clk: add a fixed factor clock

Having fixed factors/dividers in hardware is a common pattern, so
add a basic clock type doing this. It basically describes a fixed
factor clock using a nominator and a denominator.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
Reviewed-by: Viresh Kumar <viresh.kumar@st.com>
Tested-by: Shawn Guo <shawn.guo@linaro.org>
[mturquette@linaro.org: constify parent_names in static init macro]
[mturquette@linaro.org: copy/paste bug from mux in static init macro]
[mturquette@linaro.org: fix error handling in clk_register_fixed_factor]
[mturquette@linaro.org: improve division accuracy; thanks to Saravana]
Signed-off-by: Mike Turquette <mturquette@linaro.org>

drivers/clk/Makefile

@@ -1,4 +1,4 @@
 
 obj-$(CONFIG_CLKDEV_LOOKUP)	+= clkdev.o
 obj-$(CONFIG_COMMON_CLK)	+= clk.o clk-fixed-rate.o clk-gate.o \
-				   clk-mux.o clk-divider.o
+				   clk-mux.o clk-divider.o clk-fixed-factor.o

drivers/clk/clk-fixed-factor.c

@@ -0,0 +1,95 @@
+/*
+ * Copyright (C) 2011 Sascha Hauer, Pengutronix <s.hauer@pengutronix.de>
+ *
+ * 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.
+ *
+ * Standard functionality for the common clock API.
+ */
+#include <linux/module.h>
+#include <linux/clk-provider.h>
+#include <linux/slab.h>
+#include <linux/err.h>
+
+/*
+ * DOC: basic fixed multiplier and divider clock that cannot gate
+ *
+ * Traits of this clock:
+ * prepare - clk_prepare only ensures that parents are prepared
+ * enable - clk_enable only ensures that parents are enabled
+ * rate - rate is fixed.  clk->rate = parent->rate / div * mult
+ * parent - fixed parent.  No clk_set_parent support
+ */
+
+#define to_clk_fixed_factor(_hw) container_of(_hw, struct clk_fixed_factor, hw)
+
+static unsigned long clk_factor_recalc_rate(struct clk_hw *hw,
+		unsigned long parent_rate)
+{
+	struct clk_fixed_factor *fix = to_clk_fixed_factor(hw);
+
+	return parent_rate * fix->mult / fix->div;
+}
+
+static long clk_factor_round_rate(struct clk_hw *hw, unsigned long rate,
+				unsigned long *prate)
+{
+	struct clk_fixed_factor *fix = to_clk_fixed_factor(hw);
+
+	if (__clk_get_flags(hw->clk) & CLK_SET_RATE_PARENT) {
+		unsigned long best_parent;
+
+		best_parent = (rate / fix->mult) * fix->div;
+		*prate = __clk_round_rate(__clk_get_parent(hw->clk),
+				best_parent);
+	}
+
+	return (*prate / fix->div) * fix->mult;
+}
+
+static int clk_factor_set_rate(struct clk_hw *hw, unsigned long rate,
+				unsigned long parent_rate)
+{
+	return 0;
+}
+
+struct clk_ops clk_fixed_factor_ops = {
+	.round_rate = clk_factor_round_rate,
+	.set_rate = clk_factor_set_rate,
+	.recalc_rate = clk_factor_recalc_rate,
+};
+EXPORT_SYMBOL_GPL(clk_fixed_factor_ops);
+
+struct clk *clk_register_fixed_factor(struct device *dev, const char *name,
+		const char *parent_name, unsigned long flags,
+		unsigned int mult, unsigned int div)
+{
+	struct clk_fixed_factor *fix;
+	struct clk_init_data init;
+	struct clk *clk;
+
+	fix = kmalloc(sizeof(*fix), GFP_KERNEL);
+	if (!fix) {
+		pr_err("%s: could not allocate fixed factor clk\n", __func__);
+		return ERR_PTR(-ENOMEM);
+	}
+
+	/* struct clk_fixed_factor assignments */
+	fix->mult = mult;
+	fix->div = div;
+	fix->hw.init = &init;
+
+	init.name = name;
+	init.ops = &clk_fixed_factor_ops;
+	init.flags = flags;
+	init.parent_names = &parent_name;
+	init.num_parents = 1;
+
+	clk = clk_register(dev, &fix->hw);
+
+	if (IS_ERR(clk))
+		kfree(fix);
+
+	return clk;
+}

include/linux/clk-private.h

@@ -143,6 +143,26 @@ struct clk {
 	DEFINE_CLK(_name, clk_mux_ops, _flags, _parent_names,	\
 			_parents);
 
+#define DEFINE_CLK_FIXED_FACTOR(_name, _parent_name,		\
+				_parent_ptr, _flags,		\
+				_mult, _div)			\
+	static struct clk _name;				\
+	static const char *_name##_parent_names[] = {		\
+		_parent_name,					\
+	};							\
+	static struct clk *_name##_parents[] = {		\
+		_parent_ptr,					\
+	};							\
+	static struct clk_fixed_factor _name##_hw = {		\
+		.hw = {						\
+			.clk = &_name,				\
+		},						\
+		.mult = _mult,					\
+		.div = _div,					\
+	};							\
+	DEFINE_CLK(_name, clk_fixed_factor_ops, _flags,		\
+			_name##_parent_names, _name##_parents);
+
 /**
  * __clk_init - initialize the data structures in a struct clk
  * @dev:	device initializing this clk, placeholder for now

include/linux/clk-provider.h

@@ -276,6 +276,29 @@ struct clk *clk_register_mux(struct device *dev, const char *name,
 		void __iomem *reg, u8 shift, u8 width,
 		u8 clk_mux_flags, spinlock_t *lock);
 
+/**
+ * struct clk_fixed_factor - fixed multiplier and divider clock
+ *
+ * @hw:		handle between common and hardware-specific interfaces
+ * @mult:	multiplier
+ * @div:	divider
+ *
+ * Clock with a fixed multiplier and divider. The output frequency is the
+ * parent clock rate divided by div and multiplied by mult.
+ * Implements .recalc_rate, .set_rate and .round_rate
+ */
+
+struct clk_fixed_factor {
+	struct clk_hw	hw;
+	unsigned int	mult;
+	unsigned int	div;
+};
+
+extern struct clk_ops clk_fixed_factor_ops;
+struct clk *clk_register_fixed_factor(struct device *dev, const char *name,
+		const char *parent_name, unsigned long flags,
+		unsigned int mult, unsigned int div);
+
 /**
  * clk_register - allocate a new clock, register it and return an opaque cookie
  * @dev: device that is registering this clock