[v2,4/5] clk: dt: binding for basic divider clock

Commit Message

Mike Turquette June 17, 2013, 2:58 a.m. UTC

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 <[e-mail]>
---
Changes since v1:
* mask is u32, shift is u8
* use bit mask instead of bitfield width
* DT property names use dashes instead of underscores
* DT property names are more verbose
* added minimum/maximum divider values to binding
* shift property is optional in binding and can be auto-generated from a
  full 32-bit mask

 .../devicetree/bindings/clock/divider-clock.txt    | 87 +++++++++++++++++++++
 drivers/clk/clk-divider.c                          | 90 +++++++++++++++++++++-
 include/linux/clk-provider.h                       |  2 +
 3 files changed, 178 insertions(+), 1 deletion(-)
 create mode 100644 Documentation/devicetree/bindings/clock/divider-clock.txt

Comments

Heiko Stuebner June 20, 2013, 9:22 p.m. UTC | #1

Hi Mike,

Am Montag, 17. Juni 2013, 04:58:24 schrieb Mike Turquette:
> 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 <[e-mail]>
> ---
> Changes since v1:
> * mask is u32, shift is u8
> * use bit mask instead of bitfield width
> * DT property names use dashes instead of underscores
> * DT property names are more verbose
> * added minimum/maximum divider values to binding
> * shift property is optional in binding and can be auto-generated from a
>   full 32-bit mask
> 
>  .../devicetree/bindings/clock/divider-clock.txt    | 87
> +++++++++++++++++++++ drivers/clk/clk-divider.c                          |
> 90 +++++++++++++++++++++- include/linux/clk-provider.h                    
>   |  2 +
>  3 files changed, 178 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..96bea07
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/clock/divider-clock.txt
> @@ -0,0 +1,87 @@
> +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.

this doesn't match the current code that is taking the first as bit-value
and the second as divider.


> +
> +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
> +
> +Examples:
> +	clock_foo: clock_foo@4a008100 {
> +		compatible = "divider-clock";
> +		#clock-cells = <0>;
> +		clocks = <&clock_baz>;
> +		reg = <0x4a008100 0x4>
> +		mask = <0x3>
> +		maximum-divider = <3>
> +	};
> +
> +	clock_bar: clock_bar@4a008108 {
> +		#clock-cells = <0>;
> +		compatible = "divider-clock";
> +		clocks = <&clock_foo>;
> +		reg = <0x4a008108 0x4>;
> +		mask = <0x1>;
> +		shift = <0>;
> +		table = < 4 0 >, < 8 1 >;
> +	};

the shift and mask properties should probably also get their "bit-" additions.

Also, if you really want to use the u8 as type, it seems like the property
must also get a "/bits/ 8" prefix, making it:

			bit-shift = /bits/ 8 <6>;

so the example should probably reflect this. Without this the
of_property_read_u8 returns wrong values.


> diff --git a/drivers/clk/clk-divider.c b/drivers/clk/clk-divider.c
> index ac9cb7f..8c42c7f 100644
> --- a/drivers/clk/clk-divider.c
> +++ b/drivers/clk/clk-divider.c
> @@ -1,7 +1,7 @@
>  /*
>   * Copyright (C) 2011 Sascha Hauer, Pengutronix <[e-mail]>
>   * Copyright (C) 2011 Richard Zhao, Linaro <[e-mail]>
> - * Copyright (C) 2011-2012 Mike Turquette, Linaro Ltd
> <[e-mail]> + * Copyright (C) 2011-2013 Mike Turquette, Linaro
> Ltd <[e-mail]> *
>   * 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
> @@ -340,3 +342,89 @@ struct clk *clk_register_divider_table(struct device
> *dev, const char *name, return _register_divider(dev, name, parent_name,
> flags, reg, shift, ((1 << width) - 1), 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");

I don't really understand what this should do ... especially what are the "#clock-cells" doing there?

Of course the function also doesn't work for my
			table = <2 0>, <4 1>, <8 2>, <16 3>;
table.


> +
> +	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)))

wouldn't this always read the same values? It does not seem to iterate thru all the table entries.



> { +			table[i].val = pair[0];
> +			table[i].div = pair[1];
> +		}
> +	}
> +
> +	return table;
> +}
> +

how about:

struct clk_div_table *of_clk_get_div_table(struct device_node *node)
{
	int i;
	int table_size = 0;
	struct clk_div_table *table;
	const __be32 *list;

	list = of_get_property(node, "table", &table_size);
	table_size /= sizeof(*list);

	if (table_size < 2 || table_size % 2)
		return NULL;

	table_size /= 2;

	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++) {
		table[i].div = be32_to_cpu(*list++);
		table[i].val = be32_to_cpu(*list++);
	}

	return table;
}


Heiko

Patch

diff --git a/Documentation/devicetree/bindings/clock/divider-clock.txt b/Documentation/devicetree/bindings/clock/divider-clock.txt
new file mode 100644
index 0000000..96bea07
--- /dev/null
+++ b/Documentation/devicetree/bindings/clock/divider-clock.txt
@@ -0,0 +1,87 @@ 
+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
+
+Examples:
+	clock_foo: clock_foo@4a008100 {
+		compatible = "divider-clock";
+		#clock-cells = <0>;
+		clocks = <&clock_baz>;
+		reg = <0x4a008100 0x4>
+		mask = <0x3>
+		maximum-divider = <3>
+	};
+
+	clock_bar: clock_bar@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 ac9cb7f..8c42c7f 100644
--- a/drivers/clk/clk-divider.c
+++ b/drivers/clk/clk-divider.c
@@ -1,7 +1,7 @@ 
 /*
  * Copyright (C) 2011 Sascha Hauer, Pengutronix <[e-mail]>
  * Copyright (C) 2011 Richard Zhao, Linaro <[e-mail]>
- * Copyright (C) 2011-2012 Mike Turquette, Linaro Ltd <[e-mail]>
+ * Copyright (C) 2011-2013 Mike Turquette, Linaro Ltd <[e-mail]>
  *
  * 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
@@ -340,3 +342,89 @@  struct clk *clk_register_divider_table(struct device *dev, const char *name,
 	return _register_divider(dev, name, parent_name, flags, reg, shift,
 			((1 << width) - 1), 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_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;
+	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_u32(node, "bit-mask", &mask)) {
+		pr_err("%s: missing bit-mask property for %s\n", __func__, node->name);
+		return;
+	}
+
+	if (of_property_read_u8(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;
+
+	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 24a04b8..723ce69 100644
--- a/include/linux/clk-provider.h
+++ b/include/linux/clk-provider.h
@@ -293,6 +293,8 @@  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
  *