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Message-ID: <20111114021359.GA25796@b20223-02.ap.freescale.net>
Date: Mon, 14 Nov 2011 10:14:00 +0800
From: Richard Zhao <richard.zhao@...aro.org>
To: Rob Herring <robherring2@...il.com>
CC: Grant Likely <grant.likely@...retlab.ca>,
<devicetree-discuss@...ts.ozlabs.org>,
Sascha Hauer <kernel@...gutronix.de>,
<linux-arm-kernel@...ts.infradead.org>,
<linux-kernel@...r.kernel.org>
Subject: Re: [RFC 6/8] of: add clock providers
On Tue, Nov 08, 2011 at 08:49:42PM -0600, Rob Herring wrote:
> On 11/08/2011 07:19 PM, Grant Likely wrote:
> > 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@...retlab.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 is duplicated below.
>
> > +
> > +
> > +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>;
>
> The code is using "clock-frequency" here.
>
> > + 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>;
>
> There's a mismatch in #clock-cells size and this.
osc #clock-cells is 1. "0" is one cell too. Nothing wrong. Correct my understanding?
>
> > + 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);
>
> How about:
>
> if (provider->get)
> clk = provider->get(clkspec, provider->data);
> else
> clk = provider->data;
>
>
> Or a default get function can do this.
>
> > + 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 */
> > +
>
>
> _______________________________________________
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> linux-arm-kernel@...ts.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
>
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