drm/xe: Use Xe ordered workqueue for rebind worker

A mix of the system unbound wq and Xe ordered wq was used for the
rebind, only use the Xe ordered wq. This will ensure only 1 rebind is
occuring at a time providing a somewhat clunky work around for short
comings in TTM wrt to memory contention. Once the TTM memory contention
is resolved we should be able to use a dedicated non-ordered workqueue.

Also add helper to queue rebind worker to avoid using wrong workqueue
going forward.
Reviewed-by: José Roberto de Souza <jose.souza@intel.com>
Reviewed-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Signed-off-by: Matthew Brost <matthew.brost@intel.com>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>

drivers/gpu/drm/xe/xe_preempt_fence.c

@@ -25,7 +25,7 @@ static void preempt_fence_work_func(struct work_struct *w)
 	dma_fence_signal(&pfence->base);
 	dma_fence_end_signalling(cookie);
 
-	queue_work(system_unbound_wq, &e->vm->preempt.rebind_work);
+	xe_vm_queue_rebind_worker(e->vm);
 
 	xe_engine_put(e);
 }

drivers/gpu/drm/xe/xe_vm.c

@@ -3086,8 +3086,7 @@ int xe_vm_bind_ioctl(struct drm_device *dev, void *data, struct drm_file *file)
 
 			/* Rebinds may have been blocked, give worker a kick */
 			if (xe_vm_in_compute_mode(vm))
-				queue_work(vm->xe->ordered_wq,
-					   &vm->preempt.rebind_work);
+				xe_vm_queue_rebind_worker(vm);
 		}
 
 		goto put_engine;

drivers/gpu/drm/xe/xe_vm.h

@@ -124,6 +124,12 @@ int xe_vma_userptr_pin_pages(struct xe_vma *vma);
 
 int xe_vma_userptr_check_repin(struct xe_vma *vma);
 
+static inline void xe_vm_queue_rebind_worker(struct xe_vm *vm)
+{
+	XE_WARN_ON(!xe_vm_in_compute_mode(vm));
+	queue_work(vm->xe->ordered_wq, &vm->preempt.rebind_work);
+}
+
 /*
  * XE_ONSTACK_TV is used to size the tv_onstack array that is input
  * to xe_vm_lock_dma_resv() and xe_vm_unlock_dma_resv().