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

[Steven Price]

On 30/04/2024 14:08, Adrián Larumbe wrote:
> Hi Boris,
> 
> On 30.04.2024 13:28, 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>

Other than the typo Adrián pointed out below...

Reviewed-by: Steven Price <steven.price at arm.com>

>> ---
>>  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.
> 
> Probably a typo, but I guess this should be [128k:8M] ?
> 
>>   * @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
> 
> 
> Adrian Larumbe