[PATCH v2 3/4] drm/panthor: Relax the constraints on the tiler chunk size

[Liviu Dudau]

On Tue, Apr 30, 2024 at 01:28:51PM +0200, Boris Brezillon wrote:
> 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.
> 
> 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 at collabora.com>

With the typo that Adrián mentioned fixed,

Reviewed-by: Liviu Dudau <liviu.dudau at arm.com>

Best regards,
Liviu

> ---
>  drivers/gpu/drm/panthor/panthor_heap.c | 8 ++++----
>  include/uapi/drm/panthor_drm.h         | 6 +++++-
>  2 files changed, 9 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/gpu/drm/panthor/panthor_heap.c b/drivers/gpu/drm/panthor/panthor_heap.c
> index 3be86ec383d6..683bb94761bc 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:2M] 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 5db80a0682d5..b8220d2e698f 100644
> --- 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;
>  
>  	/**
> -- 
> 2.44.0
> 

-- 
====================
| I would like to |
| fix the world,  |
| but they're not |
| giving me the   |
 \ source code!  /
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