Re: [PATCH v3 2/3] drm/amdgpu: Reset the clear flag in buddy during resume

[Arunpravin Paneer Selvam]

On 7/10/2025 7:50 PM, Matthew Auld wrote:

On 10/07/2025 08:14, Arunpravin Paneer Selvam wrote:

On 7/8/2025 2:30 PM, Matthew Auld wrote:

On 08/07/2025 07:54, Arunpravin Paneer Selvam wrote:

- Added a handler in DRM buddy manager to reset the cleared
   flag for the blocks in the freelist.

- This is necessary because, upon resuming, the VRAM becomes
   cluttered with BIOS data, yet the VRAM backend manager
   believes that everything has been cleared.

v2:

   - Add lock before accessing drm_buddy_clear_reset_blocks()(Matthew Auld)

   - Force merge the two dirty blocks.(Matthew Auld)
   - Add a new unit test case for this issue.(Matthew Auld)

   - Having this function being able to flip the state either way would be

     good. (Matthew Brost)

v3(Matthew Auld):
   - Do merge step first to avoid the use of extra reset flag.

Signed-off-by: Arunpravin Paneer Selvam <arunpravin.paneersel...@amd.com>

Suggested-by: Christian König <christian.koe...@amd.com>
Cc: sta...@vger.kernel.org
Fixes: a68c7eaa7a8f ("drm/amdgpu: Enable clear page functionality")
Closes: https://gitlab.freedesktop.org/drm/amd/-/issues/3812

Reviewed-by: Matthew Auld <matthew.a...@intel.com>

Is this RB also for the unit test case (patch 3).

Feel free to apply my r-b there also.

Thanks!

Thanks,

Arun.

---
  drivers/gpu/drm/amd/amdgpu/amdgpu_device.c   |  2 +
  drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.h      |  1 +
  drivers/gpu/drm/amd/amdgpu/amdgpu_vram_mgr.c | 17 ++++++++

  drivers/gpu/drm/drm_buddy.c                  | 43 ++++++++++++++++++++

  include/drm/drm_buddy.h                      |  2 +
  5 files changed, 65 insertions(+)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c b/drivers/ gpu/drm/amd/amdgpu/amdgpu_device.c

index a59f194e3360..b89e46f29b51 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c

@@ -5193,6 +5193,8 @@ int amdgpu_device_resume(struct drm_device *dev, bool notify_clients)

          dev->dev->power.disable_depth--;
  #endif
      }
+
+    amdgpu_vram_mgr_clear_reset_blocks(adev);
      adev->in_suspend = false;
        if (amdgpu_acpi_smart_shift_update(dev, AMDGPU_SS_DEV_D0))

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.h b/drivers/gpu/ drm/amd/amdgpu/amdgpu_ttm.h

index 208b7d1d8a27..450e4bf093b7 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.h
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.h

@@ -154,6 +154,7 @@ int amdgpu_vram_mgr_reserve_range(struct amdgpu_vram_mgr *mgr,

                    uint64_t start, uint64_t size);
  int amdgpu_vram_mgr_query_page_status(struct amdgpu_vram_mgr *mgr,
                        uint64_t start);
+void amdgpu_vram_mgr_clear_reset_blocks(struct amdgpu_device *adev);
    bool amdgpu_res_cpu_visible(struct amdgpu_device *adev,
                  struct ttm_resource *res);

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_vram_mgr.c b/drivers/ gpu/drm/amd/amdgpu/amdgpu_vram_mgr.c

index abdc52b0895a..07c936e90d8e 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_vram_mgr.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_vram_mgr.c

@@ -782,6 +782,23 @@ uint64_t amdgpu_vram_mgr_vis_usage(struct amdgpu_vram_mgr *mgr)

      return atomic64_read(&mgr->vis_usage);
  }
  +/**
+ * amdgpu_vram_mgr_clear_reset_blocks - reset clear blocks
+ *
+ * @adev: amdgpu device pointer
+ *
+ * Reset the cleared drm buddy blocks.
+ */
+void amdgpu_vram_mgr_clear_reset_blocks(struct amdgpu_device *adev)
+{
+    struct amdgpu_vram_mgr *mgr = &adev->mman.vram_mgr;
+    struct drm_buddy *mm = &mgr->mm;
+
+    mutex_lock(&mgr->lock);
+    drm_buddy_reset_clear(mm, false);
+    mutex_unlock(&mgr->lock);
+}
+
  /**

   * amdgpu_vram_mgr_intersects - test each drm buddy block for intersection

   *
diff --git a/drivers/gpu/drm/drm_buddy.c b/drivers/gpu/drm/drm_buddy.c
index a1e652b7631d..a94061f373de 100644
--- a/drivers/gpu/drm/drm_buddy.c
+++ b/drivers/gpu/drm/drm_buddy.c
@@ -405,6 +405,49 @@ drm_get_buddy(struct drm_buddy_block *block)
  }
  EXPORT_SYMBOL(drm_get_buddy);
  +/**
+ * drm_buddy_reset_clear - reset blocks clear state
+ *
+ * @mm: DRM buddy manager
+ * @is_clear: blocks clear state
+ *
+ * Reset the clear state based on @is_clear value for each block
+ * in the freelist.
+ */
+void drm_buddy_reset_clear(struct drm_buddy *mm, bool is_clear)
+{
+    u64 root_size, size, start;
+    unsigned int order;
+    int i;
+
+    size = mm->size;
+    for (i = 0; i < mm->n_roots; ++i) {
+        order = ilog2(size) - ilog2(mm->chunk_size);
+        start = drm_buddy_block_offset(mm->roots[i]);
+        __force_merge(mm, start, start + size, order);
+
+        root_size = mm->chunk_size << order;
+        size -= root_size;
+    }
+
+    for (i = 0; i <= mm->max_order; ++i) {
+        struct drm_buddy_block *block;
+
+        list_for_each_entry_reverse(block, &mm->free_list[i], link) {
+            if (is_clear != drm_buddy_block_is_clear(block)) {
+                if (is_clear) {
+                    mark_cleared(block);

+                    mm->clear_avail += drm_buddy_block_size(mm, block);

+                } else {
+                    clear_reset(block);

+                    mm->clear_avail -= drm_buddy_block_size(mm, block);

+                }
+            }
+        }
+    }
+}
+EXPORT_SYMBOL(drm_buddy_reset_clear);
+
  /**
   * drm_buddy_free_block - free a block
   *
diff --git a/include/drm/drm_buddy.h b/include/drm/drm_buddy.h
index 9689a7c5dd36..513837632b7d 100644
--- a/include/drm/drm_buddy.h
+++ b/include/drm/drm_buddy.h
@@ -160,6 +160,8 @@ int drm_buddy_block_trim(struct drm_buddy *mm,
               u64 new_size,
               struct list_head *blocks);
  +void drm_buddy_reset_clear(struct drm_buddy *mm, bool is_clear);
+

  void drm_buddy_free_block(struct drm_buddy *mm, struct drm_buddy_block *block);

    void drm_buddy_free_list(struct drm_buddy *mm,