drm/panthor: Relax the constraints on the tiler chunk size

The field used to store the chunk size if 12 bits wide, and the encoding
is chunk_size = chunk_header.chunk_size << 12, which gives us a
theoretical [4k:8M] range. This range is further limited by
implementation constraints, and all known implementations seem to
impose a [128k:8M] range, so do the same here.

We also relax the power-of-two constraint, which doesn't seem to
exist on v10. This will allow userspace to fine-tune initial/max
tiler memory on memory-constrained devices.

v4:
- Actually fix the range in the kerneldoc

v3:
- Add R-bs
- Fix valid range in the kerneldoc

v2:
- Turn the power-of-two constraint into a page-aligned constraint to allow
  fine-tune of the initial/max heap memory size
- Fix the panthor_heap_create() kerneldoc

Fixes: 9cca48fa4f89 ("drm/panthor: Add the heap logical block")
Signed-off-by: Boris Brezillon <boris.brezillon@collabora.com>
Reviewed-by: Liviu Dudau <liviu.dudau@arm.com>
Reviewed-by: Steven Price <steven.price@arm.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240502165158.1458959-4-boris.brezillon@collabora.com

diff --git a/drivers/gpu/drm/panthor/panthor_heap.c b/drivers/gpu/drm/panthor/panthor_heap.c
index 3be86ec383d6b68fc7f9c4a742bd897537938a2f..b0fc5b9ee8479d8af3b15cb4f3ebbccf6254ada1 100644 (file)
--- a/drivers/gpu/drm/panthor/panthor_heap.c
+++ b/drivers/gpu/drm/panthor/panthor_heap.c
@@ -253,8 +253,8 @@ int panthor_heap_destroy(struct panthor_heap_pool *pool, u32 handle)
  * @pool: Pool to instantiate the heap context from.
  * @initial_chunk_count: Number of chunk allocated at initialization time.
  * Must be at least 1.
- * @chunk_size: The size of each chunk. Must be a power of two between 256k
- * and 2M.
+ * @chunk_size: The size of each chunk. Must be page-aligned and lie in the
+ * [128k:8M] range.
  * @max_chunks: Maximum number of chunks that can be allocated.
  * @target_in_flight: Maximum number of in-flight render passes.
  * @heap_ctx_gpu_va: Pointer holding the GPU address of the allocated heap
@@ -284,8 +284,8 @@ int panthor_heap_create(struct panthor_heap_pool *pool,
        if (initial_chunk_count > max_chunks)
                return -EINVAL;
 
-       if (hweight32(chunk_size) != 1 ||
-           chunk_size < SZ_256K || chunk_size > SZ_2M)
+       if (!IS_ALIGNED(chunk_size, PAGE_SIZE) ||
+           chunk_size < SZ_128K || chunk_size > SZ_8M)
                return -EINVAL;
 
        down_read(&pool->lock);

diff --git a/include/uapi/drm/panthor_drm.h b/include/uapi/drm/panthor_drm.h
index 5db80a0682d5c86c793d9a384db08b2985a1b795..b8220d2e698f538ec21a000700a2ac918766154d 100644 (file)
--- a/include/uapi/drm/panthor_drm.h
+++ b/include/uapi/drm/panthor_drm.h
@@ -898,7 +898,11 @@ struct drm_panthor_tiler_heap_create {
        /** @initial_chunk_count: Initial number of chunks to allocate. Must be at least one. */
        __u32 initial_chunk_count;
 
-       /** @chunk_size: Chunk size. Must be a power of two at least 256KB large. */
+       /**
+        * @chunk_size: Chunk size.
+        *
+        * Must be page-aligned and lie in the [128k:8M] range.
+        */
        __u32 chunk_size;
 
        /**