[PATCH 2/3] drm/panthor: Make sure the tiler initial/max chunks are consistent

[Steven Price]

On 25/04/2024 08:18, Boris Brezillon wrote:
> 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.
> 
> Fixes: 9cca48fa4f89 ("drm/panthor: Add the heap logical block")
> Signed-off-by: Boris Brezillon <boris.brezillon at collabora.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 143fa35f2e74..8728c9bb76e4 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;
>  
>  	/**