Claude review: drm/imagination: Synchronize interrupts before suspending the GPU

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

Patch Review

**Correctness: Good**

The core fix is adding `synchronize_irq()` in `pvr_power_fw_disable()` when called from the runtime PM suspend path (`rpm_suspend=true`). This ensures any in-progress threaded IRQ handler completes before `pvr_fw_stop()` shuts down the firmware and the GPU is powered off.

The removal of `pvr_power_get()`/`pvr_power_put()` from the safety event handling in the threaded IRQ handler is correct and necessary. The commit message explains this well:

1. The threaded IRQ handler is already running because an actual hardware interrupt occurred, so the GPU must be powered on at that point.
2. The `synchronize_irq()` in the suspend path blocks the suspend callback until the threaded handler finishes, so the GPU stays powered throughout the handler's execution.
3. Keeping `pvr_power_get()` in the handler would deadlock: `synchronize_irq()` is called from the runtime PM suspend callback (which holds the PM lock), and `pvr_power_get()` → `pm_runtime_resume_and_get()` requires that same lock.

**Minor observation**: The `rpm_suspend` boolean parameter added to `pvr_power_fw_disable` is a reasonable approach, though an alternative would have been to call `synchronize_irq()` directly in `pvr_power_device_suspend()`. The chosen approach keeps the synchronization close to the firmware stop, which is arguably the right abstraction level.

**Note on the hardirq handler**: The primary hardirq handler (`pvr_device_irq_handler`) also accesses GPU registers via `pvr_fw_irq_pending()` and `pvr_device_safety_irq_pending()`. There is a small theoretical window between `synchronize_irq()` returning and `pvr_fw_stop()` completing where a new hardirq could fire and access registers. Patch 2 addresses this properly.

**Stable backport note**: The Fixes/Cc-stable tags and the below-the-fold explanation about which commit affects which kernel version are well done, making backporting easier for the stable maintainers.

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