clk: zynqmp: Add support for clock with CLK_DIVIDER_POWER_OF_TWO flag

Existing clock divider functions is not checking for
base of divider. So, if any clock divider is power of 2
then clock rate calculation will be wrong.

Add support to calculate divider value for the clocks
with CLK_DIVIDER_POWER_OF_TWO flag.

Signed-off-by: Tejas Patel <tejas.patel@xilinx.com>
Signed-off-by: Radhey Shyam Pandey <radhey.shyam.pandey@xilinx.com>
Signed-off-by: Rajan Vaja <rajan.vaja@xilinx.com>
Link: https://lkml.kernel.org/r/1575527759-26452-7-git-send-email-rajan.vaja@xilinx.com
Signed-off-by: Stephen Boyd <sboyd@kernel.org>

drivers/clk/zynqmp/divider.c

@@ -2,7 +2,7 @@
 /*
  * Zynq UltraScale+ MPSoC Divider support
  *
- *  Copyright (C) 2016-2018 Xilinx
+ *  Copyright (C) 2016-2019 Xilinx
  *
  * Adjustable divider clock implementation
  */
@@ -45,9 +45,26 @@ struct zynqmp_clk_divider {
 };
 
 static inline int zynqmp_divider_get_val(unsigned long parent_rate,
-					 unsigned long rate)
+					 unsigned long rate, u16 flags)
 {
-	return DIV_ROUND_CLOSEST(parent_rate, rate);
+	int up, down;
+	unsigned long up_rate, down_rate;
+
+	if (flags & CLK_DIVIDER_POWER_OF_TWO) {
+		up = DIV_ROUND_UP_ULL((u64)parent_rate, rate);
+		down = DIV_ROUND_DOWN_ULL((u64)parent_rate, rate);
+
+		up = __roundup_pow_of_two(up);
+		down = __rounddown_pow_of_two(down);
+
+		up_rate = DIV_ROUND_UP_ULL((u64)parent_rate, up);
+		down_rate = DIV_ROUND_UP_ULL((u64)parent_rate, down);
+
+		return (rate - up_rate) <= (down_rate - rate) ? up : down;
+
+	} else {
+		return DIV_ROUND_CLOSEST(parent_rate, rate);
+	}
 }
 
 /**
@@ -79,6 +96,9 @@ static unsigned long zynqmp_clk_divider_recalc_rate(struct clk_hw *hw,
 	else
 		value = div >> 16;
 
+	if (divider->flags & CLK_DIVIDER_POWER_OF_TWO)
+		value = 1 << value;
+
 	if (!value) {
 		WARN(!(divider->flags & CLK_DIVIDER_ALLOW_ZERO),
 		     "%s: Zero divisor and CLK_DIVIDER_ALLOW_ZERO not set\n",
@@ -157,10 +177,13 @@ static long zynqmp_clk_divider_round_rate(struct clk_hw *hw,
 		else
 			bestdiv  = bestdiv >> 16;
 
+		if (divider->flags & CLK_DIVIDER_POWER_OF_TWO)
+			bestdiv = 1 << bestdiv;
+
 		return DIV_ROUND_UP_ULL((u64)*prate, bestdiv);
 	}
 
-	bestdiv = zynqmp_divider_get_val(*prate, rate);
+	bestdiv = zynqmp_divider_get_val(*prate, rate, divider->flags);
 
 	/*
 	 * In case of two divisors, compute best divider values and return
@@ -198,7 +221,7 @@ static int zynqmp_clk_divider_set_rate(struct clk_hw *hw, unsigned long rate,
 	int ret;
 	const struct zynqmp_eemi_ops *eemi_ops = zynqmp_pm_get_eemi_ops();
 
-	value = zynqmp_divider_get_val(parent_rate, rate);
+	value = zynqmp_divider_get_val(parent_rate, rate, divider->flags);
 	if (div_type == TYPE_DIV1) {
 		div = value & 0xFFFF;
 		div |= 0xffff << 16;
@@ -207,6 +230,9 @@ static int zynqmp_clk_divider_set_rate(struct clk_hw *hw, unsigned long rate,
 		div |= value << 16;
 	}
 
+	if (divider->flags & CLK_DIVIDER_POWER_OF_TWO)
+		div = __ffs(div);
+
 	ret = eemi_ops->clock_setdivider(clk_id, div);
 
 	if (ret)