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

1 files changed, 4 insertions, 4 deletions

diff --git a/drivers/gpu/drm/panthor/panthor_heap.c b/drivers/gpu/drm/panthor/panthor_heap.c
index 3be86ec383d6..b0fc5b9ee847 100644
--- 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);