clk: spacemit: introduce pre-div for ddn clock

The original DDN operations applied an implicit divide-by-2, which should
not be a default behavior.

This patch removes that assumption, letting each clock define its
actual behavior explicitly.

Reviewed-by: Haylen Chu <heylenay@4d2.org>
Signed-off-by: Troy Mitchell <troy.mitchell@linux.spacemit.com>
Signed-off-by: Stephen Boyd <sboyd@kernel.org>

Author: TroyMitchell911

drivers/clk/spacemit/ccu-k1.c

@@ -136,8 +136,8 @@ CCU_GATE_DEFINE(pll1_d3_819p2, CCU_PARENT_HW(pll1_d3), MPMU_ACGR, BIT(14), 0);
 CCU_GATE_DEFINE(pll1_d2_1228p8, CCU_PARENT_HW(pll1_d2), MPMU_ACGR, BIT(16), 0);
 
 CCU_GATE_DEFINE(slow_uart, CCU_PARENT_NAME(osc), MPMU_ACGR, BIT(1), CLK_IGNORE_UNUSED);
-CCU_DDN_DEFINE(slow_uart1_14p74, pll1_d16_153p6, MPMU_SUCCR, 16, 13, 0, 13, 0);
-CCU_DDN_DEFINE(slow_uart2_48, pll1_d4_614p4, MPMU_SUCCR_1, 16, 13, 0, 13, 0);
+CCU_DDN_DEFINE(slow_uart1_14p74, pll1_d16_153p6, MPMU_SUCCR, 16, 13, 0, 13, 2, 0);
+CCU_DDN_DEFINE(slow_uart2_48, pll1_d4_614p4, MPMU_SUCCR_1, 16, 13, 0, 13, 2, 0);
 
 CCU_GATE_DEFINE(wdt_clk, CCU_PARENT_HW(pll1_d96_25p6), MPMU_WDTPCR, BIT(1), 0);
 

drivers/clk/spacemit/ccu_ddn.c

@@ -22,21 +22,21 @@
 
 #include "ccu_ddn.h"
 
-static unsigned long ccu_ddn_calc_rate(unsigned long prate,
-				       unsigned long num, unsigned long den)
+static unsigned long ccu_ddn_calc_rate(unsigned long prate, unsigned long num,
+				       unsigned long den, unsigned int pre_div)
 {
-	return prate * den / 2 / num;
+	return prate * den / pre_div / num;
 }
 
 static unsigned long ccu_ddn_calc_best_rate(struct ccu_ddn *ddn,
 					    unsigned long rate, unsigned long prate,
 					    unsigned long *num, unsigned long *den)
 {
-	rational_best_approximation(rate, prate / 2,
+	rational_best_approximation(rate, prate / ddn->pre_div,
 				    ddn->den_mask >> ddn->den_shift,
 				    ddn->num_mask >> ddn->num_shift,
 				    den, num);
-	return ccu_ddn_calc_rate(prate, *num, *den);
+	return ccu_ddn_calc_rate(prate, *num, *den, ddn->pre_div);
 }
 
 static int ccu_ddn_determine_rate(struct clk_hw *hw,
@@ -61,7 +61,7 @@ static unsigned long ccu_ddn_recalc_rate(struct clk_hw *hw, unsigned long prate)
 	num = (val & ddn->num_mask) >> ddn->num_shift;
 	den = (val & ddn->den_mask) >> ddn->den_shift;
 
-	return ccu_ddn_calc_rate(prate, num, den);
+	return ccu_ddn_calc_rate(prate, num, den, ddn->pre_div);
 }
 
 static int ccu_ddn_set_rate(struct clk_hw *hw, unsigned long rate,

drivers/clk/spacemit/ccu_ddn.h

@@ -18,13 +18,14 @@ struct ccu_ddn {
 	unsigned int num_shift;
 	unsigned int den_mask;
 	unsigned int den_shift;
+	unsigned int pre_div;
 };
 
 #define CCU_DDN_INIT(_name, _parent, _flags) \
 	CLK_HW_INIT_HW(#_name, &_parent.common.hw, &spacemit_ccu_ddn_ops, _flags)
 
 #define CCU_DDN_DEFINE(_name, _parent, _reg_ctrl, _num_shift, _num_width,	\
-		       _den_shift, _den_width, _flags)				\
+		       _den_shift, _den_width, _pre_div, _flags)		\
 static struct ccu_ddn _name = {							\
 	.common = {								\
 		.reg_ctrl	= _reg_ctrl,					\
@@ -33,7 +34,8 @@ static struct ccu_ddn _name = {							\
 	.num_mask	= GENMASK(_num_shift + _num_width - 1, _num_shift),	\
 	.num_shift	= _num_shift,						\
 	.den_mask	= GENMASK(_den_shift + _den_width - 1, _den_shift),	\
-	.den_shift	= _den_shift,					\
+	.den_shift	= _den_shift,						\
+	.pre_div	= _pre_div,						\
 }
 
 static inline struct ccu_ddn *hw_to_ccu_ddn(struct clk_hw *hw)