usb: mtu3: make the reference clock optional

Make the reference clock optional for DTS backward compatibility
and ignore the error if it does not exist.

Signed-off-by: Chunfeng Yun <chunfeng.yun@mediatek.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 9 insertions, 2 deletions

diff --git a/drivers/usb/mtu3/mtu3_plat.c b/drivers/usb/mtu3/mtu3_plat.c
index 19a345d6687d..c3125da66bab 100644
--- a/drivers/usb/mtu3/mtu3_plat.c
+++ b/drivers/usb/mtu3/mtu3_plat.c
@@ -225,10 +225,17 @@ static int get_ssusb_rscs(struct platform_device *pdev, struct ssusb_mtk *ssusb)
                 return PTR_ERR(ssusb->sys_clk);
         }
 
+        /*
+         * reference clock is usually a "fixed-clock", make it optional
+         * for backward compatibility and ignore the error if it does
+         * not exist.
+         */
         ssusb->ref_clk = devm_clk_get(dev, "ref_ck");
         if (IS_ERR(ssusb->ref_clk)) {
-                dev_err(dev, "failed to get ref clock\n");
-                return PTR_ERR(ssusb->ref_clk);
+                if (PTR_ERR(ssusb->ref_clk) == -EPROBE_DEFER)
+                        return -EPROBE_DEFER;
+
+                ssusb->ref_clk = NULL;
         }
 
         ssusb->num_phys = of_count_phandle_with_args(node,