[PATCH v4 4/5] clk: dt: binding for basic divider clock
Mike Turquette
mturquette at linaro.org
Thu Aug 22 01:53:12 EDT 2013
Devicetree binding for the basic clock divider, plus the setup function
to register the clock. Based on the existing fixed-clock binding.
Tero Kristo contributed helpful bug fixes to this patch.
Signed-off-by: Mike Turquette <mturquette at linaro.org>
Tested-by: Heiko Stuebner <heiko at sntech.de>
Reviewed-by: Heiko Stuebner <heiko at sntech.de>
---
Changes since v3:
* replaced underscores with dashes in DT property names
* bail from of clock setup function early if of_iomap fails
* removed unecessary explict cast
.../devicetree/bindings/clock/divider-clock.txt | 90 ++++++++++++++++++++
drivers/clk/clk-divider.c | 97 +++++++++++++++++++++-
include/linux/clk-provider.h | 2 +
3 files changed, 188 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..ac80724
--- /dev/null
+++ b/Documentation/devicetree/bindings/clock/divider-clock.txt
@@ -0,0 +1,90 @@
+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-starts-at-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
+
+index-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
+- bit-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
+- bit-shift : number of bits to shift the bit-mask, defaults to
+ (ffs(mask) - 1) if not present
+- minimum-divider : min divisor for dividing the input clock rate, only
+ needed if the first divisor is offset from the default value
+- maximum-divider : max divisor for dividing the input clock rate, only
+ needed if the max divisor is less than (mask + 1).
+- index-starts-at-one : valid divisor programming starts at 1, not zero
+- index-power-of-two : valid divisor programming must be a power of two
+- index-allow-zero : implies index-one, and programming zero results in
+ divide-by-one
+- hiword-mask : lower half of the register programs the divider, upper
+ half of the register indicates bits that were updated in the lower
+ half
+
+Examples:
+ clock_foo: clock_foo at 4a008100 {
+ compatible = "divider-clock";
+ #clock-cells = <0>;
+ clocks = <&clock_baz>;
+ reg = <0x4a008100 0x4>
+ mask = <0x3>
+ maximum-divider = <3>
+ };
+
+ 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 2791a2b..f95abc8 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
@@ -342,3 +344,96 @@ struct clk *clk_register_divider_table(struct device *dev, const char *name,
((1 << width) - 1), clk_divider_flags, table, lock);
}
EXPORT_SYMBOL_GPL(clk_register_divider_table);
+
+#ifdef CONFIG_OF
+struct clk_div_table *of_clk_get_div_table(struct device_node *node)
+{
+ int i;
+ u32 table_size;
+ struct clk_div_table *table;
+ const __be32 *tablespec;
+ u32 val;
+
+ tablespec = of_get_property(node, "table", &table_size);
+
+ if (!tablespec)
+ return NULL;
+
+ table_size /= sizeof(struct clk_div_table);
+
+ 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++) {
+ of_property_read_u32_index(node, "table", i * 2, &val);
+ table[i].div = val;
+ of_property_read_u32_index(node, "table", i * 2 + 1, &val);
+ table[i].val = val;
+ }
+
+ return table;
+}
+
+/**
+ * of_divider_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;
+ u32 mask = 0;
+ u32 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 (!reg) {
+ pr_err("%s: no memory mapped for property reg\n", __func__);
+ return;
+ }
+
+ if (of_property_read_u32(node, "bit-mask", &mask)) {
+ pr_err("%s: missing bit-mask property for %s\n", __func__, node->name);
+ return;
+ }
+
+ if (of_property_read_u32(node, "bit-shift", &shift)) {
+ shift = __ffs(mask);
+ pr_debug("%s: bit-shift property defaults to 0x%x for %s\n",
+ __func__, shift, node->name);
+ }
+
+ if (of_property_read_bool(node, "index-starts-at-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;
+
+ if (of_property_read_bool(node, "hiword-mask"))
+ clk_divider_flags |= CLK_DIVIDER_HIWORD_MASK;
+
+ table = of_clk_get_div_table(node);
+ if (IS_ERR(table))
+ return;
+
+ clk = _register_divider(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 e019212..218d923 100644
--- a/include/linux/clk-provider.h
+++ b/include/linux/clk-provider.h
@@ -301,6 +301,8 @@ 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
More information about the linux-arm-kernel
mailing list