[PATCH v3 2/5] drm/panthor: Make sure the tiler initial/max chunks are consistent

[Boris Brezillon]

It doesn't make sense to have a maximum number of chunks smaller than
the initial number of chunks attached to the context.

Fix the uAPI header to reflect the new constraint, and mention the
undocumented "initial_chunk_count > 0" constraint while at it.

v3:
- Add R-b

v2:
- Fix the check

Fixes: 9cca48fa4f89 ("drm/panthor: Add the heap logical block")
Signed-off-by: Boris Brezillon <boris.brezillon at collabora.com>
Reviewed-by: Liviu Dudau <liviu.dudau at arm.com>
Reviewed-by: Steven Price <steven.price at arm.com>
---
 drivers/gpu/drm/panthor/panthor_heap.c | 3 +++
 include/uapi/drm/panthor_drm.h         | 8 ++++++--
 2 files changed, 9 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/panthor/panthor_heap.c b/drivers/gpu/drm/panthor/panthor_heap.c
index c3c0ba744937..3be86ec383d6 100644
--- a/drivers/gpu/drm/panthor/panthor_heap.c
+++ b/drivers/gpu/drm/panthor/panthor_heap.c
@@ -281,6 +281,9 @@ int panthor_heap_create(struct panthor_heap_pool *pool,
 	if (initial_chunk_count == 0)
 		return -EINVAL;
 
+	if (initial_chunk_count > max_chunks)
+		return -EINVAL;
+
 	if (hweight32(chunk_size) != 1 ||
 	    chunk_size < SZ_256K || chunk_size > SZ_2M)
 		return -EINVAL;
diff --git a/include/uapi/drm/panthor_drm.h b/include/uapi/drm/panthor_drm.h
index dadb05ab1235..5db80a0682d5 100644
--- a/include/uapi/drm/panthor_drm.h
+++ b/include/uapi/drm/panthor_drm.h
@@ -895,13 +895,17 @@ struct drm_panthor_tiler_heap_create {
 	/** @vm_id: VM ID the tiler heap should be mapped to */
 	__u32 vm_id;
 
-	/** @initial_chunk_count: Initial number of chunks to allocate. */
+	/** @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. */
 	__u32 chunk_size;
 
-	/** @max_chunks: Maximum number of chunks that can be allocated. */
+	/**
+	 * @max_chunks: Maximum number of chunks that can be allocated.
+	 *
+	 * Must be at least @initial_chunk_count.
+	 */
 	__u32 max_chunks;
 
 	/**
-- 
2.44.0