drm/xe/engine: add missing rpm for bind engines

Bind engines need to use the migration vm, however we don't have any rpm
for such a vm, otherwise the kernel would prevent rpm suspend-resume.
There are two issues here, first is the actual engine create which needs
to touch the lrc, but since that is in VRAM we trigger loads of missing
mem_access asserts. The second issue is when destroying the actual
engine, which requires GuC CT to deregister the context.

v2 (Rodrigo):
  - Just use ENGINE_FLAG_VM as the indicator that we need to hold an rpm
    ref. This also handles the case in xe_vm_create() where we create
    default bind engines.

Closes: https://gitlab.freedesktop.org/drm/xe/kernel/-/issues/499
Closes: https://gitlab.freedesktop.org/drm/xe/kernel/-/issues/504
Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Cc: Matthew Brost <matthew.brost@intel.com>
Signed-off-by: Matthew Auld <matthew.auld@intel.com>
Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>

drivers/gpu/drm/xe/xe_engine.c

@@ -76,6 +76,17 @@ static struct xe_engine *__xe_engine_create(struct xe_device *xe,
 	if (err)
 		goto err_lrc;
 
+	/*
+	 * Normally the user vm holds an rpm ref to keep the device
+	 * awake, and the context holds a ref for the vm, however for
+	 * some engines we use the kernels migrate vm underneath which
+	 * offers no such rpm ref. Make sure we keep a ref here, so we
+	 * can perform GuC CT actions when needed. Caller is expected to
+	 * have already grabbed the rpm ref outside any sensitive locks.
+	 */
+	if (e->flags & ENGINE_FLAG_VM)
+		drm_WARN_ON(&xe->drm, !xe_device_mem_access_get_if_ongoing(xe));
+
 	return e;
 
 err_lrc:
@@ -152,6 +163,8 @@ void xe_engine_fini(struct xe_engine *e)
 		xe_lrc_finish(e->lrc + i);
 	if (e->vm)
 		xe_vm_put(e->vm);
+	if (e->flags & ENGINE_FLAG_VM)
+		xe_device_mem_access_put(gt_to_xe(e->gt));
 
 	kfree(e);
 }
@@ -560,6 +573,9 @@ int xe_engine_create_ioctl(struct drm_device *dev, void *data,
 			if (XE_IOCTL_DBG(xe, !hwe))
 				return -EINVAL;
 
+			/* The migration vm doesn't hold rpm ref */
+			xe_device_mem_access_get(xe);
+
 			migrate_vm = xe_migrate_get_vm(gt_to_tile(gt)->migrate);
 			new = xe_engine_create(xe, migrate_vm, logical_mask,
 					       args->width, hwe,
@@ -568,6 +584,9 @@ int xe_engine_create_ioctl(struct drm_device *dev, void *data,
 					       (id ?
 					       ENGINE_FLAG_BIND_ENGINE_CHILD :
 					       0));
+
+			xe_device_mem_access_put(xe); /* now held by engine */
+
 			xe_vm_put(migrate_vm);
 			if (IS_ERR(new)) {
 				err = PTR_ERR(new);

drivers/gpu/drm/xe/xe_engine_types.h

@@ -69,6 +69,7 @@ struct xe_engine {
 #define ENGINE_FLAG_KERNEL		BIT(1)
 #define ENGINE_FLAG_PERSISTENT		BIT(2)
 #define ENGINE_FLAG_COMPUTE_MODE	BIT(3)
+/* Caller needs to hold rpm ref when creating engine with ENGINE_FLAG_VM */
 #define ENGINE_FLAG_VM			BIT(4)
 #define ENGINE_FLAG_BIND_ENGINE_CHILD	BIT(5)
 #define ENGINE_FLAG_WA			BIT(6)