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Message-Id: <1398428541-912-2-git-send-email-heikki.krogerus@linux.intel.com>
Date: Fri, 25 Apr 2014 15:22:20 +0300
From: Heikki Krogerus <heikki.krogerus@...ux.intel.com>
To: "Rafael J. Wysocki" <rjw@...ysocki.net>,
Mike Turquette <mturquette@...aro.org>
Cc: Len Brown <lenb@...nel.org>,
Mika Westerberg <mika.westerberg@...el.com>,
Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
Loic Poulain <loic.poulain@...el.com>,
linux-acpi@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH 1/2] clk: new basic clk type for fractional divider
Fractional divider clocks are fairly common. This adds basic
type for them.
Signed-off-by: Heikki Krogerus <heikki.krogerus@...ux.intel.com>
---
drivers/clk/Makefile | 1 +
drivers/clk/clk-fractional-divider.c | 132 +++++++++++++++++++++++++++++++++++
include/linux/clk-provider.h | 31 ++++++++
3 files changed, 164 insertions(+)
create mode 100644 drivers/clk/clk-fractional-divider.c
diff --git a/drivers/clk/Makefile b/drivers/clk/Makefile
index 5f8a287..0745059 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 0000000..a4dd873
--- /dev/null
+++ b/drivers/clk/clk-fractional-divider.c
@@ -0,0 +1,132 @@
+/*
+ * 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/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;
+ unsigned n, m;
+ u32 val;
+
+ 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;
+
+ return parent_rate / n * m;
+}
+
+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 maxdiv = (fd->nmask >> fd->nshift) + 1;
+ unsigned div;
+
+ if (!rate || rate > *prate)
+ return *prate;
+
+ div = gcd(*prate, rate);
+
+ while ((*prate / div) > maxdiv) {
+ 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) {
+ pr_err("%s: could not allocate fractional divider clk\n",
+ __func__);
+ 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 5119174..fb4eca6 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
*
--
2.0.0.rc0
--
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