3 files changed, 167 insertions, 0 deletions

diff --git a/drivers/clk/Makefile b/drivers/clk/Makefile
index 5f8a28735c96..0745059b1834 100644
--- a/drivers/clk/Makefile
+++ b/drivers/clk/Makefile
@@ -8,6 +8,7 @@ obj-$(CONFIG_COMMON_CLK)	+= clk-fixed-rate.o
 obj-$(CONFIG_COMMON_CLK)        += clk-gate.o
 obj-$(CONFIG_COMMON_CLK)        += clk-mux.o
 obj-$(CONFIG_COMMON_CLK)        += clk-composite.o
+obj-$(CONFIG_COMMON_CLK)        += clk-fractional-divider.o
 
 # hardware specific clock types
 # please keep this section sorted lexicographically by file/directory path name
diff --git a/drivers/clk/clk-fractional-divider.c b/drivers/clk/clk-fractional-divider.c
new file mode 100644
index 000000000000..ede685ca0d20
--- /dev/null
+++ b/drivers/clk/clk-fractional-divider.c
@@ -0,0 +1,135 @@
+/*
+ * 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 <linux/clk-provider.h>
+#include <linux/module.h>
+#include <linux/device.h>
+#include <linux/slab.h>
+#include <linux/gcd.h>
+
+#define to_clk_fd(_hw) container_of(_hw, struct clk_fractional_divider, hw)
+
+static unsigned long clk_fd_recalc_rate(struct clk_hw *hw,
+                                        unsigned long parent_rate)
+{
+        struct clk_fractional_divider *fd = to_clk_fd(hw);
+        unsigned long flags = 0;
+        u32 val, m, n;
+        u64 ret;
+
+        if (fd->lock)
+                spin_lock_irqsave(fd->lock, flags);
+
+        val = clk_readl(fd->reg);
+
+        if (fd->lock)
+                spin_unlock_irqrestore(fd->lock, flags);
+
+        m = (val & fd->mmask) >> fd->mshift;
+        n = (val & fd->nmask) >> fd->nshift;
+
+        ret = parent_rate * m;
+        do_div(ret, n);
+
+        return ret;
+}
+
+static long clk_fd_round_rate(struct clk_hw *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 *hw, unsigned long rate,
+                           unsigned long parent_rate)
+{
+        struct clk_fractional_divider *fd = to_clk_fd(hw);
+        unsigned long flags = 0;
+        unsigned long div;
+        unsigned n, m;
+        u32 val;
+
+        div = gcd(parent_rate, rate);
+        m = rate / div;
+        n = parent_rate / div;
+
+        if (fd->lock)
+                spin_lock_irqsave(fd->lock, flags);
+
+        val = clk_readl(fd->reg);
+        val &= ~(fd->mmask | fd->nmask);
+        val |= (m << fd->mshift) | (n << fd->nshift);
+        clk_writel(val, fd->reg);
+
+        if (fd->lock)
+                spin_unlock_irqrestore(fd->lock, flags);
+
+        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_register_fractional_divider(struct device *dev,
+                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, spinlock_t *lock)
+{
+        struct clk_fractional_divider *fd;
+        struct clk_init_data init;
+        struct clk *clk;
+
+        fd = kzalloc(sizeof(*fd), GFP_KERNEL);
+        if (!fd) {
+                dev_err(dev, "could not allocate fractional divider clk\n");
+                return ERR_PTR(-ENOMEM);
+        }
+
+        init.name = name;
+        init.ops = &clk_fractional_divider_ops;
+        init.flags = flags | CLK_IS_BASIC;
+        init.parent_names = parent_name ? &parent_name : NULL;
+        init.num_parents = parent_name ? 1 : 0;
+
+        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->lock = lock;
+        fd->hw.init = &init;
+
+        clk = clk_register(dev, &fd->hw);
+        if (IS_ERR(clk))
+                kfree(fd);
+
+        return clk;
+}
+EXPORT_SYMBOL_GPL(clk_register_fractional_divider);
diff --git a/include/linux/clk-provider.h b/include/linux/clk-provider.h
index 511917416fb0..fb4eca6907cd 100644
--- a/include/linux/clk-provider.h
+++ b/include/linux/clk-provider.h
@@ -413,6 +413,37 @@ 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_fractional_divider - adjustable fractional divider clock
+ *
+ * @hw:         handle between common and hardware-specific interfaces
+ * @reg:        register containing the divider
+ * @mshift:     shift to the numerator bit field
+ * @mwidth:     width of the numerator bit field
+ * @nshift:     shift to the denominator bit field
+ * @nwidth:     width of the denominator bit field
+ * @lock:       register lock
+ *
+ * Clock with adjustable fractional divider affecting its output frequency.
+ */
+
+struct clk_fractional_divider {
+        struct clk_hw   hw;
+        void __iomem    *reg;
+        u8              mshift;
+        u32             mmask;
+        u8              nshift;
+        u32             nmask;
+        u8              flags;
+        spinlock_t      *lock;
+};
+
+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,
+                void __iomem *reg, u8 mshift, u8 mwidth, u8 nshift, u8 nwidth,
+                u8 clk_divider_flags, spinlock_t *lock);
+
 /***
  * struct clk_composite - aggregate clock of mux, divider and gate clocks
  *