linux-kernel - [PATCH v2 2/4] clk: spacemit: introduce pre-div for ddn clock

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Message-Id: <20250811-k1-clk-i2s-generation-v2-2-e4d3ec268b7a@linux.spacemit.com>
Date: Mon, 11 Aug 2025 22:04:28 +0800
From: Troy Mitchell <troy.mitchell@...ux.spacemit.com>
To: Michael Turquette <mturquette@...libre.com>, 
 Stephen Boyd <sboyd@...nel.org>, Rob Herring <robh@...nel.org>, 
 Krzysztof Kozlowski <krzk+dt@...nel.org>, 
 Conor Dooley <conor+dt@...nel.org>, Yixun Lan <dlan@...too.org>, 
 Alex Elder <elder@...cstar.com>, Haylen Chu <heylenay@....org>, 
 Inochi Amaoto <inochiama@...look.com>
Cc: linux-clk@...r.kernel.org, devicetree@...r.kernel.org, 
 linux-riscv@...ts.infradead.org, spacemit@...ts.linux.dev, 
 linux-kernel@...r.kernel.org, Jinmei Wei <weijinmei@...ux.spacemit.com>, 
 Troy Mitchell <troy.mitchell@...ux.spacemit.com>
Subject: [PATCH v2 2/4] 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.

Signed-off-by: Troy Mitchell <troy.mitchell@...ux.spacemit.com>
---
 drivers/clk/spacemit/ccu_ddn.c | 12 ++++++------
 drivers/clk/spacemit/ccu_ddn.h |  6 ++++--
 2 files changed, 10 insertions(+), 8 deletions(-)

diff --git a/drivers/clk/spacemit/ccu_ddn.c b/drivers/clk/spacemit/ccu_ddn.c
index be311b045698e95a688a35858a8ac1bcfbffd2c7..06d86748182bd1959cdab5c18d0a882ee25dcade 100644
--- a/drivers/clk/spacemit/ccu_ddn.c
+++ b/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 long ccu_ddn_round_rate(struct clk_hw *hw, unsigned long rate,
@@ -58,7 +58,7 @@ 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,
diff --git a/drivers/clk/spacemit/ccu_ddn.h b/drivers/clk/spacemit/ccu_ddn.h
index a52fabe77d62eba16426867a9c13481e72f025c0..4838414a8e8dc04af49d3b8d39280efedbd75616 100644
--- a/drivers/clk/spacemit/ccu_ddn.h
+++ b/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)

-- 
2.50.1