[PATCH 1/2] drm/sched: add DRM_SCHED_FENCE_DONT_PIPELINE flag

[Christian König]

Gentle ping to others to get this reviewed.

Alex, this is fixing the TLB flush errors and I think we need to get it 
into -fixes ASAP.

Christian.

Am 14.10.22 um 10:15 schrieb Christian König:
> Setting this flag on a scheduler fence prevents pipelining of jobs
> depending on this fence. In other words we always insert a full CPU
> round trip before dependen jobs are pushed to the pipeline.
>
> Signed-off-by: Christian König <christian.koenig at amd.com>
> CC: stable at vger.kernel.org # 5.19+
> ---
>   drivers/gpu/drm/scheduler/sched_entity.c | 3 ++-
>   include/drm/gpu_scheduler.h              | 9 +++++++++
>   2 files changed, 11 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/scheduler/sched_entity.c b/drivers/gpu/drm/scheduler/sched_entity.c
> index 191c56064f19..43d337d8b153 100644
> --- a/drivers/gpu/drm/scheduler/sched_entity.c
> +++ b/drivers/gpu/drm/scheduler/sched_entity.c
> @@ -385,7 +385,8 @@ static bool drm_sched_entity_add_dependency_cb(struct drm_sched_entity *entity)
>   	}
>   
>   	s_fence = to_drm_sched_fence(fence);
> -	if (s_fence && s_fence->sched == sched) {
> +	if (s_fence && s_fence->sched == sched &&
> +	    !test_bit(DRM_SCHED_FENCE_DONT_PIPELINE, &fence->flags)) {
>   
>   		/*
>   		 * Fence is from the same scheduler, only need to wait for
> diff --git a/include/drm/gpu_scheduler.h b/include/drm/gpu_scheduler.h
> index 0fca8f38bee4..f01d14b231ed 100644
> --- a/include/drm/gpu_scheduler.h
> +++ b/include/drm/gpu_scheduler.h
> @@ -32,6 +32,15 @@
>   
>   #define MAX_WAIT_SCHED_ENTITY_Q_EMPTY msecs_to_jiffies(1000)
>   
> +/**
> + * DRM_SCHED_FENCE_DONT_PIPELINE - Prefent dependency pipelining
> + *
> + * Setting this flag on a scheduler fence prevents pipelining of jobs depending
> + * on this fence. In other words we always insert a full CPU round trip before
> + * dependen jobs are pushed to the hw queue.
> + */
> +#define DRM_SCHED_FENCE_DONT_PIPELINE	DMA_FENCE_FLAG_USER_BITS
> +
>   struct drm_gem_object;
>   
>   struct drm_gpu_scheduler;