From mboxrd@z Thu Jan  1 00:00:00 1970
From: Uwe =?iso-8859-1?Q?Kleine-K=F6nig?=
Date: Wed, 09 Feb 2011 09:00:05 +0000
Subject: Re: [RFC,PATCH 1/3] Add a common struct clk
Message-Id: <20110209090005.GN27982@pengutronix.de>
List-Id: <linux-sh.vger.kernel.org>
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	<1297233693.242364.862698430999.1.gpush@pororo>
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To: linux-arm-kernel@lists.infradead.org

Hi Jeremy,

On Wed, Feb 09, 2011 at 02:41:33PM +0800, Jeremy Kerr wrote:
> 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.
>=20
> This change is an effort to unify struct clk where possible, by defining
> a common struct clk, containing 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.
>=20
> This allows us to share clock code among platforms, and makes it
> possible to dynamically create clock devices in platform-independent
> code.
>=20
> Platforms can enable the generic struct clock through
> CONFIG_USE_COMMON_STRUCT_CLK. In this case, the clock infrastructure
> consists of a common struct clk:
>=20
> struct clk {
> 	const struct clk_ops	*ops;
> 	unsigned int		enable_count;
> 	unsigned int		prepare_count;
> 	spinlock_t		enable_lock;
> 	struct mutex		prepare_lock;
> };
>=20
> And a set of clock operations (defined per type of clock):
>=20
> struct clk_ops {
> 	int             (*enable)(struct clk *);
> 	void            (*disable)(struct clk *);
> 	unsigned long   (*get_rate)(struct clk *);
> 	[...]
> };
>=20
> To define a hardware-specific clock, machine code can "subclass" the
> struct clock into a new struct (adding any device-specific data), and
> provide a set of operations:
>=20
> struct clk_foo {
> 	struct clk	clk;
> 	void __iomem	*some_register;
> };
>=20
> struct clk_ops clk_foo_ops =3D {
> 	.get_rate =3D clk_foo_get_rate,
> };
>=20
> The common clock definitions are based on a development patch from Ben
> Herrenschmidt <benh@kernel.crashing.org>.
>=20
> Signed-off-by: Jeremy Kerr <jeremy.kerr@canonical.com>
>=20
> ---
>  drivers/clk/Kconfig  |    3=20
>  drivers/clk/Makefile |    1=20
>  drivers/clk/clk.c    |  126 +++++++++++++++++++++++++++
>  include/linux/clk.h  |  194 +++++++++++++++++++++++++++++++++++++++++--
>  4 files changed, 315 insertions(+), 9 deletions(-)
>=20
> diff --git a/drivers/clk/Kconfig b/drivers/clk/Kconfig
> index 4168c88..6e3ae54 100644
> --- a/drivers/clk/Kconfig
> +++ b/drivers/clk/Kconfig
> @@ -2,3 +2,6 @@
>  config CLKDEV_LOOKUP
>  	bool
>  	select HAVE_CLK
> +
> +config USE_COMMON_STRUCT_CLK
> +	bool
> diff --git a/drivers/clk/Makefile b/drivers/clk/Makefile
> index 07613fa..a1a06d3 100644
> --- a/drivers/clk/Makefile
> +++ b/drivers/clk/Makefile
> @@ -1,2 +1,3 @@
> =20
>  obj-$(CONFIG_CLKDEV_LOOKUP)	+=3D clkdev.o
> +obj-$(CONFIG_USE_COMMON_STRUCT_CLK) +=3D clk.o
> diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
> new file mode 100644
> index 0000000..c35478a
> --- /dev/null
> +++ b/drivers/clk/clk.c
> @@ -0,0 +1,126 @@
> +/*
> + * Copyright (C) 2010-2011 Canonical Ltd <jeremy.kerr@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>
> +
> +int clk_prepare(struct clk *clk)
> +{
> +	int ret =3D 0;
> +
> +	mutex_lock(&clk->prepare_lock);
> +	if (clk->prepare_count =3D 0 && clk->ops->prepare)
> +		ret =3D clk->ops->prepare(clk);
> +
> +	if (!ret)
> +		clk->prepare_count++;
> +	mutex_unlock(&clk->prepare_lock);
> +
> +	return ret;
> +}
> +EXPORT_SYMBOL_GPL(clk_prepare);
> +
> +void clk_unprepare(struct clk *clk)
> +{
> +	mutex_lock(&clk->prepare_lock);
> +
> +	WARN_ON(clk->prepare_count =3D 0);
> +
> +	if (--clk->prepare_count =3D 0 && clk->ops->unprepare)
> +		clk->ops->unprepare(clk);
> +
> +	mutex_unlock(&clk->prepare_lock);
> +}
> +EXPORT_SYMBOL_GPL(clk_unprepare);
> +
> +int clk_enable(struct clk *clk)
> +{
> +	unsigned long flags;
> +	int ret =3D 0;
> +
> +	spin_lock_irqsave(&clk->enable_lock, flags);
> +	if (clk->enable_count =3D 0 && clk->ops->enable)
> +		ret =3D clk->ops->enable(clk);
> +
> +	if (!ret)
> +		clk->enable_count++;
> +	spin_unlock_irqrestore(&clk->enable_lock, flags);
> +
> +	return ret;
> +}
> +EXPORT_SYMBOL_GPL(clk_enable);
> +
> +void clk_disable(struct clk *clk)
> +{
> +	unsigned long flags;
> +
> +	spin_lock_irqsave(&clk->enable_lock, flags);
> +
> +	WARN_ON(clk->enable_count =3D 0);
> +
> +	if (!--clk->enable_count =3D 0 && clk->ops->disable)
s/!//

> +		clk->ops->disable(clk);
> +
> +	spin_unlock_irqrestore(&clk->enable_lock, flags);
> +}
> +EXPORT_SYMBOL_GPL(clk_disable);
> +
> +unsigned long clk_get_rate(struct clk *clk)
> +{
> +	if (clk->ops->get_rate)
> +		return clk->ops->get_rate(clk);
> +	return 0;
> +}
> +EXPORT_SYMBOL_GPL(clk_get_rate);
> +
> +long clk_round_rate(struct clk *clk, unsigned long rate)
> +{
> +	if (clk->ops->round_rate)
> +		return clk->ops->round_rate(clk, rate);
> +	return -ENOSYS;
> +}
> +EXPORT_SYMBOL_GPL(clk_round_rate);
> +
> +int clk_set_rate(struct clk *clk, unsigned long rate)
> +{
> +	if (clk->ops->set_rate)
> +		return clk->ops->set_rate(clk, rate);
> +	return -ENOSYS;
> +}
> +EXPORT_SYMBOL_GPL(clk_set_rate);
> +
> +int clk_set_parent(struct clk *clk, struct clk *parent)
> +{
> +	if (clk->ops->set_parent)
> +		return clk->ops->set_parent(clk, parent);
> +	return -ENOSYS;
> +}
> +EXPORT_SYMBOL_GPL(clk_set_parent);
> +
> +struct clk *clk_get_parent(struct clk *clk)
> +{
> +	if (clk->ops->get_parent)
> +		return clk->ops->get_parent(clk);
> +	return ERR_PTR(-ENOSYS);
> +}
> +EXPORT_SYMBOL_GPL(clk_get_parent);
> +
> +int __clk_get(struct clk *clk)
> +{
> +	if (clk->ops->get)
> +		return clk->ops->get(clk);
> +	return 1;
> +}
> +
> +void __clk_put(struct clk *clk)
> +{
> +	if (clk->ops->put)
> +		clk->ops->put(clk);
> +}
> diff --git a/include/linux/clk.h b/include/linux/clk.h
> index 1d37f42..fe806b7 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@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
> @@ -11,18 +12,198 @@
>  #ifndef __LINUX_CLK_H
>  #define __LINUX_CLK_H
> =20
> +#include <linux/err.h>
> +#include <linux/mutex.h>
> +#include <linux/spinlock.h>
> +
>  struct device;
> =20
> -/*
> - * The base API.
> +#ifdef CONFIG_USE_COMMON_STRUCT_CLK
> +
> +/* If we're using the common struct clk, we define the base clk object h=
ere */
> +
> +/**
> + * struct clk - hardware independent clock structure
> + * @ops:		implementation-specific ops for this clock
> + * @enable_count:	count of clk_enable() calls active on this clock
> + * @enable_lock:	lock for atomic enable
> + * @prepare_count:	count of clk_prepare() calls active on this clock
> + * @prepare_lock:	lock for sleepable prepare
> + *
> + * The base clock object, used by drivers for hardware-independent manip=
ulation
> + * of clock lines. This will be 'subclassed' by device-specific implemen=
tations,
> + * which add device-specific data to struct clk. For example:
> + *
> + *  struct clk_foo {
> + *      struct clk;
> + *      [device specific fields]
> + *  };
> + *
> + * The clock driver code will manage the device-specific data, and pass
> + * clk_foo.clk to the common clock code. The clock driver will be called
> + * through the @ops callbacks.
> + *
> + * The @enable_lock and @prepare_lock members are used to serialise acce=
sses
> + * to the ops->enable and ops->prepare functions (and the corresponding
> + * ops->disable and ops->unprepare functions).
> + */
> +struct clk {
> +	const struct clk_ops	*ops;
> +	unsigned int		enable_count;
> +	unsigned int		prepare_count;
> +	spinlock_t		enable_lock;
> +	struct mutex		prepare_lock;
> +};
> +
> +/* static initialiser for clocks */
> +#define INIT_CLK(name, o) {						\
> +	.ops		=3D &o,						\
> +	.enable_count	=3D 0,						\
> +	.prepare_count	=3D 0,						\
> +	.enable_lock	=3D __SPIN_LOCK_UNLOCKED(name.enable_lock),	\
> +	.prepare_lock	=3D __MUTEX_INITIALIZER(name.prepare_lock),	\
> +}
> +
> +/**
> + * struct clk_ops -  Callback operations for clocks; these are to be pro=
vided
> + * by the clock implementation, and will be called by drivers through th=
e 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 block. Called with
> + *		clk->prepare_lock held.
> + *
> + * @unprepare:	Release the clock from its prepared state. This will typi=
cally
> + *		undo any work done in the @prepare callback. Called with
> + *		clk->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 clk->enable_lock held. This function
> + *		must not sleep.
> + *
> + * @disable:	Disable the clock atomically. Called with clk->enable_lock =
held.
> + *		This function must not sleep.
> + *
> + * @get:	Called by the core clock code when a device driver acquires a
> + *		clock via clk_get(). Optional.
> + *
> + * @put:	Called by the core clock code when a devices driver releases a
> + *		clock via clk_put(). Optional.
> + *
> + * The clk_enable/clk_disable and clk_prepare/clk_unprepare pairs allow
> + * implementations to split any work between atomic (enable) and sleepab=
le
> + * (prepare) contexts.  If a clock requires blocking code to be turned o=
n, this
> + * should be done in clk_prepare. Switching that will not block should b=
e done
> + * in clk_enable.
> + *
> + * Typically, drivers will call clk_prepare when a clock may be needed l=
ater
> + * (eg. when a device is opened), and clk_enable when the clock is actua=
lly
> + * required (eg. from an interrupt). Note that clk_prepare *must* have b=
een
> + * called before clk_enable.
> + *
> + * For other callbacks, see the corresponding clk_* functions. Parameter=
s and
> + * return values are passed directly from/to these API functions, or
> + * -ENOSYS (or zero, in the case of clk_get_rate) is returned if the cal=
lback
> + * is NULL, see kernel/clk.c for implementation details. All are optiona=
l.
> + */
> +struct clk_ops {
> +	int		(*prepare)(struct clk *);
> +	void		(*unprepare)(struct clk *);
> +	int		(*enable)(struct clk *);
> +	void		(*disable)(struct clk *);
> +	int		(*get)(struct clk *);
> +	void		(*put)(struct clk *);
> +	unsigned long	(*get_rate)(struct clk *);
> +	long		(*round_rate)(struct clk *, unsigned long);
> +	int		(*set_rate)(struct clk *, unsigned long);
> +	int		(*set_parent)(struct clk *, struct clk *);
> +	struct clk *	(*get_parent)(struct clk *);
> +};
> +
> +/**
> + * __clk_get - acquire a reference to a clock
> + *
> + * @clk: The clock to refcount
> + *
> + * Before a clock is returned from clk_get, this function should be call=
ed
> + * to update any clock-specific refcounting.
> + *
> + * Returns non-zero on success, zero on failure.
> + *
> + * Drivers should not need this function, it is called by the common clo=
ck
> + * infrastructure.
> + */
> +int __clk_get(struct clk *clk);
> +
> +/**
> + * __clk_put - release reference to a clock
> + *
> + * @clk: The clock to release
> + *
> + * Called by clock infrastructure code to indicate that a clock consumer
> + * has released a clock, to update any clock-specific refcounting.
> + *
> + * Drivers should not need this function, it is called by the common clo=
ck
> + * infrastructure.
> + */
> +void __clk_put(struct clk *clk);
> +
> +/**
> + * clk_prepare - prepare clock for atomic enabling.
> + *
> + * @clk: The clock to prepare
> + *
> + * Do any blocking 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 (possbly blocking) cleanup on clk. This function may sleep.
s/possbly/possibly/

Best regards
Uwe

--=20
Pengutronix e.K.                           | Uwe Kleine-K=F6nig            |
Industrial Linux Solutions                 | http://www.pengutronix.de/  |