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Subject[PATCH RESEND V3 2/9] clk: fractional-divider: add CLK_FRAC_DIVIDER_ZERO_BASED flag support
Date
Adding CLK_FRAC_DIVIDER_ZERO_BASED flag to indicate the numerator and
denominator value in register are start from 0.

This can be used to support frac dividers like below:
Divider output clock = Divider input clock x [(frac +1) / (div +1)]
where frac/div in register is:
000b - Divide by 1.
001b - Divide by 2.
010b - Divide by 3.

Cc: Stephen Boyd <sboyd@codeaurora.org>
Cc: Michael Turquette <mturquette@baylibre.com>
Signed-off-by: Dong Aisheng <aisheng.dong@nxp.com>

---
ChangeLog:
v2->v3:
* no changes
v1->v2:
* improve comments suggested by Stephen
---
drivers/clk/clk-fractional-divider.c | 10 ++++++++++
include/linux/clk-provider.h | 8 ++++++++
2 files changed, 18 insertions(+)

diff --git a/drivers/clk/clk-fractional-divider.c b/drivers/clk/clk-fractional-divider.c
index fdf625f..7ccde6b 100644
--- a/drivers/clk/clk-fractional-divider.c
+++ b/drivers/clk/clk-fractional-divider.c
@@ -40,6 +40,11 @@ static unsigned long clk_fd_recalc_rate(struct clk_hw *hw,
m = (val & fd->mmask) >> fd->mshift;
n = (val & fd->nmask) >> fd->nshift;

+ if (fd->flags & CLK_FRAC_DIVIDER_ZERO_BASED) {
+ m++;
+ n++;
+ }
+
if (!n || !m)
return parent_rate;

@@ -103,6 +108,11 @@ static int clk_fd_set_rate(struct clk_hw *hw, unsigned long rate,
GENMASK(fd->mwidth - 1, 0), GENMASK(fd->nwidth - 1, 0),
&m, &n);

+ if (fd->flags & CLK_FRAC_DIVIDER_ZERO_BASED) {
+ m--;
+ n--;
+ }
+
if (fd->lock)
spin_lock_irqsave(fd->lock, flags);
else
diff --git a/include/linux/clk-provider.h b/include/linux/clk-provider.h
index 68ccd36..cb55b67 100644
--- a/include/linux/clk-provider.h
+++ b/include/linux/clk-provider.h
@@ -566,6 +566,12 @@ void clk_hw_unregister_fixed_factor(struct clk_hw *hw);
* @lock: register lock
*
* Clock with adjustable fractional divider affecting its output frequency.
+ *
+ * Flags:
+ * CLK_FRAC_DIVIDER_ZERO_BASED - by default the numerator and denominator
+ * is the value read from the register. If CLK_FRAC_DIVIDER_ZERO_BASED
+ * is set then the numerator and denominator are both the value read
+ * plus one.
*/
struct clk_fractional_divider {
struct clk_hw hw;
@@ -585,6 +591,8 @@ struct clk_fractional_divider {

#define to_clk_fd(_hw) container_of(_hw, struct clk_fractional_divider, hw)

+#define CLK_FRAC_DIVIDER_ZERO_BASED BIT(0)
+
extern const struct clk_ops clk_fractional_divider_ops;
struct clk *clk_register_fractional_divider(struct device *dev,
const char *name, const char *parent_name, unsigned long flags,
--
2.7.4
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