Claude review: accel/amdxdna: Return ERR_PTR on dma_alloc_noncoherent failure

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

Patch Review

**Correctness: Correct.**

The commit message clearly explains the problem: `dma_alloc_noncoherent()` returns NULL on failure, but all callers check with `IS_ERR()`. The existing code at lines 63-64 already returns `ERR_PTR(-EINVAL)` for the order check, and line 68 returns the result of `amdxdna_iommu_alloc()` which presumably also returns ERR_PTR on failure. Only the `dma_alloc_noncoherent()` path at line 70-71 was inconsistent.

Confirmed all four call sites use `IS_ERR()`:
- `aie2_message.c:399`: `if (IS_ERR(buff_addr))`
- `aie2_message.c:455`: `if (IS_ERR(addr))`
- `aie2_message.c:1206`: `if (IS_ERR(buf))`
- `aie2_error.c:358`: `if (IS_ERR(events->buf))`

Without this fix, a NULL return from `dma_alloc_noncoherent()` would pass the `IS_ERR()` check (since NULL is not in the ERR_PTR range) and lead to a NULL pointer dereference when the buffer is subsequently used (e.g., at `drm_clflush_virt_range(buff_addr, size)`).

**The fix itself:**
```c
+	vaddr = dma_alloc_noncoherent(xdna->ddev.dev, *size, dma_addr,
+				      DMA_FROM_DEVICE, GFP_KERNEL);
+	if (!vaddr)
+		return ERR_PTR(-ENOMEM);
+
+	return vaddr;
```

This is clean and follows the standard kernel pattern. `-ENOMEM` is the appropriate error code for a DMA allocation failure.

**Minor nits:**
- The Fixes tag references `ece3e8980907` which introduced the `amdxdna_iommu_alloc()` path that created the inconsistency — this is correct.
- The Signed-off-by chain (Wendy Liang as author, Lizhi Hou as submitter) is proper.

**No issues found.**

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