drm/panthor: Fail job creation when the group is dead

Userspace can use GROUP_SUBMIT errors as a trigger to check the group
state and recreate the group if it became unusable. Make sure we
report an error when the group became unusable.

Changes in v3:
- None

Changes in v2:
- Add R-bs

Fixes: de85488 ("drm/panthor: Add the scheduler logical block")
Signed-off-by: Boris Brezillon <boris.brezillon@collabora.com>
Reviewed-by: Steven Price <steven.price@arm.com>
Reviewed-by: Liviu Dudau <liviu.dudau@arm.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20241029152912.270346-2-boris.brezillon@collabora.com

drivers/gpu/drm/panthor/panthor_sched.c

@@ -3409,6 +3409,11 @@ panthor_job_create(struct panthor_file *pfile,
 		goto err_put_job;
 	}
 
+	if (!group_can_run(job->group)) {
+		ret = -EINVAL;
+		goto err_put_job;
+	}
+
 	if (job->queue_idx >= job->group->queue_count ||
 	    !job->group->queues[job->queue_idx]) {
 		ret = -EINVAL;