From: Irving-CH Lin <irving-ch.lin@mediatek.com>

Enable bypass clock before MFG changing rate, to make sure
MFG reference clock available during transient.

Fixes: b66add7a74e8 ("clk: mediatek: mux: add clk notifier functions")
Signed-off-by: Irving-CH Lin <irving-ch.lin@mediatek.com>
---
 drivers/clk/mediatek/clk-mux.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/drivers/clk/mediatek/clk-mux.c b/drivers/clk/mediatek/clk-mux.c
index c5af6dc078a3..07f1f18b38bc 100644
--- a/drivers/clk/mediatek/clk-mux.c
+++ b/drivers/clk/mediatek/clk-mux.c
@@ -414,16 +414,21 @@ static int mtk_clk_mux_notifier_cb(struct notifier_block *nb,
 	struct clk_notifier_data *data = _data;
 	struct clk_hw *hw = __clk_get_hw(data->clk);
 	struct mtk_mux_nb *mux_nb = to_mtk_mux_nb(nb);
+	struct clk_hw *p_hw = clk_hw_get_parent_by_index(hw, mux_nb->bypass_index);
 	int ret = 0;
 
 	switch (event) {
 	case PRE_RATE_CHANGE:
-		mux_nb->original_index = mux_nb->ops->get_parent(hw);
-		ret = mux_nb->ops->set_parent(hw, mux_nb->bypass_index);
+		ret = clk_prepare_enable(p_hw->clk);
+		if (ret == 0) {
+			mux_nb->original_index = mux_nb->ops->get_parent(hw);
+			ret = mux_nb->ops->set_parent(hw, mux_nb->bypass_index);
+		}
 		break;
 	case POST_RATE_CHANGE:
 	case ABORT_RATE_CHANGE:
 		ret = mux_nb->ops->set_parent(hw, mux_nb->original_index);
+		clk_disable_unprepare(p_hw->clk);
 		break;
 	}
 
-- 
2.45.2