1 files changed, 11 insertions, 2 deletions

diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c
index ec395a6baf9c..9da0bc5a036c 100644
--- a/drivers/spi/spi.c
+++ b/drivers/spi/spi.c
@@ -2143,8 +2143,17 @@ int spi_register_controller(struct spi_controller *ctlr)
          */
         if (ctlr->num_chipselect == 0)
                 return -EINVAL;
-        /* allocate dynamic bus number using Linux idr */
-        if ((ctlr->bus_num < 0) && ctlr->dev.of_node) {
+        if (ctlr->bus_num >= 0) {
+                /* devices with a fixed bus num must check-in with the num */
+                mutex_lock(&board_lock);
+                id = idr_alloc(&spi_master_idr, ctlr, ctlr->bus_num,
+                        ctlr->bus_num + 1, GFP_KERNEL);
+                mutex_unlock(&board_lock);
+                if (WARN(id < 0, "couldn't get idr"))
+                        return id == -ENOSPC ? -EBUSY : id;
+                ctlr->bus_num = id;
+        } else if (ctlr->dev.of_node) {
+                /* allocate dynamic bus number using Linux idr */
                 id = of_alias_get_id(ctlr->dev.of_node, "spi");
                 if (id >= 0) {
                         ctlr->bus_num = id;