Claude review: gpu: host1x: skip redundant HW state update

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

Patch Review

**Summary:** In `host1x_intr_handle_interrupt()`, skip the call to `host1x_intr_update_hw_state()` when no fences remain, since the ISR has already disabled and acknowledged the interrupt.

**Analysis:**

Looking at `process_32_syncpts()` in `intr_hw.c:14-26`:

```c
host1x_sync_writel(host, val, HOST1X_SYNC_SYNCPT_THRESH_INT_DISABLE(reg_offset));
host1x_sync_writel(host, val, HOST1X_SYNC_SYNCPT_THRESH_CPU0_INT_STATUS(reg_offset));

for_each_set_bit(id, &val, 32)
    host1x_intr_handle_interrupt(host, reg_offset * 32 + id);
```

The ISR writes to `INT_DISABLE` and `INT_STATUS` before calling `host1x_intr_handle_interrupt()`. When the fence list is empty after processing, `host1x_intr_update_hw_state()` would call `host1x_intr_disable_syncpt_intr()` (`intr_hw.c:138-145`), which does exactly the same two writes:

```c
host1x_sync_writel(host, BIT(id % 32), HOST1X_SYNC_SYNCPT_THRESH_INT_DISABLE(id / 32));
host1x_sync_writel(host, BIT(id % 32), HOST1X_SYNC_SYNCPT_THRESH_CPU0_INT_STATUS(id / 32));
```

So the optimization is correct: when the list is empty, `host1x_intr_update_hw_state` would just repeat the disable+ack that already happened. The patch skips this redundant work:

```c
if (!list_empty(&sp->fences.list))
    host1x_intr_update_hw_state(host, sp);
```

When fences remain, `host1x_intr_update_hw_state` re-programs the threshold to the next fence's value and re-enables the interrupt — this path is still taken.

**One consideration:** If a new fence is added between the ISR's disable/ack and the `list_empty` check, could we miss the re-enable? No — `host1x_intr_add_fence_locked()` calls `host1x_intr_update_hw_state()` itself, and it takes `sp->fences.lock`, which `host1x_intr_handle_interrupt` holds during this check. So there's no race.

**Verdict: Clean, correct optimization. No issues.**

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