Add CLK_DIVIDER_EVEN_INTEGERS flag to support divisor of 2, 4, 6, etc.
The same divisor can be done using a table, which would be big and
wasteful for a clock dividor of width 8 (256 entries).

Require increasing flags size from u8 to u16 because
CLK_DIVIDER_EVEN_INTEGERS is the eighth flag. u16 is used inside struct
clk_divider; `unsigned long` is used for function arguments.

Signed-off-by: Théo Lebrun <theo.lebrun@bootlin.com>
---
 drivers/clk/clk-divider.c    | 16 ++++++++++++----
 include/linux/clk-provider.h | 15 ++++++++++-----
 2 files changed, 22 insertions(+), 9 deletions(-)

diff --git a/drivers/clk/clk-divider.c b/drivers/clk/clk-divider.c
index a2c2b5203b0a95cf1cf651b1fb4e2c24d230d831..c1f426b8a5043cb5a1de08e1da385928ec54a2ed 100644
--- a/drivers/clk/clk-divider.c
+++ b/drivers/clk/clk-divider.c
@@ -72,6 +72,8 @@ static unsigned int _get_maxdiv(const struct clk_div_table *table, u8 width,
 		return clk_div_mask(width);
 	if (flags & CLK_DIVIDER_POWER_OF_TWO)
 		return 1 << clk_div_mask(width);
+	if (flags & CLK_DIVIDER_EVEN_INTEGERS)
+		return 2 * (clk_div_mask(width) + 1);
 	if (table)
 		return _get_table_maxdiv(table, width);
 	return clk_div_mask(width) + 1;
@@ -97,6 +99,8 @@ static unsigned int _get_div(const struct clk_div_table *table,
 		return 1 << val;
 	if (flags & CLK_DIVIDER_MAX_AT_ZERO)
 		return val ? val : clk_div_mask(width) + 1;
+	if (flags & CLK_DIVIDER_EVEN_INTEGERS)
+		return 2 * (val + 1);
 	if (table)
 		return _get_table_div(table, val);
 	return val + 1;
@@ -122,6 +126,8 @@ static unsigned int _get_val(const struct clk_div_table *table,
 		return __ffs(div);
 	if (flags & CLK_DIVIDER_MAX_AT_ZERO)
 		return (div == clk_div_mask(width) + 1) ? 0 : div;
+	if (flags & CLK_DIVIDER_EVEN_INTEGERS)
+		return (div >> 1) - 1;
 	if (table)
 		return  _get_table_val(table, div);
 	return div - 1;
@@ -538,7 +544,8 @@ struct clk_hw *__clk_hw_register_divider(struct device *dev,
 		struct device_node *np, const char *name,
 		const char *parent_name, const struct clk_hw *parent_hw,
 		const struct clk_parent_data *parent_data, unsigned long flags,
-		void __iomem *reg, u8 shift, u8 width, u8 clk_divider_flags,
+		void __iomem *reg, u8 shift, u8 width,
+		unsigned long clk_divider_flags,
 		const struct clk_div_table *table, spinlock_t *lock)
 {
 	struct clk_divider *div;
@@ -610,8 +617,8 @@ EXPORT_SYMBOL_GPL(__clk_hw_register_divider);
 struct clk *clk_register_divider_table(struct device *dev, const char *name,
 		const char *parent_name, unsigned long flags,
 		void __iomem *reg, u8 shift, u8 width,
-		u8 clk_divider_flags, const struct clk_div_table *table,
-		spinlock_t *lock)
+		unsigned long clk_divider_flags,
+		const struct clk_div_table *table, spinlock_t *lock)
 {
 	struct clk_hw *hw;
 
@@ -664,7 +671,8 @@ struct clk_hw *__devm_clk_hw_register_divider(struct device *dev,
 		struct device_node *np, const char *name,
 		const char *parent_name, const struct clk_hw *parent_hw,
 		const struct clk_parent_data *parent_data, unsigned long flags,
-		void __iomem *reg, u8 shift, u8 width, u8 clk_divider_flags,
+		void __iomem *reg, u8 shift, u8 width,
+		unsigned long clk_divider_flags,
 		const struct clk_div_table *table, spinlock_t *lock)
 {
 	struct clk_hw **ptr, *hw;
diff --git a/include/linux/clk-provider.h b/include/linux/clk-provider.h
index 7e43caabb54b901d68484b86c8349febfe12ba0f..dbe793964c24ca3ab3a7facd090dfb6ae9df7631 100644
--- a/include/linux/clk-provider.h
+++ b/include/linux/clk-provider.h
@@ -689,13 +689,15 @@ struct clk_div_table {
  * CLK_DIVIDER_BIG_ENDIAN - By default little endian register accesses are used
  *	for the divider register.  Setting this flag makes the register accesses
  *	big endian.
+ * CLK_DIVIDER_EVEN_INTEGERS - clock divisor is 2, 4, 6, 8, 10, etc.
+ *	Formula is 2 * (value read from hardware + 1).
  */
 struct clk_divider {
 	struct clk_hw	hw;
 	void __iomem	*reg;
 	u8		shift;
 	u8		width;
-	u8		flags;
+	u16		flags;
 	const struct clk_div_table	*table;
 	spinlock_t	*lock;
 };
@@ -711,6 +713,7 @@ struct clk_divider {
 #define CLK_DIVIDER_READ_ONLY		BIT(5)
 #define CLK_DIVIDER_MAX_AT_ZERO		BIT(6)
 #define CLK_DIVIDER_BIG_ENDIAN		BIT(7)
+#define CLK_DIVIDER_EVEN_INTEGERS	BIT(8)
 
 extern const struct clk_ops clk_divider_ops;
 extern const struct clk_ops clk_divider_ro_ops;
@@ -740,19 +743,21 @@ struct clk_hw *__clk_hw_register_divider(struct device *dev,
 		struct device_node *np, const char *name,
 		const char *parent_name, const struct clk_hw *parent_hw,
 		const struct clk_parent_data *parent_data, unsigned long flags,
-		void __iomem *reg, u8 shift, u8 width, u8 clk_divider_flags,
+		void __iomem *reg, u8 shift, u8 width,
+		unsigned long clk_divider_flags,
 		const struct clk_div_table *table, spinlock_t *lock);
 struct clk_hw *__devm_clk_hw_register_divider(struct device *dev,
 		struct device_node *np, const char *name,
 		const char *parent_name, const struct clk_hw *parent_hw,
 		const struct clk_parent_data *parent_data, unsigned long flags,
-		void __iomem *reg, u8 shift, u8 width, u8 clk_divider_flags,
+		void __iomem *reg, u8 shift, u8 width,
+		unsigned long clk_divider_flags,
 		const struct clk_div_table *table, spinlock_t *lock);
 struct clk *clk_register_divider_table(struct device *dev, const char *name,
 		const char *parent_name, unsigned long flags,
 		void __iomem *reg, u8 shift, u8 width,
-		u8 clk_divider_flags, const struct clk_div_table *table,
-		spinlock_t *lock);
+		unsigned long clk_divider_flags,
+		const struct clk_div_table *table, spinlock_t *lock);
 /**
  * clk_register_divider - register a divider clock with the clock framework
  * @dev: device registering this clock

-- 
2.46.2

Quoting Théo Lebrun (2024-10-07 06:49:18)
> Add CLK_DIVIDER_EVEN_INTEGERS flag to support divisor of 2, 4, 6, etc.
> The same divisor can be done using a table, which would be big and
> wasteful for a clock dividor of width 8 (256 entries).
> 
> Require increasing flags size from u8 to u16 because
> CLK_DIVIDER_EVEN_INTEGERS is the eighth flag. u16 is used inside struct
> clk_divider; `unsigned long` is used for function arguments.
> 
> Signed-off-by: Théo Lebrun <theo.lebrun@bootlin.com>
> ---

Applied to clk-next