[PATCH RFC 3/3] clk: dt: binding for basic divider clock
Mike Turquette
mturquette at linaro.org
Mon Jun 3 13:53:10 EDT 2013
Devicetree binding for the basic clock divider, plus the setup function
to register the clock. Based on the existing fixed-clock binding.
Signed-off-by: Mike Turquette <mturquette at linaro.org>
---
.../devicetree/bindings/clock/divider-clock.txt | 80 ++++++++++++++++++++
drivers/clk/clk-divider.c | 88 +++++++++++++++++++++-
include/linux/clk-provider.h | 2 +
3 files changed, 169 insertions(+), 1 deletion(-)
create mode 100644 Documentation/devicetree/bindings/clock/divider-clock.txt
diff --git a/Documentation/devicetree/bindings/clock/divider-clock.txt b/Documentation/devicetree/bindings/clock/divider-clock.txt
new file mode 100644
index 0000000..31e9273
--- /dev/null
+++ b/Documentation/devicetree/bindings/clock/divider-clock.txt
@@ -0,0 +1,80 @@
+Binding for simple divider clock.
+
+This binding uses the common clock binding[1]. It assumes a
+register-mapped adjustable clock rate divider that does not gate and has
+only one input clock or parent. By default the value programmed into
+the register is one less than the actual divisor value. E.g:
+
+register value actual divisor value
+0 1
+1 2
+2 3
+
+This assumption may be modified by the following optional properties:
+
+index_one - valid divisor values start at 1, not the default of 0. E.g:
+register value actual divisor value
+1 1
+2 2
+3 3
+
+index_power_of_two - valid divisor values are powers of two. E.g:
+register value actual divisor value
+0 1
+1 2
+2 4
+
+allow_zero - same as index_one, but zero is divide-by-1. E.g:
+register value actual divisor value
+0 1
+1 1
+2 2
+
+Additionally a table of valid dividers may be supplied like so:
+
+ table = <4 0>, <8, 1>;
+
+where the first value in the pair is the divider and the second value is
+the programmed register bitfield.
+
+The binding must also provide the register to control the divider and
+the mask for the corresponding control bits. Optionally the number of
+bits to shift that mask, if necessary. If the shift value is missing it
+is the same as supplying a zero shift.
+
+[1] Documentation/devicetree/bindings/clock/clock-bindings.txt
+
+Required properties:
+- compatible : shall be "divider-clock".
+- #clock-cells : from common clock binding; shall be set to 0.
+- clocks : link to phandle of parent clock
+- reg : base address for register controlling adjustable divider
+- mask : arbitrary bitmask for programming the adjustable divider
+
+Optional properties:
+- clock-output-names : From common clock binding.
+- table : array of integer pairs defining divisors & bitfield values
+- shift : number of bits to shift the mask, defaults to 0 if not present
+- index_one : valid divisor programming starts at 1, not zero
+- index_power_of_two : valid divisor programming must be a power of two
+- allow_zero : implies index_one, and programming zero results in
+ divide-by-one
+
+Examples:
+ clock_foo: clock_foo at 4a008100 {
+ compatible = "divider-clock";
+ #clock-cells = <0>;
+ clocks = <&clock_baz>;
+ reg = <0x4a008100 0x4>
+ mask = <0x3>
+ };
+
+ clock_bar: clock_bar at 4a008108 {
+ #clock-cells = <0>;
+ compatible = "divider-clock";
+ clocks = <&clock_foo>;
+ reg = <0x4a008108 0x4>;
+ mask = <0x1>;
+ shift = <0>;
+ table = < 4 0 >, < 8 1 >;
+ };
diff --git a/drivers/clk/clk-divider.c b/drivers/clk/clk-divider.c
index 6d96741..3b76591 100644
--- a/drivers/clk/clk-divider.c
+++ b/drivers/clk/clk-divider.c
@@ -1,7 +1,7 @@
/*
* Copyright (C) 2011 Sascha Hauer, Pengutronix <s.hauer at pengutronix.de>
* Copyright (C) 2011 Richard Zhao, Linaro <richard.zhao at linaro.org>
- * Copyright (C) 2011-2012 Mike Turquette, Linaro Ltd <mturquette at linaro.org>
+ * Copyright (C) 2011-2013 Mike Turquette, Linaro Ltd <mturquette at linaro.org>
*
* 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
@@ -17,6 +17,8 @@
#include <linux/err.h>
#include <linux/string.h>
#include <linux/log2.h>
+#include <linux/of.h>
+#include <linux/of_address.h>
/*
* DOC: basic adjustable divider clock that cannot gate
@@ -320,3 +322,87 @@ struct clk *clk_register_divider_table(struct device *dev, const char *name,
return _register_divider(dev, name, parent_name, flags, reg, shift,
width, clk_divider_flags, table, lock);
}
+
+#ifdef CONFIG_OF
+struct clk_div_table *of_clk_get_div_table(struct device_node *node)
+{
+ int i;
+ int table_size = 0;
+ struct clk_div_table *table;
+ u32 pair[2];
+
+ table_size = of_count_phandle_with_args(node, "table", "#clock-cells");
+
+ if (table_size < 1)
+ return NULL;
+
+ table = kzalloc(sizeof(struct clk_div_table) * table_size, GFP_KERNEL);
+ if (!table) {
+ pr_err("%s: unable to allocate memory for %s table\n", __func__, node->name);
+ return NULL;
+ }
+
+ for (i = 0; i < table_size; i++) {
+ if (!of_property_read_u32_array(node, "table", pair, ARRAY_SIZE(pair))) {
+ table[i].val = pair[0];
+ table[i].div = pair[1];
+ }
+ }
+
+ return table;
+}
+
+/**
+ * of_div_clk_setup() - Setup function for simple div rate clock
+ */
+void of_divider_clk_setup(struct device_node *node)
+{
+ struct clk *clk;
+ const char *clk_name = node->name;
+ void __iomem *reg;
+ const char *parent_name;
+ u8 clk_divider_flags = 0;
+ u8 mask = 0;
+ u8 shift = 0;
+ struct clk_div_table *table;
+
+ of_property_read_string(node, "clock-output-names", &clk_name);
+
+ parent_name = of_clk_get_parent_name(node, 0);
+
+ reg = of_iomap(node, 0);
+
+ if (of_property_read_u8(node, "mask", &mask)) {
+ pr_err("%s: missing mask property for %s\n", __func__, node->name);
+ return;
+ }
+
+ if (of_property_read_u8(node, "shift", &shift))
+ pr_debug("%s: missing shift property defaults to zero for %s\n",
+ __func__, node->name);
+
+ if (of_property_read_bool(node, "index_one"))
+ clk_divider_flags |= CLK_DIVIDER_ONE_BASED;
+
+ if (of_property_read_bool(node, "index_power_of_two"))
+ clk_divider_flags |= CLK_DIVIDER_POWER_OF_TWO;
+
+ if (of_property_read_bool(node, "index_allow_zero"))
+ clk_divider_flags |= CLK_DIVIDER_ALLOW_ZERO;
+
+ table = of_clk_get_div_table(node);
+ if (IS_ERR(table))
+ return;
+
+ clk = clk_register_divider_table(NULL, clk_name,
+ parent_name, 0,
+ reg, shift, mask,
+ clk_divider_flags, table,
+ NULL);
+
+ if (!IS_ERR(clk))
+ of_clk_add_provider(node, of_clk_src_simple_get, clk);
+}
+EXPORT_SYMBOL_GPL(of_divider_clk_setup);
+CLK_OF_DECLARE(divider_clk, "divider-clock", of_divider_clk_setup);
+#endif
diff --git a/include/linux/clk-provider.h b/include/linux/clk-provider.h
index 9c404c2..63521e7 100644
--- a/include/linux/clk-provider.h
+++ b/include/linux/clk-provider.h
@@ -283,6 +283,8 @@ struct clk *clk_register_divider_table(struct device *dev, const char *name,
u8 clk_divider_flags, const struct clk_div_table *table,
spinlock_t *lock);
+void of_divider_clk_setup(struct device_node *node);
+
/**
* struct clk_mux - multiplexer clock
*
--
1.8.1.2
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