[PATCH 19/26] drm: support more than one write fence in drm_gem_plane_helper_prepare_fb

[Christian König]

Am 25.11.21 um 16:47 schrieb Daniel Vetter:
> On Tue, Nov 23, 2021 at 03:21:04PM +0100, Christian König wrote:
>> Use dma_resv_get_singleton() here to eventually get more than one write
>> fence as single fence.
> Yeah this is nice, atomic commit helpers not supporting multiple write
> fences was really my main worry in this entire endeavour. Otherwise looks
> all rather reasonable.
>
> I'll try to find some review bandwidth, but would be really if you can
> volunteer others too (especially making sure ttm drivers set the KERNEL
> fences correctly in all cases).

Maybe I should split that up into switching over to adding the enum and 
then switching to kernel/bookkeep(previously other) for some use cases.

It would be good if I could get an rb on the trivial driver cleanups 
first. I can send those out individually if that helps.

Thanks,
Christian.

> -Daniel
>
>
>> Signed-off-by: Christian König <christian.koenig at amd.com>
>> ---
>>   drivers/gpu/drm/drm_gem_atomic_helper.c | 18 +++++++-----------
>>   1 file changed, 7 insertions(+), 11 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/drm_gem_atomic_helper.c b/drivers/gpu/drm/drm_gem_atomic_helper.c
>> index c3189afe10cb..9338ddb7edff 100644
>> --- a/drivers/gpu/drm/drm_gem_atomic_helper.c
>> +++ b/drivers/gpu/drm/drm_gem_atomic_helper.c
>> @@ -143,25 +143,21 @@
>>    */
>>   int drm_gem_plane_helper_prepare_fb(struct drm_plane *plane, struct drm_plane_state *state)
>>   {
>> -	struct dma_resv_iter cursor;
>>   	struct drm_gem_object *obj;
>>   	struct dma_fence *fence;
>> +	int ret;
>>   
>>   	if (!state->fb)
>>   		return 0;
>>   
>>   	obj = drm_gem_fb_get_obj(state->fb, 0);
>> -	dma_resv_iter_begin(&cursor, obj->resv, false);
>> -	dma_resv_for_each_fence_unlocked(&cursor, fence) {
>> -		/* TODO: Currently there should be only one write fence, so this
>> -		 * here works fine. But drm_atomic_set_fence_for_plane() should
>> -		 * be changed to be able to handle more fences in general for
>> -		 * multiple BOs per fb anyway. */
>> -		dma_fence_get(fence);
>> -		break;
>> -	}
>> -	dma_resv_iter_end(&cursor);
>> +	ret = dma_resv_get_singleton(obj->resv, false, &fence);
>> +	if (ret)
>> +		return ret;
>>   
>> +	/* TODO: drm_atomic_set_fence_for_plane() should be changed to be able
>> +	 * to handle more fences in general for multiple BOs per fb.
>> +	 */
>>   	drm_atomic_set_fence_for_plane(state, fence);
>>   	return 0;
>>   }
>> -- 
>> 2.25.1
>>