Claude review: drm/ttm: Support 52-bit PAs in ttm_place

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

Patch Review

**Already superseded in drm-next.** The fields have been changed to `uint64_t`, which is the correct fix.

**Type choice concern:** Even if this weren't superseded, `unsigned long` would be the wrong type here. On 32-bit kernels, `unsigned long` is 32 bits — identical to `unsigned` — so the patch would silently provide no benefit on those platforms. The `uint64_t` already in drm-next avoids this problem.

```c
-	unsigned	fpfn;
-	unsigned	lpfn;
+	unsigned long	fpfn;
+	unsigned long	lpfn;
```

**Missing downstream widening:** Note that even with the TTM-level fix (whether this patch or the drm-next version), `struct amdgpu_mem_partition_info` in `amdgpu_gmc.h` still uses `uint32_t` for its `fpfn`/`lpfn`:

```c
struct amdgpu_mem_partition_info {
	union {
		struct {
			uint32_t fpfn;
			uint32_t lpfn;
		} range;
```

These values feed directly into `places[c].fpfn` at `amdgpu_object.c:123`:

```c
places[c].fpfn = adev->gmc.mem_partitions[mem_id].range.fpfn;
...
places[c].lpfn = adev->gmc.mem_partitions[mem_id].range.lpfn + 1;
```

If the goal is truly 52-bit PA support for AMD GPUs, this downstream struct also needs widening. A follow-up patch addressing `amdgpu_mem_partition_info` would be needed to make the full path consistent.

**No callers updated:** The patch changes the struct definition but doesn't update any callers that may be using `unsigned` or `uint32_t` local variables to hold these values. A grep shows ~31 files touch `fpfn`/`lpfn` across multiple drivers (amdgpu, xe, i915, nouveau, radeon, vmwgfx, qxl, etc.). While many assign literal 0 (safe), some do arithmetic that could be affected by the type change. The patch should have audited these call sites, or at minimum mentioned them in the commit message.

**Verdict:** This patch is redundant with drm-next and uses an inferior type. If the submitter needs 52-bit PA support, they should rebase onto drm-next (which already has the `uint64_t` fix) and submit follow-up patches to widen the AMD-specific structures like `amdgpu_mem_partition_info`.

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