mux/rtl/umi_mux_8_to_1.v	Provides a concrete 8-input top-level wrapper to drive the parameterized mux in simulation.

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[aolofsson]

I would rename it tb_umi_mux.v and place it next to test_umi_mux.py, it's not really rtl in this context. This would be a decent pattern to follow going forward.

[RiceShelley]

I would rename it tb_umi_mux.v and place it next to test_umi_mux.py, it's not really rtl in this context. This would be a decent pattern to follow going forward.

Changed name

[aolofsson]

LGTM