[PATCH v2 03/18] CLK: Add fractional divider clock support from Linux kernel

[Andrey Panov]

Signed-off-by: Andrey Panov <rockford at yandex.ru>
---
 drivers/clk/Makefile                 |   3 +-
 drivers/clk/clk-fractional-divider.c | 152 +++++++++++++++++++++++++++++++++++
 include/linux/clk.h                  |   9 +++
 3 files changed, 163 insertions(+), 1 deletion(-)
 create mode 100644 drivers/clk/clk-fractional-divider.c

diff --git a/drivers/clk/Makefile b/drivers/clk/Makefile
index 9df98c8..47ed7b1 100644
--- a/drivers/clk/Makefile
+++ b/drivers/clk/Makefile
@@ -1,5 +1,6 @@
 obj-$(CONFIG_COMMON_CLK)	+= clk.o clk-fixed.o clk-divider.o clk-fixed-factor.o \
-				clk-mux.o clk-gate.o clk-composite.o
+				clk-mux.o clk-gate.o clk-composite.o \
+				clk-fractional-divider.o
 obj-$(CONFIG_CLKDEV_LOOKUP)	+= clkdev.o
 
 obj-$(CONFIG_ARCH_MVEBU)	+= mvebu/
diff --git a/drivers/clk/clk-fractional-divider.c b/drivers/clk/clk-fractional-divider.c
new file mode 100644
index 0000000..59b98aa
--- /dev/null
+++ b/drivers/clk/clk-fractional-divider.c
@@ -0,0 +1,152 @@
+/*
+ * Copyright (C) 2014 Intel Corporation
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ * Adjustable fractional divider clock implementation.
+ * Output rate = (m / n) * parent_rate.
+ */
+
+#include <common.h>
+#include <io.h>
+#include <malloc.h>
+#include <linux/clk.h>
+#include <linux/err.h>
+#include <linux/gcd.h>
+#include <linux/math64.h>
+#include <linux/barebox-wrapper.h>
+
+#define to_clk_fd(_hw) container_of(_hw, struct clk_fractional_divider, clk)
+
+struct clk_fractional_divider {
+	struct clk	clk;
+	void __iomem	*reg;
+	u8		mshift;
+	u32		mmask;
+	u8		nshift;
+	u32		nmask;
+	u8		flags;
+};
+
+static unsigned long clk_fd_recalc_rate(struct clk *hw,
+					unsigned long parent_rate)
+{
+	struct clk_fractional_divider *fd = to_clk_fd(hw);
+	u32 val, m, n;
+	u64 ret;
+
+	val = readl(fd->reg);
+
+	m = (val & fd->mmask) >> fd->mshift;
+	n = (val & fd->nmask) >> fd->nshift;
+
+	ret = (u64)parent_rate * m;
+	do_div(ret, n);
+
+	return ret;
+}
+
+static long clk_fd_round_rate(struct clk *hw, unsigned long rate,
+			      unsigned long *prate)
+{
+	struct clk_fractional_divider *fd = to_clk_fd(hw);
+	unsigned maxn = (fd->nmask >> fd->nshift) + 1;
+	unsigned div;
+
+	if (!rate || rate >= *prate)
+		return *prate;
+
+	div = gcd(*prate, rate);
+
+	while ((*prate / div) > maxn) {
+		div <<= 1;
+		rate <<= 1;
+	}
+
+	return rate;
+}
+
+static int clk_fd_set_rate(struct clk *hw, unsigned long rate,
+			   unsigned long parent_rate)
+{
+	struct clk_fractional_divider *fd = to_clk_fd(hw);
+	unsigned long div;
+	unsigned n, m;
+	u32 val;
+
+	div = gcd(parent_rate, rate);
+	m = rate / div;
+	n = parent_rate / div;
+
+	val = readl(fd->reg);
+	val &= ~(fd->mmask | fd->nmask);
+	val |= (m << fd->mshift) | (n << fd->nshift);
+	writel(val, fd->reg);
+
+	return 0;
+}
+
+const struct clk_ops clk_fractional_divider_ops = {
+	.recalc_rate = clk_fd_recalc_rate,
+	.round_rate = clk_fd_round_rate,
+	.set_rate = clk_fd_set_rate,
+};
+EXPORT_SYMBOL_GPL(clk_fractional_divider_ops);
+
+struct clk *clk_fractional_divider_alloc(
+		const char *name, const char *parent_name, unsigned long flags,
+		void __iomem *reg, u8 mshift, u8 mwidth, u8 nshift, u8 nwidth,
+		u8 clk_divider_flags)
+{
+	struct clk_fractional_divider *fd;
+
+	fd = xzalloc(sizeof(*fd));
+
+	fd->reg = reg;
+	fd->mshift = mshift;
+	fd->mmask = (BIT(mwidth) - 1) << mshift;
+	fd->nshift = nshift;
+	fd->nmask = (BIT(nwidth) - 1) << nshift;
+	fd->flags = clk_divider_flags;
+	fd->clk.name = name;
+	fd->clk.ops = &clk_fractional_divider_ops;
+	fd->clk.flags = flags;
+	fd->clk.parent_names = parent_name ? &parent_name : NULL;
+	fd->clk.num_parents = parent_name ? 1 : 0;
+
+	return &fd->clk;
+}
+
+void clk_fractional_divider_free(struct clk *clk_fd)
+{
+	struct clk_fractional_divider *fd = to_clk_fd(clk_fd);
+
+	free(fd);
+}
+
+struct clk *clk_fractional_divider(
+		const char *name, const char *parent_name, unsigned long flags,
+		void __iomem *reg, u8 mshift, u8 mwidth, u8 nshift, u8 nwidth,
+		u8 clk_divider_flags)
+{
+	struct clk *fd;
+	int ret;
+
+	fd = clk_fractional_divider_alloc(name, parent_name, flags,
+		reg, mshift, mwidth, nshift, nwidth,
+		clk_divider_flags);
+
+	if (IS_ERR(fd))
+		return fd;
+
+	ret = clk_register(fd);
+	if (ret) {
+		clk_fractional_divider_free(fd);
+		return ERR_PTR(ret);
+	}
+
+	return fd;
+}
+EXPORT_SYMBOL_GPL(clk_register_fractional_divider);
diff --git a/include/linux/clk.h b/include/linux/clk.h
index fe8ae5c..de2d4a5 100644
--- a/include/linux/clk.h
+++ b/include/linux/clk.h
@@ -260,6 +260,15 @@ struct clk *clk_divider_table(const char *name,
 struct clk *clk_fixed_factor(const char *name,
 		const char *parent, unsigned int mult, unsigned int div,
 		unsigned flags);
+struct clk *clk_fractional_divider_alloc(
+		const char *name, const char *parent_name, unsigned long flags,
+		void __iomem *reg, u8 mshift, u8 mwidth, u8 nshift, u8 nwidth,
+		u8 clk_divider_flags);
+struct clk *clk_fractional_divider(
+		const char *name, const char *parent_name, unsigned long flags,
+		void __iomem *reg, u8 mshift, u8 mwidth, u8 nshift, u8 nwidth,
+		u8 clk_divider_flags);
+void clk_fractional_divider_free(struct clk *clk_fd);
 
 struct clk *clk_mux_alloc(const char *name, void __iomem *reg,
 		u8 shift, u8 width, const char **parents, u8 num_parents,
-- 
2.1.4