File-copy from v4.4.100
This is the result of 'cp' from a linux-stable tree with the 'v4.4.100'
tag checked out (commit 26d6298789e695c9f627ce49a7bbd2286405798a) on
git://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
Please refer to that tree for all history prior to this point.
Change-Id: I8a9ee2aea93cd29c52c847d0ce33091a73ae6afe
diff --git a/drivers/clk/clk-fractional-divider.c b/drivers/clk/clk-fractional-divider.c
new file mode 100644
index 0000000..5c4955e
--- /dev/null
+++ b/drivers/clk/clk-fractional-divider.c
@@ -0,0 +1,157 @@
+/*
+ * 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.
+ * Uses rational best approximation algorithm.
+ */
+
+#include <linux/clk-provider.h>
+#include <linux/module.h>
+#include <linux/device.h>
+#include <linux/slab.h>
+#include <linux/rational.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;
+ unsigned long m, n;
+ u32 val;
+ u64 ret;
+
+ if (fd->lock)
+ spin_lock_irqsave(fd->lock, flags);
+ else
+ __acquire(fd->lock);
+
+ val = clk_readl(fd->reg);
+
+ if (fd->lock)
+ spin_unlock_irqrestore(fd->lock, flags);
+ else
+ __release(fd->lock);
+
+ m = (val & fd->mmask) >> fd->mshift;
+ n = (val & fd->nmask) >> fd->nshift;
+
+ if (!n || !m)
+ return parent_rate;
+
+ ret = (u64)parent_rate * m;
+ do_div(ret, n);
+
+ return ret;
+}
+
+static long clk_fd_round_rate(struct clk_hw *hw, unsigned long rate,
+ unsigned long *parent_rate)
+{
+ struct clk_fractional_divider *fd = to_clk_fd(hw);
+ unsigned long scale;
+ unsigned long m, n;
+ u64 ret;
+
+ if (!rate || rate >= *parent_rate)
+ return *parent_rate;
+
+ /*
+ * Get rate closer to *parent_rate to guarantee there is no overflow
+ * for m and n. In the result it will be the nearest rate left shifted
+ * by (scale - fd->nwidth) bits.
+ */
+ scale = fls_long(*parent_rate / rate - 1);
+ if (scale > fd->nwidth)
+ rate <<= scale - fd->nwidth;
+
+ rational_best_approximation(rate, *parent_rate,
+ GENMASK(fd->mwidth - 1, 0), GENMASK(fd->nwidth - 1, 0),
+ &m, &n);
+
+ ret = (u64)*parent_rate * m;
+ do_div(ret, n);
+
+ return ret;
+}
+
+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 m, n;
+ u32 val;
+
+ rational_best_approximation(rate, parent_rate,
+ GENMASK(fd->mwidth - 1, 0), GENMASK(fd->nwidth - 1, 0),
+ &m, &n);
+
+ if (fd->lock)
+ spin_lock_irqsave(fd->lock, flags);
+ else
+ __acquire(fd->lock);
+
+ 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);
+ else
+ __release(fd->lock);
+
+ 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)
+ 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->mwidth = mwidth;
+ fd->mmask = GENMASK(mwidth - 1, 0) << mshift;
+ fd->nshift = nshift;
+ fd->nwidth = nwidth;
+ fd->nmask = GENMASK(nwidth - 1, 0) << 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);