Re: [Intel-gfx] [PATCH 24/28] drm: use new iterator in drm_gem_plane_helper_prepare_fb

["Christian König" <ckoenig.leichtzumerken@gmail.com>]

Am 05.10.21 um 09:53 schrieb Tvrtko Ursulin:
>
> On 01/10/2021 11:06, Christian König wrote:
>> Makes the handling a bit more complex, but avoids the use of
>> dma_resv_get_excl_unlocked().
>>
>> Signed-off-by: Christian König <christian.koenig@amd.com>
>> ---
>>   drivers/gpu/drm/drm_gem_atomic_helper.c | 13 +++++++++++--
>>   1 file changed, 11 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/drm_gem_atomic_helper.c 
>> b/drivers/gpu/drm/drm_gem_atomic_helper.c
>> index e570398abd78..21ed930042b8 100644
>> --- a/drivers/gpu/drm/drm_gem_atomic_helper.c
>> +++ b/drivers/gpu/drm/drm_gem_atomic_helper.c
>> @@ -143,6 +143,7 @@
>>    */
>>   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;
>>   @@ -150,9 +151,17 @@ int drm_gem_plane_helper_prepare_fb(struct 
>> drm_plane *plane, struct drm_plane_st
>>           return 0;
>>         obj = drm_gem_fb_get_obj(state->fb, 0);
>> -    fence = dma_resv_get_excl_unlocked(obj->resv);
>> -    drm_atomic_set_fence_for_plane(state, fence);
>> +    dma_resv_iter_begin(&cursor, obj->resv, false);
>> +    dma_resv_for_each_fence_unlocked(&cursor, fence) {
>> +        dma_fence_get(fence);
>> +        dma_resv_iter_end(&cursor);
>> +        /* TODO: We only use the first write fence here */
>
> What is the TODO? NB instead?

The drm atomic API can unfortunately handle only one fence and we can 
certainly have more than that.

>
>> + drm_atomic_set_fence_for_plane(state, fence);
>> +        return 0;
>> +    }
>> +    dma_resv_iter_end(&cursor);
>>   +    drm_atomic_set_fence_for_plane(state, NULL);
>
>     dma_resv_iter_begin(&cursor, obj->resv, false);
>     dma_resv_for_each_fence_unlocked(&cursor, fence) {
>         dma_fence_get(fence);
>         break;
>     }
>     dma_resv_iter_end(&cursor);
>
>     drm_atomic_set_fence_for_plane(state, fence);
>
> Does this work?

Yeah that should work as well.

>
> But overall I am not sure this is nicer. Is the goal to remove 
> dma_resv_get_excl_unlocked as API it just does not happen in this series?

Yes, the only user left is the i915_gem_object_last_write_engine() 
function and that one you already removed in i915.

Regards,
Christian.

>
> Regards,
>
> Tvrtko
>
>>       return 0;
>>   }
>>   EXPORT_SYMBOL_GPL(drm_gem_plane_helper_prepare_fb);
>>