Re: [PATCH v6 2/6] drm: improve drm_buddy_alloc function

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On 26/12/2021 22:24, Arunpravin wrote:
- Make drm_buddy_alloc a single function to handle
   range allocation and non-range allocation demands

- Implemented a new function alloc_range() which allocates
   the requested power-of-two block comply with range limitations

- Moved order computation and memory alignment logic from
   i915 driver to drm buddy

v2:
   merged below changes to keep the build unbroken
    - drm_buddy_alloc_range() becomes obsolete and may be removed
    - enable ttm range allocation (fpfn / lpfn) support in i915 driver
    - apply enhanced drm_buddy_alloc() function to i915 driver

v3(Matthew Auld):
   - Fix alignment issues and remove unnecessary list_empty check
   - add more validation checks for input arguments
   - make alloc_range() block allocations as bottom-up
   - optimize order computation logic
   - replace uint64_t with u64, which is preferred in the kernel

v4(Matthew Auld):
   - keep drm_buddy_alloc_range() function implementation for generic
     actual range allocations
   - keep alloc_range() implementation for end bias allocations

Signed-off-by: Arunpravin <Arunpravin.PaneerSelvam@xxxxxxx>

<snip>

@@ -73,34 +83,16 @@ static int i915_ttm_buddy_man_alloc(struct ttm_resource_manager *man,
n_pages = size >> ilog2(mm->chunk_size); - do {
-		struct drm_buddy_block *block;
-		unsigned int order;
-
-		order = fls(n_pages) - 1;
-		GEM_BUG_ON(order > mm->max_order);
-		GEM_BUG_ON(order < min_order);
-
-		do {
-			mutex_lock(&bman->lock);
-			block = drm_buddy_alloc(mm, order);
-			mutex_unlock(&bman->lock);
-			if (!IS_ERR(block))
-				break;
-
-			if (order-- == min_order) {
-				err = -ENOSPC;
-				goto err_free_blocks;
-			}
-		} while (1);
-
-		n_pages -= BIT(order);
-
-		list_add_tail(&block->link, &bman_res->blocks);
-
-		if (!n_pages)
-			break;
-	} while (1);
+	mutex_lock(&bman->lock);
+	err = drm_buddy_alloc(mm, (u64)place->fpfn << PAGE_SHIFT,
+			(u64)place->lpfn << PAGE_SHIFT,

place->lpfn will currently always be zero for i915, AFAIK. I assume here we want s/place->lpfn/lpfn/?

Also something in this series is preventing i915 from loading on discrete devices, according to CI. Hopefully that is just the lpfn issue...which might explain seeing -EINVAL here[1] when allocating some vram for the firmware.

[1] https://intel-gfx-ci.01.org/tree/drm-tip/Patchwork_21904/bat-dg1-6/boot0.txt


+			(u64)n_pages << PAGE_SHIFT,
+			 min_page_size,
+			 &bman_res->blocks,
+			 bman_res->flags);
+	mutex_unlock(&bman->lock);
+	if (unlikely(err))
+		goto err_free_blocks;
*res = &bman_res->base;
  	return 0;
@@ -266,10 +258,17 @@ int i915_ttm_buddy_man_reserve(struct ttm_resource_manager *man,
  {
  	struct i915_ttm_buddy_manager *bman = to_buddy_manager(man);
  	struct drm_buddy_mm *mm = &bman->mm;
+	unsigned long flags = 0;
  	int ret;
+ flags |= DRM_BUDDY_RANGE_ALLOCATION;
+
  	mutex_lock(&bman->lock);
-	ret = drm_buddy_alloc_range(mm, &bman->reserved, start, size);
+	ret = drm_buddy_alloc(mm, start,
+			start + size,
+			size, mm->chunk_size,
+			&bman->reserved,
+			flags);
  	mutex_unlock(&bman->lock);
return ret;
diff --git a/drivers/gpu/drm/i915/i915_ttm_buddy_manager.h b/drivers/gpu/drm/i915/i915_ttm_buddy_manager.h
index fa644b512c2e..5ba490875f66 100644
--- a/drivers/gpu/drm/i915/i915_ttm_buddy_manager.h
+++ b/drivers/gpu/drm/i915/i915_ttm_buddy_manager.h
@@ -20,6 +20,7 @@ struct drm_buddy_mm;
   *
   * @base: struct ttm_resource base class we extend
   * @blocks: the list of struct i915_buddy_block for this resource/allocation
+ * @flags: DRM_BUDDY_*_ALLOCATION flags
   * @mm: the struct i915_buddy_mm for this resource
   *
   * Extends the struct ttm_resource to manage an address space allocation with
@@ -28,6 +29,7 @@ struct drm_buddy_mm;
  struct i915_ttm_buddy_resource {
  	struct ttm_resource base;
  	struct list_head blocks;
+	unsigned long flags;
  	struct drm_buddy_mm *mm;
  };
diff --git a/include/drm/drm_buddy.h b/include/drm/drm_buddy.h
index 09d73328c268..4368acaad222 100644
--- a/include/drm/drm_buddy.h
+++ b/include/drm/drm_buddy.h
@@ -13,15 +13,22 @@
#include <drm/drm_print.h> -#define range_overflows(start, size, max) ({ \
+#define check_range_overflow(start, end, size, max) ({ \
  	typeof(start) start__ = (start); \
+	typeof(end) end__ = (end);\
  	typeof(size) size__ = (size); \
  	typeof(max) max__ = (max); \
  	(void)(&start__ == &size__); \
  	(void)(&start__ == &max__); \
-	start__ >= max__ || size__ > max__ - start__; \
+	(void)(&start__ == &end__); \
+	(void)(&end__ == &size__); \
+	(void)(&end__ == &max__); \
+	start__ >= max__ || end__ > max__ || \
+	size__ > end__ - start__; \
  })
+#define DRM_BUDDY_RANGE_ALLOCATION (1 << 0)
+
  struct drm_buddy_block {
  #define DRM_BUDDY_HEADER_OFFSET GENMASK_ULL(63, 12)
  #define DRM_BUDDY_HEADER_STATE  GENMASK_ULL(11, 10)
@@ -132,12 +139,11 @@ int drm_buddy_init(struct drm_buddy_mm *mm, u64 size, u64 chunk_size);
void drm_buddy_fini(struct drm_buddy_mm *mm); -struct drm_buddy_block *
-drm_buddy_alloc(struct drm_buddy_mm *mm, unsigned int order);
-
-int drm_buddy_alloc_range(struct drm_buddy_mm *mm,
-			  struct list_head *blocks,
-			  u64 start, u64 size);
+int drm_buddy_alloc(struct drm_buddy_mm *mm,
+		    u64 start, u64 end, u64 size,
+		    u64 min_page_size,
+		    struct list_head *blocks,
+		    unsigned long flags);
void drm_buddy_free(struct drm_buddy_mm *mm, struct drm_buddy_block *block);



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