[PATCH v4 1/5] clk: Add a basic multiplier clock
Maxime Ripard
maxime.ripard at free-electrons.com
Mon Oct 12 13:43:26 PDT 2015
Some clocks are using a multiplier component, however, unlike their mux,
gate or divider counterpart, these factors don't have a basic clock
implementation.
This leads to code duplication across platforms that want to use that kind
of clocks, and the impossibility to use the composite clocks with such a
clock without defining your own rate operations.
Create such a driver in order to remove these issues, and hopefully factor
the implementations, reducing code size across platforms and consolidating
the various implementations.
Signed-off-by: Maxime Ripard <maxime.ripard at free-electrons.com>
---
drivers/clk/Makefile | 1 +
drivers/clk/clk-multiplier.c | 181 +++++++++++++++++++++++++++++++++++++++++++
include/linux/clk-provider.h | 42 ++++++++++
3 files changed, 224 insertions(+)
create mode 100644 drivers/clk/clk-multiplier.c
diff --git a/drivers/clk/Makefile b/drivers/clk/Makefile
index d08b3e5985be..0b2101039508 100644
--- a/drivers/clk/Makefile
+++ b/drivers/clk/Makefile
@@ -6,6 +6,7 @@ obj-$(CONFIG_COMMON_CLK) += clk-divider.o
obj-$(CONFIG_COMMON_CLK) += clk-fixed-factor.o
obj-$(CONFIG_COMMON_CLK) += clk-fixed-rate.o
obj-$(CONFIG_COMMON_CLK) += clk-gate.o
+obj-$(CONFIG_COMMON_CLK) += clk-multiplier.o
obj-$(CONFIG_COMMON_CLK) += clk-mux.o
obj-$(CONFIG_COMMON_CLK) += clk-composite.o
obj-$(CONFIG_COMMON_CLK) += clk-fractional-divider.o
diff --git a/drivers/clk/clk-multiplier.c b/drivers/clk/clk-multiplier.c
new file mode 100644
index 000000000000..75fee96ea1ee
--- /dev/null
+++ b/drivers/clk/clk-multiplier.c
@@ -0,0 +1,181 @@
+/*
+ * Copyright (C) 2015 Maxime Ripard <maxime.ripard at free-electrons.com>
+ *
+ * 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.
+ */
+
+#include <linux/bitops.h>
+#include <linux/clk-provider.h>
+#include <linux/err.h>
+#include <linux/export.h>
+#include <linux/kernel.h>
+#include <linux/of.h>
+#include <linux/slab.h>
+
+#define to_clk_multiplier(_hw) container_of(_hw, struct clk_multiplier, hw)
+
+static unsigned long __get_mult(struct clk_multiplier *mult,
+ unsigned long rate,
+ unsigned long parent_rate)
+{
+ if (mult->flags & CLK_MULTIPLIER_ROUND_CLOSEST)
+ return DIV_ROUND_CLOSEST(rate, parent_rate);
+
+ return rate / parent_rate;
+}
+
+static unsigned long clk_multiplier_recalc_rate(struct clk_hw *hw,
+ unsigned long parent_rate)
+{
+ struct clk_multiplier *mult = to_clk_multiplier(hw);
+ unsigned long val;
+
+ val = clk_readl(mult->reg) >> mult->shift;
+ val &= GENMASK(mult->width, 0);
+
+ if (!val && mult->flags & CLK_MULTIPLIER_ZERO_BYPASS)
+ val = 1;
+
+ return parent_rate * val;
+}
+
+static bool __is_best_rate(unsigned long rate, unsigned long new,
+ unsigned long best, unsigned long flags)
+{
+ if (flags & CLK_MULTIPLIER_ROUND_CLOSEST)
+ return abs(rate - new) < abs(rate - best);
+
+ return new >= rate && new < best;
+}
+
+static unsigned long __bestmult(struct clk_hw *hw, unsigned long rate,
+ unsigned long *best_parent_rate,
+ u8 width, unsigned long flags)
+{
+ unsigned long orig_parent_rate = *best_parent_rate;
+ unsigned long parent_rate, current_rate, best_rate = ~0;
+ unsigned int i, bestmult = 0;
+
+ if (!(clk_hw_get_flags(hw) & CLK_SET_RATE_PARENT))
+ return rate / *best_parent_rate;
+
+ for (i = 1; i < ((1 << width) - 1); i++) {
+ if (rate * i == orig_parent_rate) {
+ /*
+ * This is the best case for us if we have a
+ * perfect match without changing the parent
+ * rate.
+ */
+ *best_parent_rate = orig_parent_rate;
+ return i;
+ }
+
+ parent_rate = clk_hw_round_rate(clk_hw_get_parent(hw),
+ rate / i);
+ current_rate = parent_rate * i;
+
+ if (__is_best_rate(rate, current_rate, best_rate, flags)) {
+ bestmult = i;
+ best_rate = current_rate;
+ *best_parent_rate = parent_rate;
+ }
+ }
+
+ return bestmult;
+}
+
+static long clk_multiplier_round_rate(struct clk_hw *hw, unsigned long rate,
+ unsigned long *parent_rate)
+{
+ struct clk_multiplier *mult = to_clk_multiplier(hw);
+ unsigned long factor = __bestmult(hw, rate, parent_rate,
+ mult->width, mult->flags);
+
+ return *parent_rate * factor;
+}
+
+static int clk_multiplier_set_rate(struct clk_hw *hw, unsigned long rate,
+ unsigned long parent_rate)
+{
+ struct clk_multiplier *mult = to_clk_multiplier(hw);
+ unsigned long factor = __get_mult(mult, rate, parent_rate);
+ unsigned long flags = 0;
+ unsigned long val;
+
+ if (mult->lock)
+ spin_lock_irqsave(mult->lock, flags);
+ else
+ __acquire(mult->lock);
+
+ val = clk_readl(mult->reg);
+ val &= ~GENMASK(mult->width + mult->shift, mult->shift);
+ val |= factor << mult->shift;
+ clk_writel(val, mult->reg);
+
+ if (mult->lock)
+ spin_unlock_irqrestore(mult->lock, flags);
+ else
+ __release(mult->lock);
+
+ return 0;
+}
+
+const struct clk_ops clk_multiplier_ops = {
+ .recalc_rate = clk_multiplier_recalc_rate,
+ .round_rate = clk_multiplier_round_rate,
+ .set_rate = clk_multiplier_set_rate,
+};
+EXPORT_SYMBOL_GPL(clk_multiplier_ops);
+
+struct clk *clk_register_multiplier(struct device *dev, const char *name,
+ const char *parent_name,
+ unsigned long flags,
+ void __iomem *reg, u8 shift, u8 width,
+ u8 clk_mult_flags, spinlock_t *lock)
+{
+ struct clk_init_data init;
+ struct clk_multiplier *mult;
+ struct clk *clk;
+
+ mult = kmalloc(sizeof(*mult), GFP_KERNEL);
+ if (!mult)
+ return ERR_PTR(-ENOMEM);
+
+ init.name = name;
+ init.ops = &clk_multiplier_ops;
+ init.flags = flags | CLK_IS_BASIC;
+ init.parent_names = &parent_name;
+ init.num_parents = 1;
+
+ mult->reg = reg;
+ mult->shift = shift;
+ mult->width = width;
+ mult->flags = clk_mult_flags;
+ mult->lock = lock;
+ mult->hw.init = &init;
+
+ clk = clk_register(dev, &mult->hw);
+ if (IS_ERR(clk))
+ kfree(mult);
+
+ return clk;
+}
+EXPORT_SYMBOL_GPL(clk_register_multiplier);
+
+void clk_unregister_multiplier(struct clk *clk)
+{
+ struct clk_multiplier *mult;
+ struct clk_hw *hw;
+
+ hw = __clk_get_hw(clk);
+ if (!hw)
+ return;
+
+ mult = to_clk_multiplier(hw);
+
+ clk_unregister(clk);
+ kfree(mult);
+}
+EXPORT_SYMBOL_GPL(clk_unregister_multiplier);
diff --git a/include/linux/clk-provider.h b/include/linux/clk-provider.h
index 3ecc07d0da77..6a7dfe33a317 100644
--- a/include/linux/clk-provider.h
+++ b/include/linux/clk-provider.h
@@ -518,6 +518,48 @@ struct clk *clk_register_fractional_divider(struct device *dev,
void __iomem *reg, u8 mshift, u8 mwidth, u8 nshift, u8 nwidth,
u8 clk_divider_flags, spinlock_t *lock);
+/**
+ * struct clk_multiplier - adjustable multiplier clock
+ *
+ * @hw: handle between common and hardware-specific interfaces
+ * @reg: register containing the multiplier
+ * @shift: shift to the multiplier bit field
+ * @width: width of the multiplier bit field
+ * @lock: register lock
+ *
+ * Clock with an adjustable multiplier affecting its output frequency.
+ * Implements .recalc_rate, .set_rate and .round_rate
+ *
+ * Flags:
+ * CLK_MULTIPLIER_ZERO_BYPASS - By default, the multiplier is the value read
+ * from the register, with 0 being a valid value effectively
+ * zeroing the output clock rate. If CLK_MULTIPLIER_ZERO_BYPASS is
+ * set, then a null multiplier will be considered as a bypass,
+ * leaving the parent rate unmodified.
+ * CLK_MULTIPLIER_ROUND_CLOSEST - Makes the best calculated divider to be
+ * rounded to the closest integer instead of the down one.
+ */
+struct clk_multiplier {
+ struct clk_hw hw;
+ void __iomem *reg;
+ u8 shift;
+ u8 width;
+ u8 flags;
+ spinlock_t *lock;
+};
+
+#define CLK_MULTIPLIER_ZERO_BYPASS BIT(0)
+#define CLK_MULTIPLIER_ROUND_CLOSEST BIT(1)
+
+extern const struct clk_ops clk_multiplier_ops;
+
+struct clk *clk_register_multiplier(struct device *dev, const char *name,
+ const char *parent_name,
+ unsigned long flags,
+ void __iomem *reg, u8 shift, u8 width,
+ u8 clk_mult_flags, spinlock_t *lock);
+void clk_unregister_multiplier(struct clk *clk);
+
/***
* struct clk_composite - aggregate clock of mux, divider and gate clocks
*
--
2.5.3
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