Claude review: gpu: nova-core: add non-sec2 unload path

[Claude Code Review Bot <claude-review@example.com>]

Patch Review

**Purpose:** Split the `unload()` function so that SEC2-based architectures run the full FWSEC-SB + booter unloader sequence, while non-SEC2 architectures (Hopper/Blackwell using FSP) just wait for the GSP falcon to halt.

```rust
+        if chipset.arch().uses_sec2() {
+            /* Run FWSEC-SB to reset the GSP falcon to its pre-libos state. */
             ...existing FWSEC-SB + booter unloader code...
+        } else {
+            // GSP falcon does most of the work of resetting, so just wait for it to finish.
+            read_poll_timeout(
+                || Ok(gsp_falcon.is_riscv_active(bar)),
+                |&active| !active,
+                Delta::from_millis(10),
+                Delta::from_secs(5),
+            )
+            .inspect_err(|_| dev_err!(dev, "GSP falcon failed to halt\n"))?;
+        }
```

**Observations:**

- **Correct polling logic**: The poll waits for `is_riscv_active()` to return `false`, meaning the GSP falcon has halted. This is the inverse of the boot-time poll which waits for RISC-V to become active. The logic `|&active| !active` correctly negates the condition.

- **Timeout values**: 10ms sleep interval with 5 second timeout. The boot-time active poll uses the same values (`Delta::from_millis(10)`, `Delta::from_secs(5)`). This is consistent and seems reasonable for waiting for GSP shutdown.

- **Error logging**: Good — `.inspect_err()` provides a clear message on timeout, unlike patch 1.

- **Mixed comment styles**: Within this patch, the SEC2 path uses C-style `/* ... */` comments (preserved from the original code), while the new else branch uses Rust `//` comments. This is a very minor inconsistency, but it's understandable since the SEC2 side is just indented existing code. Not worth changing.

- **Pure indentation change on the SEC2 path**: The SEC2 side is just the existing code wrapped in an `if` block with one additional indentation level. This is clean — no behavioral changes to the existing path.

- **`read_poll_timeout` import**: This function is already imported in `boot.rs` (line 6 of the current tree shows `io::poll::read_poll_timeout`), and `Delta` is also already imported (line 10). The prerequisite unload series presumably keeps these imports intact, so no additional imports are needed for patch 3.

**Verdict:** Correct and clean. The approach of simply waiting for GSP falcon halt on non-SEC2 architectures makes hardware sense — on Hopper+, the FSP-based boot path means GSP handles its own cleanup during shutdown.

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Generated by Claude Code Patch Reviewer