Subject: [PATCH 2/7] of: add clock providers

From: [email-masked] (Grant Likely)
Date: Fri, 06 Apr 2012 21:18:40 -0700

On Tue, 13 Mar 2012 18:22:22 -0500, Rob Herring <[email-masked]> wrote:
> From: Grant Likely <[email-masked]>
> 
> Based on work by Ben Herrenschmidt and Jeremy Kerr, this patch adds an
> of_clk_get function to allow platforms to retrieve clock data from the
> device tree.
> 
> Platform register a provider through of_clk_add_provider, which will be
> called when a device references the provider's OF node for a clock
> reference.
> 
> v3: - Clarified documentation
> 
> v2: - fixed errant ';' causing compile error
>     - Editorial fixes from Shawn Guo
>     - merged in adding lookup to clkdev
>     - changed property names to match established convention. After
>       working with the binding a bit it really made more sense to follow the
>       lead of 'reg', 'gpios' and 'interrupts' by making the input simply
>       'clocks' & 'clock-names' instead of 'clock-input-*', and to only use
>       clock-output* for the producer nodes. (Sorry Shawn, this will mean
>       you need to change some code, but it should be trivial)
>     - Add ability to inherit clocks from parent nodes by using an empty
>       'clock-ranges' property.  Useful for busses.  I could use some feedback
>       on the new property name, 'clock-ranges' doesn't feel right to me.
> 
> Signed-off-by: Grant Likely <[email-masked]>
> Reviewed-by: Shawn Guo <[email-masked]>
> Cc: Rob Herring <[email-masked]>
> Cc: Sascha Hauer <[email-masked]>
> Cc: Mike Turquette <[email-masked]>

Hi Rob,

Thanks for respinning this patch.  Since you're actually using it, do
you want to take over getting it into mainline?

> ---
>  .../devicetree/bindings/clock/clock-bindings.txt   |  116 ++++++++++++++
>  .../devicetree/bindings/clock/fixed-clock.txt      |   21 +++
>  drivers/clk/clkdev.c                               |    9 +
>  drivers/of/Kconfig                                 |    6 +
>  drivers/of/Makefile                                |    1 +
>  drivers/of/clock.c                                 |  165 ++++++++++++++++++++

I would actually like to see this file moved into drivers/clk.  I
don't think there is any need anymore to collect OF support code into
drivers/of.  I plan to move the spi and gpio support code into
drivers/spi and drivers/gpio respectively.

g.

>  include/linux/of_clk.h                             |   37 +++++
>  7 files changed, 355 insertions(+), 0 deletions(-)
>  create mode 100644 Documentation/devicetree/bindings/clock/clock-bindings.txt
>  create mode 100644 Documentation/devicetree/bindings/clock/fixed-clock.txt
>  create mode 100644 drivers/of/clock.c
>  create mode 100644 include/linux/of_clk.h
> 
> diff --git a/Documentation/devicetree/bindings/clock/clock-bindings.txt b/Documentation/devicetree/bindings/clock/clock-bindings.txt
> new file mode 100644
> index 0000000..3cb6746
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/clock/clock-bindings.txt
> @@ -0,0 +1,116 @@
> +This binding is a work-in-progress, and are based on some experimental
> +work by benh[1].
> +
> +Sources of clock signal can be represented by any node in the device
> +tree.  Those nodes are designated as clock providers.  Clock consumer
> +nodes use a phandle and clock specifier pair to connect clock provider
> +outputs to clock inputs.  Similar to the gpio specifiers, a clock
> +specifier is an array of one more more cells identifying the clock
> +output on a device.  The length of a clock specifier is defined by the
> +value of a #clock-cells property in the clock provider node.
> +
> +[1] http://patchwork.ozlabs.org/patch/31551/
> +
> +==Clock providers==
> +
> +Required properties:
> +#clock-cells:	   Number of cells in a clock specifier; typically will be
> +		   set to 1
> +
> +Optional properties:
> +clock-output-names: Recommended to be a list of strings of clock output signal
> +		    names indexed by the first cell in the clock specifier.
> +		    However, the meaning of clock-output-name is domain
> +		    specific to the clock provider, and is only provided to
> +		    encourage using the same meaning for the majority of clock
> +		    providers.  This format may not work for clock providers
> +		    using a complex clock specifier format.  In those cases it
> +		    is recommended to omit this property and create a binding
> +		    specific names property.
> +
> +		    Clock consumer nodes must never directly reference
> +		    the provider's clock-output-name property.
> +
> +For example:
> +
> +    oscillator {
> +        #clock-cells = <1>;
> +        clock-output-names = "ckil", "ckih";
> +    };
> +
> +- this node defines a device with two clock outputs, the first named
> +  "ckil" and the second named "ckih".  Consumer nodes always reference
> +  clocks by index. The names should reflect the clock output signal
> +  names for the device.
> +
> +==Clock consumers==
> +
> +Required properties:
> +clocks:		List of phandle and clock specifier pairs, one pair
> +		for each clock input to the device.  Note: if the
> +		clock provider specifies '0' for #clock-cells, then
> +		only the phandle portion of the pair will appear.
> +
> +Optional properties:
> +clock-names:	List of clock input name strings sorted in the same
> +		order as the clocks property.  Consumers drivers
> +		will use clock-names to match clock input names
> +		with clocks specifiers.
> +clock-ranges:	Empty property indicating that child nodes can inherit named
> +		clocks from this node. Useful for bus nodes to provide a
> +		clock to their children.
> +
> +For example:
> +
> +    device {
> +        clocks = <&osc 1>, <&ref 0>;
> +        clock-names = "baud", "register";
> +    };
> +
> +
> +This represents a device with two clock inputs, named "baud" and "register".
> +The baud clock is connected to output 1 of the &osc device, and the register
> +clock is connected to output 0 of the &ref.
> +
> +==Example==
> +
> +    /* external oscillator */
> +    osc: oscillator {
> +        compatible = "fixed-clock";
> +        #clock-cells = <1>;
> +        clock-frequency  = <32678>;
> +        clock-output-names = "osc";
> +    };
> +
> +    /* phase-locked-loop device, generates a higher frequency clock
> +     * from the external oscillator reference */
> +    pll: pll at 4c000 {
> +        compatible = "vendor,some-pll-interface"
> +        #clock-cells = <1>;
> +        clocks = <&osc 0>;
> +        clock-names = "ref";
> +        reg = <0x4c000 0x1000>;
> +        clock-output-names = "pll", "pll-switched";
> +    };
> +
> +    /* UART, using the low frequency oscillator for the baud clock,
> +     * and the high frequency switched PLL output for register
> +     * clocking */
> +    uart at a000 {
> +        compatible = "fsl,imx-uart";
> +        reg = <0xa000 0x1000>;
> +        interrupts = <33>;
> +        clocks = <&osc 0>, <&pll 1>;
> +        clock-names = "baud", "register";
> +    };
> +
> +This DT fragment defines three devices: an external oscillator to provide a
> +low-frequency reference clock, a PLL device to generate a higher frequency
> +clock signal, and a UART.
> +
> +* The oscillator is fixed-frequency, and provides one clock output, named "osc".
> +* The PLL is both a clock provider and a clock consumer. It uses the clock
> +  signal generated by the external oscillator, and provides two output signals
> +  ("pll" and "pll-switched").
> +* The UART has its baud clock connected the external oscillator and its
> +  register clock connected to the PLL clock (the "pll-switched" signal)
> diff --git a/Documentation/devicetree/bindings/clock/fixed-clock.txt b/Documentation/devicetree/bindings/clock/fixed-clock.txt
> new file mode 100644
> index 0000000..9a75342
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/clock/fixed-clock.txt
> @@ -0,0 +1,21 @@
> +Binding for simple fixed-rate clock sources.
> +
> +This binding uses the common clock binding[1].
> +
> +[1] Documentation/devicetree/bindings/clock/fixed-clock.txt
> +
> +Required properties:
> +- compatible : shall be "fixed-clock".
> +- #clock-cells : from common clock binding; shall be set to 0.
> +- clock-frequency : frequency of clock in Hz. May be multiple cells.
> +
> +Optional properties:
> +- gpios : From common gpio binding; gpio connection to clock enable pin.
> +- clock-output-names : From common clock binding
> +
> +Example:
> +	clock {
> +		compatible = "fixed-clock";
> +		#clock-cells = <0>;
> +		clock-frequency = <1000000000>;
> +	};
> diff --git a/drivers/clk/clkdev.c b/drivers/clk/clkdev.c
> index 6db161f..43628d0 100644
> --- a/drivers/clk/clkdev.c
> +++ b/drivers/clk/clkdev.c
> @@ -19,6 +19,8 @@
>  #include <linux/mutex.h>
>  #include <linux/clk.h>
>  #include <linux/clkdev.h>
> +#include <linux/of.h>
> +#include <linux/of_clk.h>
>  
>  static LIST_HEAD(clocks);
>  static DEFINE_MUTEX(clocks_mutex);
> @@ -78,6 +80,13 @@ EXPORT_SYMBOL(clk_get_sys);
>  struct clk *clk_get(struct device *dev, const char *con_id)
>  {
>  	const char *dev_id = dev ? dev_name(dev) : NULL;
> +	struct clk *clk;
> +
> +	if (dev) {
> +		clk = of_clk_get_by_name(dev->of_node, con_id);
> +		if (clk && __clk_get(clk))
> +			return clk;
> +	}
>  
>  	return clk_get_sys(dev_id, con_id);
>  }
> diff --git a/drivers/of/Kconfig b/drivers/of/Kconfig
> index 268163d..b49ab9c 100644
> --- a/drivers/of/Kconfig
> +++ b/drivers/of/Kconfig
> @@ -47,6 +47,12 @@ config OF_IRQ
>  	def_bool y
>  	depends on !SPARC
>  
> +config OF_CLOCK
> +	def_bool y
> +	depends on HAVE_CLK
> +	help
> +	  OpenFirmware clock accessors
> +
>  config OF_DEVICE
>  	def_bool y
>  
> diff --git a/drivers/of/Makefile b/drivers/of/Makefile
> index a73f5a5..e7ad1e9 100644
> --- a/drivers/of/Makefile
> +++ b/drivers/of/Makefile
> @@ -5,6 +5,7 @@ obj-$(CONFIG_OF_ADDRESS)  += address.o
>  obj-$(CONFIG_OF_IRQ)    += irq.o
>  obj-$(CONFIG_OF_DEVICE) += device.o platform.o
>  obj-$(CONFIG_OF_GPIO)   += gpio.o
> +obj-$(CONFIG_OF_CLOCK)	+= clock.o
>  obj-$(CONFIG_OF_I2C)	+= of_i2c.o
>  obj-$(CONFIG_OF_NET)	+= of_net.o
>  obj-$(CONFIG_OF_SPI)	+= of_spi.o
> diff --git a/drivers/of/clock.c b/drivers/of/clock.c
> new file mode 100644
> index 0000000..6519e96
> --- /dev/null
> +++ b/drivers/of/clock.c
> @@ -0,0 +1,165 @@
> +/*
> + * Clock infrastructure for device tree platforms
> + */
> +
> +#include <linux/clk.h>
> +#include <linux/err.h>
> +#include <linux/errno.h>
> +#include <linux/module.h>
> +#include <linux/of.h>
> +#include <linux/of_clk.h>
> +#include <linux/list.h>
> +#include <linux/mutex.h>
> +#include <linux/slab.h>
> +#include <linux/device.h>
> +
> +/**
> + * struct of_clk_provider - Clock provider registration structure
> + * @link: Entry in global list of clock providers
> + * @node: Pointer to device tree node of clock provider
> + * @get: Get clock callback.  Returns NULL or a struct clk for the
> + *       given clock specifier
> + * @data: context pointer to be passed into @get callback
> + */
> +struct of_clk_provider {
> +	struct list_head link;
> +
> +	struct device_node *node;
> +	struct clk *(*get)(struct of_phandle_args *clkspec, void *data);
> +	void *data;
> +};
> +
> +static LIST_HEAD(of_clk_providers);
> +static DEFINE_MUTEX(of_clk_lock);
> +
> +/**
> + * of_clk_add_provider() - Register a clock provider for a node
> + * @np: Device node pointer associated with clock provider
> + * @clk_src_get: callback for decoding clock
> + * @data: context pointer for @clk_src_get callback.
> + */
> +int of_clk_add_provider(struct device_node *np,
> +			struct clk *(*clk_src_get)(struct of_phandle_args *clkspec,
> +						   void *data),
> +			void *data)
> +{
> +	struct of_clk_provider *cp;
> +
> +	cp = kzalloc(sizeof(struct of_clk_provider), GFP_KERNEL);
> +	if (!cp)
> +		return -ENOMEM;
> +
> +	cp->node = of_node_get(np);
> +	cp->data = data;
> +	cp->get = clk_src_get;
> +
> +	mutex_lock(&of_clk_lock);
> +	list_add(&cp->link, &of_clk_providers);
> +	mutex_unlock(&of_clk_lock);
> +	pr_debug("Added clock from %s\n", np->full_name);
> +
> +	return 0;
> +}
> +
> +/**
> + * of_clk_del_provider() - Remove a previously registered clock provider
> + * @np: Device node pointer associated with clock provider
> + */
> +void of_clk_del_provider(struct device_node *np)
> +{
> +	struct of_clk_provider *cp;
> +
> +	mutex_lock(&of_clk_lock);
> +	list_for_each_entry(cp, &of_clk_providers, link) {
> +		if (cp->node == np) {
> +			list_del(&cp->link);
> +			of_node_put(cp->node);
> +			kfree(cp);
> +			break;
> +		}
> +	}
> +	mutex_unlock(&of_clk_lock);
> +}
> +
> +static struct clk *__of_clk_get_from_provider(struct of_phandle_args *clkspec)
> +{
> +	struct of_clk_provider *provider;
> +	struct clk *clk = NULL;
> +
> +	/* Check if we have such a provider in our array */
> +	mutex_lock(&of_clk_lock);
> +	list_for_each_entry(provider, &of_clk_providers, link) {
> +		if (provider->node == clkspec->np)
> +			clk = provider->get(clkspec, provider->data);
> +		if (clk)
> +			break;
> +	}
> +	mutex_unlock(&of_clk_lock);
> +
> +	return clk;
> +}
> +
> +struct clk *of_clk_get(struct device_node *np, int index)
> +{
> +	struct of_phandle_args clkspec;
> +	struct clk *clk;
> +	int rc;
> +
> +	if (index < 0)
> +		return NULL;
> +
> +	rc = of_parse_phandle_with_args(np, "clocks", "#clock-cells", index,
> +					&clkspec);
> +	if (rc)
> +		return NULL;
> +
> +	clk = __of_clk_get_from_provider(&clkspec);
> +	of_node_put(clkspec.np);
> +	return clk;
> +}
> +
> +/**
> + * of_clk_get_by_name() - Parse and lookup a clock referenced by a device node
> + * @np: pointer to clock consumer node
> + * @name: name of consumer's clock input, or NULL for the first clock reference
> + *
> + * This function parses the clocks and clock-names properties,
> + * and uses them to look up the struct clk from the registered list of clock
> + * providers.
> + */
> +struct clk *of_clk_get_by_name(struct device_node *np, const char *name)
> +{
> +	struct clk *clk = NULL;
> +
> +	/* Walk up the tree of devices looking for a clock that matches */
> +	while (np) {
> +		int index = 0;
> +
> +		/*
> +		 * For named clocks, first look up the name in the
> +		 * "clock-names" property.  If it cannot be found, then
> +		 * index will be an error code, and of_clk_get() will fail.
> +		 */
> +		if (name)
> +			index = of_property_match_string(np, "clock-names", name);
> +		clk = of_clk_get(np, index);
> +		if (clk)
> +			break;
> +		else if (name && index >= 0) {
> +			pr_err("ERROR: could not get clock %s:%s(%i)\n",
> +				 np->full_name, name ? name : "", index);
> +			return NULL;
> +		}
> +
> +		/*
> +		 * No matching clock found on this node.  If the parent node
> +		 * has a "clock-ranges" property, then we can try one of its
> +		 * clocks.
> +		 */
> +		np = np->parent;
> +		if (np && !of_get_property(np, "clock-ranges", NULL))
> +			break;
> +	}
> +
> +	return clk;
> +}
> diff --git a/include/linux/of_clk.h b/include/linux/of_clk.h
> new file mode 100644
> index 0000000..dcbd27b
> --- /dev/null
> +++ b/include/linux/of_clk.h
> @@ -0,0 +1,37 @@
> +/*
> + * Clock infrastructure for device tree platforms
> + */
> +#ifndef __OF_CLK_H
> +#define __OF_CLK_H
> +
> +struct device;
> +struct clk;
> +
> +#ifdef CONFIG_OF_CLOCK
> +
> +struct device_node;
> +
> +int of_clk_add_provider(struct device_node *np,
> +			struct clk *(*clk_src_get)(struct of_phandle_args *args,
> +						   void *data),
> +			void *data);
> +
> +void of_clk_del_provider(struct device_node *np);
> +
> +struct clk *of_clk_get(struct device_node *np, int index);
> +struct clk *of_clk_get_by_name(struct device_node *np, const char *name);
> +
> +#else
> +static struct clk *of_clk_get(struct device_node *np, int index)
> +{
> +	return NULL;
> +}
> +
> +static struct clk *of_clk_get_by_name(struct device_node *np, const char *name)
> +{
> +	return NULL;
> +}
> +#endif
> +
> +#endif /* __OF_CLK_H */
> +
> -- 
> 1.7.5.4
> 
> 
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-- 
Grant Likely, B.Sc, P.Eng.
Secret Lab Technologies,Ltd.