Claude review: drm/mediatek: dsi: Store driver data before invoking mipi_dsi_host_register

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

Patch Review

**Correctness: Good**

The commit message clearly explains the bug with a full crash trace showing the call chain from `mipi_dsi_host_register` → `mtk_dsi_host_attach` → `component_add` → `mtk_dsi_bind` → `dev_get_drvdata` returning NULL. The fix moves `platform_set_drvdata(pdev, dsi)` before the `mipi_dsi_host_register()` call, which is the right thing to do.

**init_waitqueue_head move is also correct (v3 improvement):**

The `init_waitqueue_head(&dsi->irq_wait_queue)` is also moved earlier, before `platform_set_drvdata`. This is important because after `mipi_dsi_host_register` completes and `mtk_dsi_bind` runs successfully, the DSI subsystem could theoretically start operations that use the wait queue. More concretely, the IRQ handler `mtk_dsi_irq()` calls `wake_up_interruptible(&dsi->irq_wait_queue)` — so the wait queue must be initialized before `devm_request_irq()`, which is called right after `mipi_dsi_host_register()`. This was already the case in the original code (init was after request_irq — actually a latent bug!), and this patch fixes that ordering too.

**Minor observation — latent pre-existing bug also fixed:**

Looking at the original code in the drm-next tree:

```c
ret = devm_request_irq(&pdev->dev, irq_num, mtk_dsi_irq, ...);  // line 1243
...
init_waitqueue_head(&dsi->irq_wait_queue);  // line 1250
```

The original code initializes the wait queue *after* registering the IRQ handler that calls `wake_up_interruptible()` on it. This is a pre-existing race condition. This patch incidentally fixes it by moving `init_waitqueue_head` before both `mipi_dsi_host_register` and `devm_request_irq`. The commit message (v3 note) mentions this was intentional, which is good.

**No error-path concerns:** `platform_set_drvdata` and `init_waitqueue_head` don't need cleanup on failure, so moving them earlier doesn't create any resource leak issues on the error paths.

**Fixes tag:** Correctly references commit `e4732b590a77` which moved `mipi_dsi_host_register` earlier in the probe function without also moving `platform_set_drvdata` ahead of it.

**Verdict:** The patch is correct and well-motivated. No issues found.

Reviewed-by tags present: AngeloGioacchino Del Regno (Collabora) — appropriate reviewer for MediaTek DRM.

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