Claude review: drm/bridge: imx93-mipi-dsi: Fix mode validation

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

Patch Review

**Logic change — correct:**

The key change from checking the last bridge to iterating any bridge after the DSI bridge is correct. The commit message clearly explains the scenario: the last bridge is typically a display connector bridge without ops, while an intermediate bridge (e.g., an HDMI bridge chip) is the one that sets `DRM_BRIDGE_OP_DETECT | DRM_BRIDGE_OP_EDID`.

**Refcount handling — correct:**

The helper `imx93_dsi_get_next_bridge_in_chain()` correctly drops the reference on the current bridge before returning the next one:

```c
static inline struct drm_bridge *
imx93_dsi_get_next_bridge_in_chain(struct drm_bridge *bridge)
{
	struct drm_bridge *next = drm_bridge_get_next_bridge(bridge);

	drm_bridge_put(bridge);

	return next;
}
```

Both early-exit paths inside the loop body correctly call `drm_bridge_put(bridge)` before returning/breaking:

```c
			drm_bridge_put(bridge);
			return MODE_NOCLOCK;
		}

		drm_bridge_put(bridge);
		break;
```

If no bridge matches and the loop exhausts, the last iteration's `imx93_dsi_get_next_bridge_in_chain()` returns NULL after putting the last bridge — also correct.

**Locking — correctly handled:**

The call chain is: `drm_bridge_chain_mode_valid()` → `drm_for_each_bridge_in_chain_from()` (acquires `bridge_chain_mutex`) → `dw_mipi_dsi_bridge_mode_valid()` → `imx93_dsi_mode_valid()` → `imx93_dsi_validate_mode()`. Since `bridge_chain_mutex` is already held, using `drm_for_each_bridge_in_chain_from()` here would deadlock (as discovered in v2). The manual iteration via `drm_bridge_get_next_bridge()` is safe because that function doesn't take the mutex — it just traverses the list, which is protected by the caller's lock.

**Minor observation (non-blocking):**

`dw_mipi_dsi_get_bridge()` returns `&dsi->bridge` — a raw pointer to an embedded struct without incrementing the refcount. The `drm_bridge_get_next_bridge()` API contract states "The caller is responsible of having a reference to @bridge via drm_bridge_get() or equivalent." In practice this is safe because the embedded bridge outlives the call, and the pre-existing code already relied on this same pattern. But a `drm_bridge_get(dmd_bridge)` / `drm_bridge_put(dmd_bridge)` pair would be more strictly correct. This is pre-existing and not introduced by this patch, so not a concern for this fix.

**Reviewed-by: appropriate.** The patch has Frank Li's R-b tag and the fix is straightforward and correct.

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