usb: xhci-mtk: 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>

diff --git a/drivers/usb/host/xhci-mtk.c b/drivers/usb/host/xhci-mtk.c
index b30806a..9066ec9 100644 (file)
--- a/drivers/usb/host/xhci-mtk.c
+++ b/drivers/usb/host/xhci-mtk.c
@@ -559,10 +559,17 @@ static int xhci_mtk_probe(struct platform_device *pdev)
                return PTR_ERR(mtk->sys_clk);
        }
 
+       /*
+        * reference clock is usually a "fixed-clock", make it optional
+        * for backward compatibility and ignore the error if it does
+        * not exist.
+        */
        mtk->ref_clk = devm_clk_get(dev, "ref_ck");
        if (IS_ERR(mtk->ref_clk)) {
-               dev_err(dev, "fail to get ref_ck\n");
-               return PTR_ERR(mtk->ref_clk);
+               if (PTR_ERR(mtk->ref_clk) == -EPROBE_DEFER)
+                       return -EPROBE_DEFER;
+
+               mtk->ref_clk = NULL;
        }
 
        mtk->lpm_support = of_property_read_bool(node, "usb3-lpm-capable");