[igt-dev] [PATCH i-g-t 2/3] lib/intel_batchbuffer: Add support for custom engine layouts

[Karolina Drobnik]

On 24.10.2022 08:40, Zbigniew Kempczyński wrote:
> On Fri, Oct 21, 2022 at 10:54:42AM +0200, Karolina Drobnik wrote:
>> Don't assume fixed engine ids and use context configuration in
>> intel_bb to find the appropriate engine when executing the batchbuffer.
>>
>> Signed-off-by: Karolina Drobnik <karolina.drobnik at intel.com>
>> ---
>>   lib/intel_batchbuffer.c | 45 +++++++++++++++++++++++++++++++++--------
>>   1 file changed, 37 insertions(+), 8 deletions(-)
>>
>> diff --git a/lib/intel_batchbuffer.c b/lib/intel_batchbuffer.c
>> index 70d819aa..20b7e255 100644
>> --- a/lib/intel_batchbuffer.c
>> +++ b/lib/intel_batchbuffer.c
>> @@ -1490,6 +1490,31 @@ static bool aux_needs_softpin(int i915)
>>   	return intel_gen(intel_get_drm_devid(i915)) >= 12;
>>   }
>>   
>> +static bool has_ctx_cfg(struct intel_bb *ibb)
>> +{
>> +	return ibb->cfg && (ibb->cfg->num_engines > 0);
>> +}
>> +
>> +static bool find_engine(struct intel_bb *ibb, unsigned int class, uint32_t *ring)
> 
> Why not:
> 
> static uint32_t find_engine(struct intel_bb *ibb, unsigned int class)
> 
> then all logic with selecting legacy/user engine hide here in the
> implementation? Especially you're not using return value in any form.

I wanted to avoid checking for cfg in two functions, and return early if 
there is no config. But there is another problem with my approach -- we 
silently allow legacy engine id if no suitable engine was found in the 
config. Should we return -1 is such case, and check for it in 
intel_bb_flush_render() and intel_bb_flush_blit()?

All the best,
Karolina

> 
> --
> Zbigniew
> 
>> +{
>> +	intel_ctx_cfg_t *cfg;
>> +	int i;
>> +
>> +	/* Use legacy engines when there is no context config */
>> +	if (!has_ctx_cfg(ibb))
>> +		return false;
>> +
>> +	cfg = ibb->cfg;
>> +	for (i = 0; i < cfg->num_engines; i++) {
>> +		if (cfg->engines[i].engine_class == class) {
>> +			*ring = i;
>> +			return true;
>> +		}
>> +	}
>> +
>> +	return false;
>> +}
>> +
>>   /**
>>    * intel_bb_create:
>>    * @i915: drm fd
>> @@ -2790,34 +2815,38 @@ void intel_bb_flush(struct intel_bb *ibb, uint32_t ring)
>>    * intel_bb_flush_render:
>>    * @ibb: batchbuffer
>>    *
>> - * If batch is not empty emit batch buffer end, execute on render ring
>> - * and reset the batch. Context used to execute is batch context.
>> + * If batch is not empty emit batch buffer end, find the render engine id,
>> + * execute on the ring and reset the batch. Context used to execute
>> + * is batch context.
>>    */
>>   void intel_bb_flush_render(struct intel_bb *ibb)
>>   {
>> +	uint32_t ring = I915_EXEC_RENDER;
>> +
>>   	if (intel_bb_emit_flush_common(ibb) == 0)
>>   		return;
>>   
>> -	intel_bb_exec_with_ring(ibb, I915_EXEC_RENDER);
>> +	find_engine(ibb, I915_ENGINE_CLASS_RENDER, &ring);
>> +	intel_bb_exec_with_ring(ibb, ring);
>>   }
>>   
>>   /*
>>    * intel_bb_flush_blit:
>>    * @ibb: batchbuffer
>>    *
>> - * If batch is not empty emit batch buffer end, execute on default/blit ring
>> - * (depends on gen) and reset the batch.
>> + * If batch is not empty emit batch buffer end, find a suitable ring
>> + * (depending on gen and context configuration) and reset the batch.
>>    * Context used to execute is batch context.
>>    */
>>   void intel_bb_flush_blit(struct intel_bb *ibb)
>>   {
>> -	uint32_t ring = I915_EXEC_DEFAULT;
>> +	uint32_t ring;
>>   
>>   	if (intel_bb_emit_flush_common(ibb) == 0)
>>   		return;
>>   
>> -	if (HAS_BLT_RING(ibb->devid))
>> -		ring = I915_EXEC_BLT;
>> +	ring = HAS_BLT_RING(ibb->devid) ? I915_EXEC_BLT : I915_EXEC_DEFAULT;
>> +	find_engine(ibb, I915_ENGINE_CLASS_COPY, &ring);
>>   
>>   	intel_bb_exec_with_ring(ibb, ring);
>>   }
>> -- 
>> 2.25.1
>>