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    Subject[RFC 6/8] of: add clock providers
    Date
    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.

    Signed-off-by: Grant Likely <grant.likely@secretlab.ca>
    ---
    .../devicetree/bindings/clock/clock-bindings.txt | 109 +++++++++++++++++
    drivers/of/Kconfig | 6 +
    drivers/of/Makefile | 1 +
    drivers/of/clock.c | 129 ++++++++++++++++++++
    include/linux/of_clk.h | 37 ++++++
    5 files changed, 282 insertions(+), 0 deletions(-)
    create mode 100644 Documentation/devicetree/bindings/clock/clock-bindings.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..4770c7e
    --- /dev/null
    +++ b/Documentation/devicetree/bindings/clock/clock-bindings.txt
    @@ -0,0 +1,109 @@
    +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-name: 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-names 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-names property.
    +
    +For example:
    +
    + oscillator {
    + #clock-cells = <1>;
    + clock-output-name = "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:
    +clock-input: List of phandle and clock specifier pairs, one pair
    + for each clock input to the device.
    +clock-input-name: List of clock input name strings sorted in the same
    + order as the clock-input property. Consumers drivers
    + will use clock-input-name to match clock input names
    + with clock-input specifiers.
    +
    +For example:
    +
    + uart {
    + clock-input = <&osc 1> <&ref 0>;
    + clock-input-name = "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>;
    + frequency = <32678>;
    + clock-output-name = "osc";
    + };
    +
    + /* phase-locked-loop device, generates a higher frequency clock
    + * from the external oscillator reference */
    + pll: pll {
    + compatible = "some-pll-interface"
    + #clock-cells = <1>;
    + clock-input = <&osc 0>;
    + clock-input-name = "ref";
    + reg = <0x4c000 0x1000>;
    + clock-output-name = "pll", "pll-switched";
    + };
    +
    + /* UART, using the low frequency oscillator for the baud clock,
    + * and the high frequency switched PLL output for register
    + * clocking */
    + uart {
    + compatible = "fsl,imx-uart";
    + reg = <0xa000 0x1000>;
    + interrupts = <33>;
    + clock-input = <&osc 0>, <&pll 1>;
    + clock-input-name = "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/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..542b9e4
    --- /dev/null
    +++ b/drivers/of/clock.c
    @@ -0,0 +1,129 @@
    +/*
    + * 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, "clock", "#clock-cells", index,
    + &clkspec);
    + if (rc)
    + return NULL;
    +
    + clk = __of_clk_get_from_provider(&clkspec);
    + of_node_put(clkspec.np);
    + return clk;
    +}
    +
    +struct clk *of_clk_get_by_name(struct device_node *np, const char *name)
    +{
    + int index = 0;
    +
    + if (name)
    + index = of_property_match_string(np, "clock-input-names", name);
    + return of_clk_get(np, index);
    +}
    +
    diff --git a/include/linux/of_clk.h b/include/linux/of_clk.h
    new file mode 100644
    index 0000000..e476a5f
    --- /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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