Claude review: drm/rcar-du: dsi: Support DSC in the pipeline

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

Patch Review

This patch handles the pipeline topology change where the CRTC code calls `rcar_mipi_dsi_pclk_enable()` on whatever bridge is first in the chain — which is now the DSC bridge rather than the DSI bridge.

The `rcar_mipi_dsi_resolve_bridge()` approach of comparing `bridge->funcs` pointers is pragmatic. The forward declaration of `rcar_mipi_dsi_bridge_ops` is necessary and correctly placed.

```c
+static struct drm_bridge *
+rcar_mipi_dsi_resolve_bridge(struct drm_bridge *bridge)
+{
+	if (bridge->funcs != &rcar_mipi_dsi_bridge_ops)
+		bridge = bridge->next_bridge;
+
+	if (!bridge || bridge->funcs != &rcar_mipi_dsi_bridge_ops)
+		return NULL;
+
+	return bridge;
+}
```

One consideration: this function is in `rcar_mipi_dsi.c` but it needs to understand the DSC bridge's topology (specifically, that DSC's `next_bridge` points to the DSI). This works because `next_bridge` is a standard drm_bridge field, so no DSC-specific knowledge is actually needed beyond "skip one bridge if it's not ours." The comment explaining the logic is appropriate and helpful.

The `WARN_ON(!bridge)` in both callers is a reasonable choice — this situation indicates broken DT data, which shouldn't occur in a correctly configured system.

No issues.

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