[PATCH v2 1/7] clk: Add a generic clock infrastructure
Richard Zhao
richard.zhao at freescale.com
Tue Oct 11 07:25:27 EDT 2011
On Thu, Sep 22, 2011 at 03:26:56PM -0700, Mike Turquette wrote:
> From: Jeremy Kerr <jeremy.kerr at canonical.com>
>
> We currently have ~21 definitions of struct clk in the ARM architecture,
> each defined on a per-platform basis. This makes it difficult to define
> platform- (or architecture-) independent clock sources without making
> assumptions about struct clk, and impossible to compile two
> platforms with different struct clks into a single image.
>
> This change is an effort to unify struct clk where possible, by defining
> a common struct clk, and a set of clock operations. Different clock
> implementations can set their own operations, and have a standard
> interface for generic code. The callback interface is exposed to the
> kernel proper, while the clock implementations only need to be seen by
> the platform internals.
>
> The interface is split into two halves:
>
> * struct clk, which is the generic-device-driver interface. This
> provides a set of functions which drivers may use to request
> enable/disable, query or manipulate in a hardware-independent manner.
>
> * struct clk_hw and struct clk_hw_ops, which is the hardware-specific
> interface. Clock drivers implement the ops, which allow the core
> clock code to implement the generic 'struct clk' API.
>
> This allows us to share clock code among platforms, and makes it
> possible to dynamically create clock devices in platform-independent
> code.
>
> Platforms can enable the generic struct clock through
> CONFIG_GENERIC_CLK. In this case, the clock infrastructure consists of a
> common, opaque struct clk, and a set of clock operations (defined per
> type of clock):
>
> struct clk_hw_ops {
> int (*prepare)(struct clk_hw *);
> void (*unprepare)(struct clk_hw *);
> int (*enable)(struct clk_hw *);
> void (*disable)(struct clk_hw *);
> unsigned long (*recalc_rate)(struct clk_hw *);
> int (*set_rate)(struct clk_hw *,
> unsigned long, unsigned long *);
> long (*round_rate)(struct clk_hw *, unsigned long);
> int (*set_parent)(struct clk_hw *, struct clk *);
> struct clk * (*get_parent)(struct clk_hw *);
> };
>
> Platform clock code can register a clock through clk_register, passing a
> set of operations, and a pointer to hardware-specific data:
>
> struct clk_hw_foo {
> struct clk_hw clk;
> void __iomem *enable_reg;
> };
>
> #define to_clk_foo(c) offsetof(c, clk_hw_foo, clk)
>
> static int clk_foo_enable(struct clk_hw *clk)
> {
> struct clk_foo *foo = to_clk_foo(clk);
> raw_writeb(foo->enable_reg, 1);
> return 0;
> }
>
> struct clk_hw_ops clk_foo_ops = {
> .enable = clk_foo_enable,
> };
>
> And in the platform initialisation code:
>
> struct clk_foo my_clk_foo;
>
> void init_clocks(void)
> {
> my_clk_foo.enable_reg = ioremap(...);
>
> clk_register(&clk_foo_ops, &my_clk_foo, NULL);
> }
>
> Changes from Thomas Gleixner <tglx at linutronix.de>.
>
> The common clock definitions are based on a development patch from Ben
> Herrenschmidt <benh at kernel.crashing.org>.
>
> TODO:
>
> * We don't keep any internal reference to the clock topology at present.
>
> Signed-off-by: Jeremy Kerr <jeremy.kerr at canonical.com>
> Signed-off-by: Thomas Gleixner <tglx at linutronix.de>
> Signed-off-by: Mark Brown <broonie at opensource.wolfsonmicro.com>
> Signed-off-by: Mike Turquette <mturquette at ti.com>
> ---
> Changes since v1:
> Create a dummy clk_unregister and prototype/document it and clk_register
> Constify struct clk_hw_ops
> Remove spinlock.h header, include kernel.h
> Use EOPNOTSUPP instead of ENOTSUPP
> Add might_sleep to clk_prepare/clk_unprepare stubs
> Properly init children hlist and child_node
> Whitespace and typo fixes
>
> drivers/clk/Kconfig | 3 +
> drivers/clk/Makefile | 1 +
> drivers/clk/clk.c | 232 ++++++++++++++++++++++++++++++++++++++++++++++++++
> drivers/clk/clkdev.c | 7 ++
> include/linux/clk.h | 140 +++++++++++++++++++++++++++---
> 5 files changed, 371 insertions(+), 12 deletions(-)
> create mode 100644 drivers/clk/clk.c
>
> diff --git a/drivers/clk/Kconfig b/drivers/clk/Kconfig
> index 3530927..c53ed59 100644
> --- a/drivers/clk/Kconfig
> +++ b/drivers/clk/Kconfig
> @@ -5,3 +5,6 @@ config CLKDEV_LOOKUP
>
> config HAVE_MACH_CLKDEV
> bool
> +
> +config GENERIC_CLK
> + bool
> diff --git a/drivers/clk/Makefile b/drivers/clk/Makefile
> index 07613fa..570d5b9 100644
> --- a/drivers/clk/Makefile
> +++ b/drivers/clk/Makefile
> @@ -1,2 +1,3 @@
>
> obj-$(CONFIG_CLKDEV_LOOKUP) += clkdev.o
> +obj-$(CONFIG_GENERIC_CLK) += clk.o
> diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
> new file mode 100644
> index 0000000..1cd7315
> --- /dev/null
> +++ b/drivers/clk/clk.c
> @@ -0,0 +1,232 @@
> +/*
> + * Copyright (C) 2010-2011 Canonical Ltd <jeremy.kerr at canonical.com>
> + *
> + * 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
> + * published by the Free Software Foundation.
> + *
> + * Standard functionality for the common clock API.
> + */
> +
> +#include <linux/clk.h>
> +#include <linux/module.h>
> +#include <linux/mutex.h>
> +#include <linux/slab.h>
> +#include <linux/spinlock.h>
> +
> +struct clk {
> + const char *name;
> + const struct clk_hw_ops *ops;
> + struct clk_hw *hw;
> + unsigned int enable_count;
> + unsigned int prepare_count;
> + struct clk *parent;
> + unsigned long rate;
> +};
> +
> +static DEFINE_SPINLOCK(enable_lock);
> +static DEFINE_MUTEX(prepare_lock);
> +
> +static void __clk_unprepare(struct clk *clk)
> +{
> + if (!clk)
> + return;
> +
> + if (WARN_ON(clk->prepare_count == 0))
> + return;
> +
> + if (--clk->prepare_count > 0)
> + return;
> +
> + WARN_ON(clk->enable_count > 0);
> +
> + if (clk->ops->unprepare)
> + clk->ops->unprepare(clk->hw);
> +
> + __clk_unprepare(clk->parent);
> +}
> +
> +void clk_unprepare(struct clk *clk)
> +{
> + mutex_lock(&prepare_lock);
> + __clk_unprepare(clk);
> + mutex_unlock(&prepare_lock);
> +}
> +EXPORT_SYMBOL_GPL(clk_unprepare);
> +
> +static int __clk_prepare(struct clk *clk)
> +{
> + int ret = 0;
> +
> + if (!clk)
> + return 0;
> +
> + if (clk->prepare_count == 0) {
> + ret = __clk_prepare(clk->parent);
> + if (ret)
> + return ret;
> +
> + if (clk->ops->prepare) {
> + ret = clk->ops->prepare(clk->hw);
> + if (ret) {
> + __clk_unprepare(clk->parent);
> + return ret;
> + }
> + }
> + }
> +
> + clk->prepare_count++;
> +
> + return 0;
> +}
> +
> +int clk_prepare(struct clk *clk)
> +{
> + int ret;
> +
> + mutex_lock(&prepare_lock);
> + ret = __clk_prepare(clk);
> + mutex_unlock(&prepare_lock);
> +
> + return ret;
> +}
> +EXPORT_SYMBOL_GPL(clk_prepare);
> +
> +static void __clk_disable(struct clk *clk)
> +{
> + if (!clk)
> + return;
> +
> + if (WARN_ON(clk->enable_count == 0))
> + return;
> +
> + if (--clk->enable_count > 0)
> + return;
> +
> + if (clk->ops->disable)
> + clk->ops->disable(clk->hw);
> + __clk_disable(clk->parent);
> +}
> +
> +void clk_disable(struct clk *clk)
> +{
> + unsigned long flags;
> +
> + spin_lock_irqsave(&enable_lock, flags);
> + __clk_disable(clk);
> + spin_unlock_irqrestore(&enable_lock, flags);
> +}
> +EXPORT_SYMBOL_GPL(clk_disable);
> +
> +static int __clk_enable(struct clk *clk)
> +{
> + int ret;
> +
> + if (!clk)
> + return 0;
> +
> + if (WARN_ON(clk->prepare_count == 0))
> + return -ESHUTDOWN;
> +
> +
> + if (clk->enable_count == 0) {
> + ret = __clk_enable(clk->parent);
> + if (ret)
> + return ret;
> +
> + if (clk->ops->enable) {
> + ret = clk->ops->enable(clk->hw);
> + if (ret) {
> + __clk_disable(clk->parent);
> + return ret;
> + }
> + }
> + }
> +
> + clk->enable_count++;
> + return 0;
> +}
> +
> +int clk_enable(struct clk *clk)
> +{
> + unsigned long flags;
> + int ret;
> +
> + spin_lock_irqsave(&enable_lock, flags);
> + ret = __clk_enable(clk);
> + spin_unlock_irqrestore(&enable_lock, flags);
> +
> + return ret;
> +}
> +EXPORT_SYMBOL_GPL(clk_enable);
> +
> +unsigned long clk_get_rate(struct clk *clk)
> +{
> + if (!clk)
> + return 0;
> + return clk->rate;
> +}
> +EXPORT_SYMBOL_GPL(clk_get_rate);
> +
> +long clk_round_rate(struct clk *clk, unsigned long rate)
> +{
> + if (clk && clk->ops->round_rate)
> + return clk->ops->round_rate(clk->hw, rate);
> + return rate;
> +}
> +EXPORT_SYMBOL_GPL(clk_round_rate);
> +
> +int clk_set_rate(struct clk *clk, unsigned long rate)
> +{
> + /* not yet implemented */
> + return -ENOSYS;
> +}
> +EXPORT_SYMBOL_GPL(clk_set_rate);
> +
> +struct clk *clk_get_parent(struct clk *clk)
> +{
> + if (!clk)
> + return NULL;
> +
> + return clk->parent;
> +}
> +EXPORT_SYMBOL_GPL(clk_get_parent);
> +
> +int clk_set_parent(struct clk *clk, struct clk *parent)
> +{
> + /* not yet implemented */
> + return -ENOSYS;
> +}
> +EXPORT_SYMBOL_GPL(clk_set_parent);
> +
> +struct clk *clk_register(const struct clk_hw_ops *ops, struct clk_hw *hw,
> + const char *name)
> +{
> + struct clk *clk;
> +
> + clk = kzalloc(sizeof(*clk), GFP_KERNEL);
> + if (!clk)
> + return NULL;
> +
> + INIT_HLIST_HEAD(&clk->children);
> + INIT_HLIST_NODE(&clk->child_node);
> +
> + clk->name = name;
> + clk->ops = ops;
> + clk->hw = hw;
> + hw->clk = clk;
> +
> + /* Query the hardware for parent and initial rate */
> +
> + if (clk->ops->get_parent)
> + /* We don't to lock against prepare/enable here, as
> + * the clock is not yet accessible from anywhere */
> + clk->parent = clk->ops->get_parent(clk->hw);
> +
> + if (clk->ops->recalc_rate)
> + clk->rate = clk->ops->recalc_rate(clk->hw);
Why not set it to parent's rate if recalc_rate is NULL?
> +
> +
> + return clk;
> +}
> +EXPORT_SYMBOL_GPL(clk_register);
> diff --git a/drivers/clk/clkdev.c b/drivers/clk/clkdev.c
> index 6db161f..e2a9719 100644
> --- a/drivers/clk/clkdev.c
> +++ b/drivers/clk/clkdev.c
> @@ -23,6 +23,13 @@
> static LIST_HEAD(clocks);
> static DEFINE_MUTEX(clocks_mutex);
>
> +/* For USE_COMMON_STRUCT_CLK, these are provided in clk.c, but not exported
> + * through other headers; we don't want them used anywhere but here. */
> +#ifdef CONFIG_USE_COMMON_STRUCT_CLK
> +extern int __clk_get(struct clk *clk);
> +extern void __clk_put(struct clk *clk);
> +#endif
> +
> /*
> * Find the correct struct clk for the device and connection ID.
> * We do slightly fuzzy matching here:
> diff --git a/include/linux/clk.h b/include/linux/clk.h
> index 1d37f42..d6ae10b 100644
> --- a/include/linux/clk.h
> +++ b/include/linux/clk.h
> @@ -3,6 +3,7 @@
> *
> * Copyright (C) 2004 ARM Limited.
> * Written by Deep Blue Solutions Limited.
> + * Copyright (c) 2010-2011 Jeremy Kerr <jeremy.kerr at canonical.com>
> *
> * 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
> @@ -11,17 +12,137 @@
> #ifndef __LINUX_CLK_H
> #define __LINUX_CLK_H
>
> +#include <linux/kernel.h>
> +#include <linux/errno.h>
> +
> struct device;
>
> -/*
> - * The base API.
> +struct clk;
> +
> +#ifdef CONFIG_GENERIC_CLK
> +
> +struct clk_hw {
> + struct clk *clk;
> +};
> +
> +/**
> + * struct clk_hw_ops - Callback operations for hardware clocks; these are to
> + * be provided by the clock implementation, and will be called by drivers
> + * through the clk_* API.
> + *
> + * @prepare: Prepare the clock for enabling. This must not return until
> + * the clock is fully prepared, and it's safe to call clk_enable.
> + * This callback is intended to allow clock implementations to
> + * do any initialisation that may sleep. Called with
> + * prepare_lock held.
> + *
> + * @unprepare: Release the clock from its prepared state. This will typically
> + * undo any work done in the @prepare callback. Called with
> + * prepare_lock held.
> + *
> + * @enable: Enable the clock atomically. This must not return until the
> + * clock is generating a valid clock signal, usable by consumer
> + * devices. Called with enable_lock held. This function must not
> + * sleep.
> + *
> + * @disable: Disable the clock atomically. Called with enable_lock held.
> + * This function must not sleep.
> + *
> + * @recalc_rate Recalculate the rate of this clock, by quering hardware
> + * and/or the clock's parent. Called with the global clock mutex
> + * held. Optional, but recommended - if this op is not set,
> + * clk_get_rate will return 0.
If a clock don't have any divider, recalc_rate may be NULL. In such case,
clk_get_rate should return parent's rate.
Thanks
Richard
> + *
> + * @get_parent Query the parent of this clock; for clocks with multiple
> + * possible parents, query the hardware for the current
> + * parent. Currently only called when the clock is first
> + * registered.
> + *
> + * The clk_enable/clk_disable and clk_prepare/clk_unprepare pairs allow
> + * implementations to split any work between atomic (enable) and sleepable
> + * (prepare) contexts. If a clock requires sleeping code to be turned on, this
> + * should be done in clk_prepare. Switching that will not sleep should be done
> + * in clk_enable.
> + *
> + * Typically, drivers will call clk_prepare when a clock may be needed later
> + * (eg. when a device is opened), and clk_enable when the clock is actually
> + * required (eg. from an interrupt). Note that clk_prepare *must* have been
> + * called before clk_enable.
> */
> +struct clk_hw_ops {
> + int (*prepare)(struct clk_hw *);
> + void (*unprepare)(struct clk_hw *);
> + int (*enable)(struct clk_hw *);
> + void (*disable)(struct clk_hw *);
> + unsigned long (*recalc_rate)(struct clk_hw *);
> + long (*round_rate)(struct clk_hw *, unsigned long);
> + struct clk * (*get_parent)(struct clk_hw *);
> +};
>
> +/**
> + * clk_prepare - prepare clock for atomic enabling.
> + *
> + * @clk: The clock to prepare
> + *
> + * Do any possibly sleeping initialisation on @clk, allowing the clock to be
> + * later enabled atomically (via clk_enable). This function may sleep.
> + */
> +int clk_prepare(struct clk *clk);
> +
> +/**
> + * clk_unprepare - release clock from prepared state
> + *
> + * @clk: The clock to release
> + *
> + * Do any (possibly sleeping) cleanup on clk. This function may sleep.
> + */
> +void clk_unprepare(struct clk *clk);
> +
> +/**
> + * clk_register - register and initialize a new clock
> + *
> + * @ops: ops for the new clock
> + * @hw: struct clk_hw to be passed to the ops of the new clock
> + * @name: name to use for the new clock
> + *
> + * Register a new clock with the clk subsystem. Returns either a
> + * struct clk for the new clock or a NULL pointer.
> + */
> +struct clk *clk_register(const struct clk_hw_ops *ops, struct clk_hw *hw,
> + const char *name);
> +
> +/**
> + * clk_unregister - remove a clock
> + *
> + * @clk: clock to unregister
> + *
> + * Remove a clock from the clk subsystem. This is currently not
> + * implemented but is provided to allow unregistration code to be
> + * written in drivers ready for use when an implementation is
> + * provided.
> + */
> +static inline int clk_unregister(struct clk *clk)
> +{
> + return -EOPNOTSUPP;
> +}
> +
> +#else /* !CONFIG_GENERIC_CLK */
>
> /*
> - * struct clk - an machine class defined object / cookie.
> + * For !CONFIG_GENERIC_CLK, we don't enforce any atomicity
> + * requirements for clk_enable/clk_disable, so the prepare and unprepare
> + * functions are no-ops
> */
> -struct clk;
> +static inline int clk_prepare(struct clk *clk) {
> + might_sleep();
> + return 0;
> +}
> +
> +static inline void clk_unprepare(struct clk *clk) {
> + might_sleep();
> +}
> +
> +#endif /* !CONFIG_GENERIC_CLK */
>
> /**
> * clk_get - lookup and obtain a reference to a clock producer.
> @@ -67,6 +188,7 @@ void clk_disable(struct clk *clk);
> /**
> * clk_get_rate - obtain the current clock rate (in Hz) for a clock source.
> * This is only valid once the clock source has been enabled.
> + * Returns zero if the clock rate is unknown.
> * @clk: clock source
> */
> unsigned long clk_get_rate(struct clk *clk);
> @@ -83,12 +205,6 @@ unsigned long clk_get_rate(struct clk *clk);
> */
> void clk_put(struct clk *clk);
>
> -
> -/*
> - * The remaining APIs are optional for machine class support.
> - */
> -
> -
> /**
> * clk_round_rate - adjust a rate to the exact rate a clock can provide
> * @clk: clock source
> @@ -97,7 +213,7 @@ void clk_put(struct clk *clk);
> * Returns rounded clock rate in Hz, or negative errno.
> */
> long clk_round_rate(struct clk *clk, unsigned long rate);
> -
> +
> /**
> * clk_set_rate - set the clock rate for a clock source
> * @clk: clock source
> @@ -106,7 +222,7 @@ long clk_round_rate(struct clk *clk, unsigned long rate);
> * Returns success (0) or negative errno.
> */
> int clk_set_rate(struct clk *clk, unsigned long rate);
> -
> +
> /**
> * clk_set_parent - set the parent clock source for this clock
> * @clk: clock source
> --
> 1.7.4.1
>
>
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