clk: qcom: clk-alpha-pll: Update set_rate for Zonda PLL

The Zonda PLL has a 16 bit signed alpha and in the cases where the alpha
value is greater than 0.5, the L value needs to be adjusted accordingly.
Thus update the logic to handle the signed alpha val.

Fixes: f21b6bf ("clk: qcom: clk-alpha-pll: add support for zonda pll")
Cc: stable@vger.kernel.org
Signed-off-by: Satya Priya Kakitapalli <quic_skakitap@quicinc.com>
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Link: https://lore.kernel.org/r/20240731062916.2680823-5-quic_skakitap@quicinc.com
Signed-off-by: Bjorn Andersson <andersson@kernel.org>

Author: Satya Priya Kakitapalli

drivers/clk/qcom/clk-alpha-pll.c

@@ -41,6 +41,7 @@
 #define PLL_USER_CTL(p)		((p)->offset + (p)->regs[PLL_OFF_USER_CTL])
 # define PLL_POST_DIV_SHIFT	8
 # define PLL_POST_DIV_MASK(p)	GENMASK((p)->width - 1, 0)
+# define PLL_ALPHA_MSB		BIT(15)
 # define PLL_ALPHA_EN		BIT(24)
 # define PLL_ALPHA_MODE		BIT(25)
 # define PLL_VCO_SHIFT		20
@@ -2117,6 +2118,18 @@ static void clk_zonda_pll_disable(struct clk_hw *hw)
 	regmap_write(regmap, PLL_OPMODE(pll), 0x0);
 }
 
+static void zonda_pll_adjust_l_val(unsigned long rate, unsigned long prate, u32 *l)
+{
+	u64 remainder, quotient;
+
+	quotient = rate;
+	remainder = do_div(quotient, prate);
+	*l = quotient;
+
+	if ((remainder * 2) / prate)
+		*l = *l + 1;
+}
+
 static int clk_zonda_pll_set_rate(struct clk_hw *hw, unsigned long rate,
 				  unsigned long prate)
 {
@@ -2133,6 +2146,9 @@ static int clk_zonda_pll_set_rate(struct clk_hw *hw, unsigned long rate,
 	if (ret < 0)
 		return ret;
 
+	if (a & PLL_ALPHA_MSB)
+		zonda_pll_adjust_l_val(rate, prate, &l);
+
 	regmap_write(pll->clkr.regmap, PLL_ALPHA_VAL(pll), a);
 	regmap_write(pll->clkr.regmap, PLL_L_VAL(pll), l);