[PATCH 2/2] drm/panthor: Avoid sleep locking in the internal BO size path

["Adrián Larumbe" <adrian.larumbe@collabora.com>]

A previous commit dealt with a similar situation, whereby upon enabling
some mutex debug features, a warning about sleep muteces being used in a
/proc file read atomic context was being triggered.

Because in this case replacing the heap mutex with a spinlock isn't
feasible, the fdinfo handler no longer traverses the list of heaps for
every single VM associated with an open DRM file. Instad, when a new heap
chunk is allocated, its size is accumulated into a VM-wide tally, which
also makes the atomic context code path somewhat faster.

Signed-off-by: Adrián Larumbe <adrian.larumbe@collabora.com>
Fixes: 3e2c8c718567 ("drm/panthor: Expose size of driver internal BO's over fdinfo")
---
 drivers/gpu/drm/panthor/panthor_heap.c | 38 ++++++++------------------
 drivers/gpu/drm/panthor/panthor_heap.h |  2 --
 drivers/gpu/drm/panthor/panthor_mmu.c  | 18 +++++++-----
 drivers/gpu/drm/panthor/panthor_mmu.h  |  1 +
 4 files changed, 23 insertions(+), 36 deletions(-)

diff --git a/drivers/gpu/drm/panthor/panthor_heap.c b/drivers/gpu/drm/panthor/panthor_heap.c
index db0285ce5812..686f209f5b09 100644
--- a/drivers/gpu/drm/panthor/panthor_heap.c
+++ b/drivers/gpu/drm/panthor/panthor_heap.c
@@ -127,6 +127,8 @@ static void panthor_free_heap_chunk(struct panthor_vm *vm,
 	heap->chunk_count--;
 	mutex_unlock(&heap->lock);
 
+	panthor_vm_heaps_accumulate(vm, -heap->chunk_size);
+
 	panthor_kernel_bo_destroy(chunk->bo);
 	kfree(chunk);
 }
@@ -180,6 +182,8 @@ static int panthor_alloc_heap_chunk(struct panthor_device *ptdev,
 	heap->chunk_count++;
 	mutex_unlock(&heap->lock);
 
+	panthor_vm_heaps_accumulate(vm, heap->chunk_size);
+
 	return 0;
 
 err_destroy_bo:
@@ -389,6 +393,7 @@ int panthor_heap_return_chunk(struct panthor_heap_pool *pool,
 			removed = chunk;
 			list_del(&chunk->node);
 			heap->chunk_count--;
+			panthor_vm_heaps_accumulate(chunk->bo->vm, -heap->chunk_size);
 			break;
 		}
 	}
@@ -560,6 +565,8 @@ panthor_heap_pool_create(struct panthor_device *ptdev, struct panthor_vm *vm)
 	if (ret)
 		goto err_destroy_pool;
 
+	panthor_vm_heaps_accumulate(vm, pool->gpu_contexts->obj->size);
+
 	return pool;
 
 err_destroy_pool:
@@ -594,8 +601,11 @@ void panthor_heap_pool_destroy(struct panthor_heap_pool *pool)
 	xa_for_each(&pool->xa, i, heap)
 		drm_WARN_ON(&pool->ptdev->base, panthor_heap_destroy_locked(pool, i));
 
-	if (!IS_ERR_OR_NULL(pool->gpu_contexts))
+	if (!IS_ERR_OR_NULL(pool->gpu_contexts)) {
+		panthor_vm_heaps_accumulate(pool->gpu_contexts->vm,
+					    -pool->gpu_contexts->obj->size);
 		panthor_kernel_bo_destroy(pool->gpu_contexts);
+	}
 
 	/* Reflects the fact the pool has been destroyed. */
 	pool->vm = NULL;
@@ -603,29 +613,3 @@ void panthor_heap_pool_destroy(struct panthor_heap_pool *pool)
 
 	panthor_heap_pool_put(pool);
 }
-
-/**
- * panthor_heap_pool_size() - Calculate size of all chunks across all heaps in a pool
- * @pool: Pool whose total chunk size to calculate.
- *
- * This function adds the size of all heap chunks across all heaps in the
- * argument pool. It also adds the size of the gpu contexts kernel bo.
- * It is meant to be used by fdinfo for displaying the size of internal
- * driver BO's that aren't exposed to userspace through a GEM handle.
- *
- */
-size_t panthor_heap_pool_size(struct panthor_heap_pool *pool)
-{
-	struct panthor_heap *heap;
-	unsigned long i;
-	size_t size = 0;
-
-	down_read(&pool->lock);
-	xa_for_each(&pool->xa, i, heap)
-		size += heap->chunk_size * heap->chunk_count;
-	up_read(&pool->lock);
-
-	size += pool->gpu_contexts->obj->size;
-
-	return size;
-}
diff --git a/drivers/gpu/drm/panthor/panthor_heap.h b/drivers/gpu/drm/panthor/panthor_heap.h
index e3358d4e8edb..25a5f2bba445 100644
--- a/drivers/gpu/drm/panthor/panthor_heap.h
+++ b/drivers/gpu/drm/panthor/panthor_heap.h
@@ -27,8 +27,6 @@ struct panthor_heap_pool *
 panthor_heap_pool_get(struct panthor_heap_pool *pool);
 void panthor_heap_pool_put(struct panthor_heap_pool *pool);
 
-size_t panthor_heap_pool_size(struct panthor_heap_pool *pool);
-
 int panthor_heap_grow(struct panthor_heap_pool *pool,
 		      u64 heap_gpu_va,
 		      u32 renderpasses_in_flight,
diff --git a/drivers/gpu/drm/panthor/panthor_mmu.c b/drivers/gpu/drm/panthor/panthor_mmu.c
index 0a4e352b5505..aaad1a560805 100644
--- a/drivers/gpu/drm/panthor/panthor_mmu.c
+++ b/drivers/gpu/drm/panthor/panthor_mmu.c
@@ -345,6 +345,10 @@ struct panthor_vm {
 
 		/** @heaps.lock: Lock used to protect access to @pool. */
 		struct mutex lock;
+
+		/** @heaps.size: Size of all chunks across all heaps in the pool. */
+		ssize_t size;
+
 	} heaps;
 
 	/** @node: Used to insert the VM in the panthor_mmu::vm::list. */
@@ -1539,6 +1543,7 @@ static void panthor_vm_destroy(struct panthor_vm *vm)
 	mutex_lock(&vm->heaps.lock);
 	panthor_heap_pool_destroy(vm->heaps.pool);
 	vm->heaps.pool = NULL;
+	vm->heaps.size = 0;
 	mutex_unlock(&vm->heaps.lock);
 
 	drm_WARN_ON(&vm->ptdev->base,
@@ -1963,13 +1968,7 @@ void panthor_vm_heaps_sizes(struct panthor_file *pfile, struct drm_memory_stats
 
 	xa_lock(&pfile->vms->xa);
 	xa_for_each(&pfile->vms->xa, i, vm) {
-		size_t size = 0;
-
-		mutex_lock(&vm->heaps.lock);
-		if (vm->heaps.pool)
-			size = panthor_heap_pool_size(vm->heaps.pool);
-		mutex_unlock(&vm->heaps.lock);
-
+		size_t size = vm->heaps.size;
 		stats->resident += size;
 		if (vm->as.id >= 0)
 			stats->active += size;
@@ -1977,6 +1976,11 @@ void panthor_vm_heaps_sizes(struct panthor_file *pfile, struct drm_memory_stats
 	xa_unlock(&pfile->vms->xa);
 }
 
+void panthor_vm_heaps_accumulate(struct panthor_vm *vm, ssize_t acc)
+{
+	vm->heaps.size += acc;
+}
+
 static u64 mair_to_memattr(u64 mair, bool coherent)
 {
 	u64 memattr = 0;
diff --git a/drivers/gpu/drm/panthor/panthor_mmu.h b/drivers/gpu/drm/panthor/panthor_mmu.h
index fc274637114e..b6686896f8ef 100644
--- a/drivers/gpu/drm/panthor/panthor_mmu.h
+++ b/drivers/gpu/drm/panthor/panthor_mmu.h
@@ -39,6 +39,7 @@ struct panthor_heap_pool *
 panthor_vm_get_heap_pool(struct panthor_vm *vm, bool create);
 
 void panthor_vm_heaps_sizes(struct panthor_file *pfile, struct drm_memory_stats *stats);
+void panthor_vm_heaps_accumulate(struct panthor_vm *vm, ssize_t acc);
 
 struct panthor_vm *panthor_vm_get(struct panthor_vm *vm);
 void panthor_vm_put(struct panthor_vm *vm);
-- 
2.47.1