clk: qcom: clk-rcg2: Fail Duty-Cycle configuration if MND divider is not enabled.

In cases when MND is not enabled (e.g. when only Half Integer Divider is
used), setting D registers makes no effect.

Fail instead of making ineffective write.

Fixes: 7f891faf ("clk: qcom: clk-rcg2: Add support for duty-cycle for RCG")
Signed-off-by: Nikita Travkin <nikita@trvn.ru>
Reviewed-by: Stephen Boyd <sboyd@kernel.org>
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Link: https://lore.kernel.org/r/20220612145955.385787-2-nikita@trvn.ru

drivers/clk/qcom/clk-rcg2.c

@@ -437,7 +437,7 @@ static int clk_rcg2_get_duty_cycle(struct clk_hw *hw, struct clk_duty *duty)
 static int clk_rcg2_set_duty_cycle(struct clk_hw *hw, struct clk_duty *duty)
 {
 	struct clk_rcg2 *rcg = to_clk_rcg2(hw);
-	u32 notn_m, n, m, d, not2d, mask, duty_per;
+	u32 notn_m, n, m, d, not2d, mask, duty_per, cfg;
 	int ret;
 
 	/* Duty-cycle cannot be modified for non-MND RCGs */
@@ -448,6 +448,11 @@ static int clk_rcg2_set_duty_cycle(struct clk_hw *hw, struct clk_duty *duty)
 
 	regmap_read(rcg->clkr.regmap, RCG_N_OFFSET(rcg), &notn_m);
 	regmap_read(rcg->clkr.regmap, RCG_M_OFFSET(rcg), &m);
+	regmap_read(rcg->clkr.regmap, RCG_CFG_OFFSET(rcg), &cfg);
+
+	/* Duty-cycle cannot be modified if MND divider is in bypass mode. */
+	if (!(cfg & CFG_MODE_MASK))
+		return -EINVAL;
 
 	n = (~(notn_m) + m) & mask;