diff --git a/drivers/clk/rockchip/clk-mmc-phase.c b/drivers/clk/rockchip/clk-mmc-phase.c
index 3530fe33d564..3b847b7a3f06 100644
--- a/drivers/clk/rockchip/clk-mmc-phase.c
+++ b/drivers/clk/rockchip/clk-mmc-phase.c
@@ -58,6 +58,12 @@ static int rockchip_mmc_get_phase(struct clk_hw *hw)
 	u16 degrees;
 	u32 delay_num = 0;
 
+	/* See the comment for rockchip_mmc_set_phase below */
+	if (!rate) {
+		pr_err("%s: invalid clk rate\n", __func__);
+		return -EINVAL;
+	}
+
 	raw_value = readl(mmc_clock->reg) >> (mmc_clock->shift);
 
 	degrees = (raw_value & ROCKCHIP_MMC_DEGREE_MASK) * 90;
@@ -84,6 +90,25 @@ static int rockchip_mmc_set_phase(struct clk_hw *hw, int degrees)
 	u32 raw_value;
 	u32 delay;
 
+	/*
+	 * The below calculation is based on the output clock from
+	 * MMC host to the card, which expects the phase clock inherits
+	 * the clock rate from its parent, namely the output clock
+	 * provider of MMC host. However, things may go wrong if
+	 * (1) It is orphan.
+	 * (2) It is assigned to the wrong parent.
+	 *
+	 * This check help debug the case (1), which seems to be the
+	 * most likely problem we often made and explicitly makes people
+	 * harder to debug the unstable mmc tuning stuff. So hope people
+	 * to have a close look at this comment to help check out what was
+	 * happening.
+	 */
+	if (!rate) {
+		pr_err("%s: invalid clk rate\n", __func__);
+		return -EINVAL;
+	}
+
 	nineties = degrees / 90;
 	remainder = (degrees % 90);