Re: [PATCH v7 4/4] drm/panthor: Create per queue priority workqueues

[Liviu Dudau <liviu.dudau@arm.com>]

On Thu, Oct 22, 2026 at 10:38:48AM +0100, Tvrtko Ursulin wrote:
> Split the single workqueue shared between the driver internal logic and
> DRM scheduler use into separate ones, where the DRM scheduler one is
> created per GPU priority level using the appropriate mapping to
> workqueue priorities.
> 
> Low and medium GPU priority are served by a normal workqueue,
> high is server by a WQ_HIGHPRI instance, while realtime GPU priority is
> using the newly added WQ_RTPRI flag for lowest possible latency.
> 
> These workqueues are device global and for all three we set the maximum
> concurrency to two in order to keep the GPU optimally fed with work.
> 
> Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@igalia.com>
> Cc: Boris Brezillon <boris.brezillon@collabora.com>
> Cc: Chia-I Wu <olv@google.com>
> Cc: Liviu Dudau <liviu.dudau@arm.com>
> Cc: Matthew Brost <matthew.brost@intel.com>
> Cc: Steven Price <steven.price@arm.com>
> Cc: Tejun Heo <tj@kernel.org>

Reviewed-by: Liviu Dudau <liviu.dudau@arm.com>

Best regards,
Liviu

> ---
>  drivers/gpu/drm/panthor/panthor_sched.c | 37 ++++++++++++++++++++++---
>  1 file changed, 33 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/gpu/drm/panthor/panthor_sched.c b/drivers/gpu/drm/panthor/panthor_sched.c
> index 5b34032deff8..257895e5e48b 100644
> --- a/drivers/gpu/drm/panthor/panthor_sched.c
> +++ b/drivers/gpu/drm/panthor/panthor_sched.c
> @@ -152,11 +152,18 @@ struct panthor_scheduler {
>  	 *
>  	 * Used for the scheduler tick, group update or other kind of FW
>  	 * event processing that can't be handled in the threaded interrupt
> -	 * path. Also passed to the drm_gpu_scheduler instances embedded
> -	 * in panthor_queue.
> +	 * path.
>  	 */
>  	struct workqueue_struct *wq;
>  
> +	/**
> +	 * @submit_wq: Per priority workqueues for the DRM scheduler
> +	 *
> +	 * Passed to the drm_gpu_scheduler instances embedded
> +	 * in panthor_queue based on the queue priority.
> +	 */
> +	struct workqueue_struct *submit_wq[PANTHOR_CSG_PRIORITY_COUNT];
> +
>  	/**
>  	 * @heap_alloc_wq: Workqueue used to schedule tiler_oom works.
>  	 *
> @@ -3582,8 +3589,14 @@ group_create_queue(struct panthor_group *group,
>  		goto err_free_queue;
>  	}
>  
> +	if (group->priority >= ARRAY_SIZE(group->ptdev->scheduler->submit_wq) ||
> +	    !group->ptdev->scheduler->submit_wq[group->priority]) {
> +		ret = -EINVAL;
> +		goto err_free_queue;
> +	}
> +
>  	sched_args.name = queue->name;
> -
> +	sched_args.submit_wq = group->ptdev->scheduler->submit_wq[group->priority];
>  	ret = drm_sched_init(&queue->scheduler, &sched_args);
>  	if (ret)
>  		goto err_free_queue;
> @@ -4073,6 +4086,15 @@ static void panthor_sched_fini(struct drm_device *ddev, void *res)
>  	if (!sched || !sched->csg_slot_count)
>  		return;
>  
> +	if (sched->submit_wq[PANTHOR_CSG_PRIORITY_MEDIUM])
> +		destroy_workqueue(sched->submit_wq[PANTHOR_CSG_PRIORITY_MEDIUM]);
> +
> +	if (sched->submit_wq[PANTHOR_CSG_PRIORITY_HIGH])
> +		destroy_workqueue(sched->submit_wq[PANTHOR_CSG_PRIORITY_HIGH]);
> +
> +	if (sched->submit_wq[PANTHOR_CSG_PRIORITY_RT])
> +		destroy_workqueue(sched->submit_wq[PANTHOR_CSG_PRIORITY_RT]);
> +
>  	if (sched->wq)
>  		destroy_workqueue(sched->wq);
>  
> @@ -4174,7 +4196,14 @@ int panthor_sched_init(struct panthor_device *ptdev)
>  	 */
>  	sched->heap_alloc_wq = alloc_workqueue("panthor-heap-alloc", WQ_UNBOUND, 0);
>  	sched->wq = alloc_workqueue("panthor-csf-sched", WQ_MEM_RECLAIM | WQ_UNBOUND, 0);
> -	if (!sched->wq || !sched->heap_alloc_wq) {
> +	sched->submit_wq[PANTHOR_CSG_PRIORITY_MEDIUM] = alloc_workqueue("panthor-drm", WQ_MEM_RECLAIM | WQ_UNBOUND, 2);
> +	sched->submit_wq[PANTHOR_CSG_PRIORITY_LOW] = sched->submit_wq[PANTHOR_CSG_PRIORITY_MEDIUM];
> +	sched->submit_wq[PANTHOR_CSG_PRIORITY_HIGH] = alloc_workqueue("panthor-drm-high", WQ_HIGHPRI | WQ_MEM_RECLAIM | WQ_UNBOUND, 2);
> +	sched->submit_wq[PANTHOR_CSG_PRIORITY_RT] = alloc_workqueue("panthor-drm-rt", WQ_RT | WQ_MEM_RECLAIM | WQ_UNBOUND, 2);
> +	if (!sched->wq || !sched->heap_alloc_wq ||
> +	    !sched->submit_wq[PANTHOR_CSG_PRIORITY_MEDIUM] ||
> +	    !sched->submit_wq[PANTHOR_CSG_PRIORITY_HIGH] ||
> +	    !sched->submit_wq[PANTHOR_CSG_PRIORITY_RT]) {
>  		panthor_sched_fini(&ptdev->base, sched);
>  		drm_err(&ptdev->base, "Failed to allocate the workqueues");
>  		return -ENOMEM;
> -- 
> 2.56.0
> 

-- 
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