clk: mediatek: mux: Update parent at enable time

The mux clocks don't always correctly take the new parent into account
when the parent is updated while the clock is disabled. Set the update
bit when enabling the clock to force an update of the mux.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Link: https://lore.kernel.org/r/20210125170819.26130-3-laurent.pinchart@ideasonboard.com
Reviewed-by: Weiyi Lu <weiyi.lu@mediatek.com>
Signed-off-by: Stephen Boyd <sboyd@kernel.org>

Author: pinchartl

drivers/clk/mediatek/clk-mux.c

@@ -20,9 +20,33 @@ static inline struct mtk_clk_mux *to_mtk_clk_mux(struct clk_hw *hw)
 static int mtk_clk_mux_enable_setclr(struct clk_hw *hw)
 {
 	struct mtk_clk_mux *mux = to_mtk_clk_mux(hw);
+	unsigned long flags = 0;
 
-	return regmap_write(mux->regmap, mux->data->clr_ofs,
-			BIT(mux->data->gate_shift));
+	if (mux->lock)
+		spin_lock_irqsave(mux->lock, flags);
+	else
+		__acquire(mux->lock);
+
+	regmap_write(mux->regmap, mux->data->clr_ofs,
+		     BIT(mux->data->gate_shift));
+
+	/*
+	 * If the parent has been changed when the clock was disabled, it will
+	 * not be effective yet. Set the update bit to ensure the mux gets
+	 * updated.
+	 */
+	if (mux->reparent && mux->data->upd_shift >= 0) {
+		regmap_write(mux->regmap, mux->data->upd_ofs,
+			     BIT(mux->data->upd_shift));
+		mux->reparent = false;
+	}
+
+	if (mux->lock)
+		spin_unlock_irqrestore(mux->lock, flags);
+	else
+		__release(mux->lock);
+
+	return 0;
 }
 
 static void mtk_clk_mux_disable_setclr(struct clk_hw *hw)
@@ -77,9 +101,11 @@ static int mtk_clk_mux_set_parent_setclr_lock(struct clk_hw *hw, u8 index)
 		regmap_write(mux->regmap, mux->data->set_ofs,
 				index << mux->data->mux_shift);
 
-		if (mux->data->upd_shift >= 0)
+		if (mux->data->upd_shift >= 0) {
 			regmap_write(mux->regmap, mux->data->upd_ofs,
 					BIT(mux->data->upd_shift));
+			mux->reparent = true;
+		}
 	}
 
 	if (mux->lock)

drivers/clk/mediatek/clk-mux.h

@@ -14,6 +14,7 @@ struct mtk_clk_mux {
 	struct regmap *regmap;
 	const struct mtk_mux *data;
 	spinlock_t *lock;
+	bool reparent;
 };
 
 struct mtk_mux {