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

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

Patch Review

**Problem analysis:** Correct. The call chain is:
`mipi_dsi_host_register` → `panel_simple_dsi_probe` → `mipi_dsi_attach` → `mtk_dsi_host_attach` → `component_add` → `mtk_dsi_bind` → `dev_get_drvdata` (returns NULL) → crash in `drm_simple_encoder_init`.

**Fix correctness:**

1. **Moving `platform_set_drvdata(pdev, dsi)` before `mipi_dsi_host_register`** — correct and necessary. This is the core fix.

2. **Moving `init_waitqueue_head(&dsi->irq_wait_queue)` before `mipi_dsi_host_register`** — also correct. Since the bind path can now execute during `mipi_dsi_host_register`, and the IRQ handler (`mtk_dsi_irq`) uses `dsi->irq_wait_queue` via `wake_up_interruptible`, the waitqueue must be initialized before any code path could potentially trigger it. While the IRQ is requested *after* `mipi_dsi_host_register`, initializing the waitqueue early is defensive and costs nothing.

3. **Error path consideration:** After this patch, if `mipi_dsi_host_register` fails, `platform_set_drvdata` will have been called but the function returns an error and the device will be torn down by devm, so no issue. If `devm_request_irq` fails, the existing cleanup (`mipi_dsi_host_unregister`) is still correct — `drvdata` being set is harmless.

**No issues found.** The Fixes tag correctly references the commit that introduced the regression. The patch is minimal and focused.

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