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Date:	Fri, 4 Jul 2008 13:04:46 +0400
From:	Dmitry Baryshkov <dbaryshkov@...il.com>
To:	Ben Dooks <ben-linux@...ff.org>
Cc:	linux-kernel@...r.kernel.org, akpm@...ux-foundation.org,
	Haavard Skinnemoen <haavard.skinnemoen@...el.com>,
	Russell King <rmk+lkml@....linux.org.uk>,
	Paul Mundt <lethal@...ux-sh.org>,
	pHilipp Zabel <philipp.zabel@...il.com>,
	Pavel Machek <pavel@....cz>, tony@...mide.com, paul@...an.com,
	David Brownell <david-b@...bell.net>,
	Mark Brown <broonie@...nsource.wolfsonmicro.com>,
	ian <spyro@....com>
Subject: Re: [PATCH 1/3] Clocklib: add generic framework for managing
	clocks.

On Thu, Jul 03, 2008 at 09:31:57PM +0100, Ben Dooks wrote:
> On Thu, Jun 26, 2008 at 04:51:38PM +0400, Dmitry Baryshkov wrote:
> > Provide a generic framework that platform may choose
> > to support clocks api. In particular this provides
> > platform-independant struct clk definition, a full
> > implementation of clocks api and a set of functions
> > for registering and unregistering clocks in a safe way.
> > 
> > Signed-off-by: Dmitry Baryshkov <dbaryshkov@...il.com>
> > ---
> >  include/linux/clocklib.h |   58 ++++++++
> >  lib/Kconfig              |    3 +
> >  lib/Makefile             |    1 +
> >  lib/clocklib.c           |  353 ++++++++++++++++++++++++++++++++++++++++++++++
> 
> why under lib? drivers/clk might be a better place for this.

Because there will be probably no "clock only" drivers. Probably it
should go into kernel/, but definitely not into drivers/clk/

> 
> >  4 files changed, 415 insertions(+), 0 deletions(-)
> >  create mode 100644 include/linux/clocklib.h
> >  create mode 100644 lib/clocklib.c
> > 
> > diff --git a/include/linux/clocklib.h b/include/linux/clocklib.h
> > new file mode 100644
> > index 0000000..cf2b41e
> > --- /dev/null
> > +++ b/include/linux/clocklib.h
> > @@ -0,0 +1,58 @@
> > +/*
> > + * Copyright (C) 2008 Dmitry Baryshkov
> > + *
> > + * This file is released under the GPL v2.
> > + */
> > +
> > +#ifndef CLKLIB_H
> > +#define CLKLIB_H
> > +
> > +#include <linux/spinlock.h>
> > +#include <linux/kref.h>
> > +
> > +struct clk;
> > +
> > +/**
> > + * struct clk_ops - generic clock management operations
> > + * @can_get: checks whether passed device can get this clock
> > + * @set_parent: reconfigures the clock to use specified parent
> > + * @set_mode: enable or disable specified clock
> > + * @get_rate: obtain the current clock rate of a specified clock
> > + * @set_rate: set the clock rate for a specified clock
> > + * @round_rate: adjust a reate to the exact rate a clock can provide
> > + *
> > + * This structure specifies clock operations that are used to configure
> > + * specific clock.
> > + */
> > +struct clk_ops {
> > +	int (*can_get)(struct clk *clk, struct device *dev);
> > +	int (*set_parent)(struct clk *clk, struct clk *parent);
> > +	int (*enable)(struct clk *clk);
> > +	void (*disable)(struct clk *clk);
> > +	unsigned long (*get_rate)(struct clk *clk);
> > +	long (*round_rate)(struct clk *clk, unsigned long hz, bool apply);
> > +};
> 
> 
> I'd much prefer to see the following changes:
> 
> 1) enable and disable merged into one, and pass an enable
>    parameter, ie:
> 
> 	int (*set_enable)(struct clk *clk, bool on);
> 
> as most code I see is of the following:
> 
> int myclk_enable(struct clk *clk, bool on)
> {
> 	clkbit = bit_for_clk(clk);
> 	reg = read_reg(reg_for_clk(clk));
> 	
> 	if (on)
> 		reg |= clkbit;
> 	else
> 		reg &= ~clkbit;
> 
> 	write_reg(reg, reg_for_clk(clk));
> 	return 0;
> }

It was discussed before. Andrew Morton specifically said, that he
doesn't want set_enable-like functions with bool param.

> whereas if you have seperate enable and disable methods you
> end up duplicating quite a lot of that code, as so:
> 
> int myclk_enable(struct clk *clk)
> {
> 	clkbit = bit_for_clk(clk);
> 	reg = read_reg(reg_for_clk(clk));
> 	
> 	reg |= clkbit;
> 
> 	write_reg(reg, reg_for_clk(clk));
> 	return 0;
> }
> 
> int myclk_disable(struct clk *clk)
> {
> 	clkbit = bit_for_clk(clk);
> 	reg = read_reg(reg_for_clk(clk));
> 	
> 	reg &= ~clkbit;
> 
> 	write_reg(reg, reg_for_clk(clk));
> 	return 0;
> }
> 
> > +
> > +
> > +struct clk {
> > +	struct list_head node;
> > +	spinlock_t *lock;
> > +	struct kref ref;
> > +	int usage;
> > +#ifdef CONFIG_DEBUG_FS
> > +	struct dentry *dir;
> > +	struct dentry *info;
> > +#endif
> 
> Can't you hide this in the code, say by wrappering the
> struct with something else when it is registered?

It is allocated dynamically by drivers. I can move this to
struct clk_private to specify that it's private, but it should be
visible outside

> 
> > +
> > +	const char *name;
> > +	struct clk *parent;
> > +	struct clk_ops *ops;
> > +	void (*release)(struct clk *clk);
> > +};
> > +
> > +int clk_register(struct clk *clk);
> > +void clk_unregister(struct clk *clk);
> > +int clks_register(struct clk **clk, size_t num);
> > +void clks_unregister(struct clk **clk, size_t num);
> > +
> > +#endif
> > diff --git a/lib/Kconfig b/lib/Kconfig
> > index 8cc8e87..592f5e1 100644
> > --- a/lib/Kconfig
> > +++ b/lib/Kconfig
> > @@ -13,6 +13,9 @@ config GENERIC_FIND_FIRST_BIT
> >  config GENERIC_FIND_NEXT_BIT
> >  	def_bool n
> >  
> > +config HAVE_CLOCKLIB
> > +	tristate
> > +
> >  config CRC_CCITT
> >  	tristate "CRC-CCITT functions"
> >  	help
> > diff --git a/lib/Makefile b/lib/Makefile
> > index 74b0cfb..cee74e1 100644
> > --- a/lib/Makefile
> > +++ b/lib/Makefile
> > @@ -37,6 +37,7 @@ obj-$(CONFIG_PLIST) += plist.o
> >  obj-$(CONFIG_DEBUG_PREEMPT) += smp_processor_id.o
> >  obj-$(CONFIG_DEBUG_LIST) += list_debug.o
> >  obj-$(CONFIG_DEBUG_OBJECTS) += debugobjects.o
> > +obj-$(CONFIG_HAVE_CLOCKLIB) += clocklib.o
> 
> why not call this CONFIG_GENERIC_CLK ?

it was modelled after CONFIG_HAVE_GPIO_LIB

>   
> >  ifneq ($(CONFIG_HAVE_DEC_LOCK),y)
> >    lib-y += dec_and_lock.o
> > diff --git a/lib/clocklib.c b/lib/clocklib.c
> > new file mode 100644
> > index 0000000..590a665
> > --- /dev/null
> > +++ b/lib/clocklib.c
> > @@ -0,0 +1,353 @@
> > +/*
> > + * Generic clocks API implementation
> > + *
> > + * Copyright (c) 2008 Dmitry Baryshkov
> > + *
> > + * This file is released under the GPL v2.
> > + */
> > +#include <linux/kernel.h>
> > +#include <linux/module.h>
> > +#include <linux/clk.h>
> > +#include <linux/clocklib.h>
> > +#include <linux/spinlock.h>
> > +
> > +static LIST_HEAD(clocks);
> > +static DEFINE_SPINLOCK(clocks_lock);
> > +
> > +#ifdef CONFIG_DEBUG_FS
> > +#include <linux/debugfs.h>
> > +#include <linux/seq_file.h>
> > +static struct dentry *clkdir;
> 
> possibly seperate the code out into a seperate file

fine

> 
> > +
> > +static int clocklib_show(struct seq_file *s, void *data)
> > +{
> > +	struct clk *clk = s->private;
> > +
> > +	BUG_ON(!clk);
> > +
> > +	seq_printf(s, "set_parent=%savailable\nusage=%d/%d\nrate=%10lu Hz\n",
> > +			clk->ops && clk->ops->set_parent ? "not " : "",
> > +			clk->usage, atomic_read(&clk->ref.refcount),
> > +			clk_get_rate(clk));
> > +//	if (clk->ops && clk->ops->format)
> > +//			clk->ops->format(clk, s);
> > +
> > +	return 0;
> > +}
> > +
> > +static int clocklib_open(struct inode *inode, struct file *file)
> > +{
> > +	return single_open(file, clocklib_show, inode->i_private);
> > +}
> > +
> > +static struct file_operations clocklib_operations = {
> > +	.open		= clocklib_open,
> > +	.read		= seq_read,
> > +	.llseek		= seq_lseek,
> > +	.release	= single_release,
> > +};
> > +
> > +static int clk_debugfs_init(struct clk *clk)
> > +{
> > +	struct dentry *dir;
> > +	struct dentry *info;
> > +
> > +	if (!clkdir)
> > +		dump_stack();
> > +
> > +	dir = debugfs_create_dir(clk->name,
> > +			clk->parent ? clk->parent->dir : clkdir);
> > +
> > +	if (IS_ERR(dir))
> > +		return PTR_ERR(dir);
> > +
> > +	info = debugfs_create_file("info", S_IFREG | S_IRUGO,
> > +			dir, clk, &clocklib_operations);
> > +
> > +	if (IS_ERR(info)) {
> > +		debugfs_remove(dir);
> > +		return PTR_ERR(info);
> > +	}
> > +
> > +	clk->dir = dir;
> > +	clk->info = info;
> > +
> > +	return 0;
> > +}
> > +
> > +static void clk_debugfs_clean(struct clk *clk)
> > +{
> > +	if (clk->info)
> > +		debugfs_remove(clk->info);
> > +	clk->info = NULL;
> > +
> > +	if (clk->dir)
> > +		debugfs_remove(clk->dir);
> > +	clk->dir = NULL;
> > +}
> > +
> > +static void clk_debugfs_reparent(struct clk *clk, struct clk *old, struct clk *new)
> > +{
> > +	struct dentry *oldd = old ? old->dir : clkdir;
> > +	struct dentry *newd = new ? new->dir : clkdir;
> > +	struct dentry *dir = debugfs_rename(oldd, clk->dir, newd, clk->name);
> > +
> > +	if (IS_ERR(dir))
> > +		WARN_ON(1);
> > +	else
> > +		clk->dir = dir;
> > +}
> > +
> > +static int __init clocklib_debugfs_init(void)
> > +{
> > +	clkdir = debugfs_create_dir("clocks", NULL);
> > +	return 0;
> > +}
> > +core_initcall(clocklib_debugfs_init);
> > +#else
> > +#define clk_debugfs_init(clk) ({0;})
> > +#define clk_debugfs_clean(clk) do {} while (0);
> > +#define clk_debugfs_reparent(clk, old, new) do {} while (0);
> > +#endif
> > +
> > +static int clk_can_get_def(struct clk *clk, struct device *dev)
> > +{
> > +	return 1;
> > +}
> > +
> > +static unsigned long clk_get_rate_def(struct clk *clk)
> > +{
> > +	return 0;
> > +}
> > +
> > +static long clk_round_rate_def(struct clk *clk, unsigned long hz, bool apply)
> > +{
> > +	long rate = clk->ops->get_rate(clk);
> > +
> > +	if (apply && hz != rate)
> > +		return -EINVAL;
> > +
> > +	return rate;
> > +}
> > +
> > +static void clk_release(struct kref *ref)
> > +{
> > +	struct clk *clk = container_of(ref, struct clk, ref);
> > +
> > +	BUG_ON(!clk->release);
> > +
> > +	if (clk->parent)
> > +		kref_get(&clk->parent->ref);
> > +
> > +	clk->release(clk);
> > +}
> > +EXPORT_SYMBOL(clk_round_rate);
> > +
> > +struct clk* clk_get_parent(struct clk *clk)
> > +{
> > +	struct clk *parent;
> > +
> > +	spin_lock(clk->lock);
> > +
> > +	parent = clk->parent;
> > +	kref_get(&parent->ref);
> > +
> > +	spin_unlock(clk->lock);
> > +
> > +	return parent;
> > +}
> > +EXPORT_SYMBOL(clk_get_parent);
> > +
> > +int clk_set_parent(struct clk *clk, struct clk *parent)
> > +{
> > +	int rc = -EINVAL;
> > +	struct clk *old;
> > +
> > +	spin_lock(clk->lock);
> > +
> > +	if (!clk->ops->set_parent)
> > +		goto out;
> > +
> > +	old = clk->parent;
> > +
> > +	rc = clk->ops->set_parent(clk, parent);
> > +	if (rc)
> > +		goto out;
> > +
> > +	kref_get(&parent->ref);
> > +	clk->parent = parent;
> > +
> > +	clk_debugfs_reparent(clk, old, parent);
> > +
> > +	kref_put(&old->ref, clk_release);
> > +
> > +out:
> > +	spin_unlock(clk->lock);
> > +
> > +	return rc;
> > +}
> > +EXPORT_SYMBOL(clk_set_parent);
> > +
> > +int clk_register(struct clk *clk)
> > +{
> > +	int rc;
> > +
> > +	BUG_ON(!clk->ops);
> > +	BUG_ON(!clk->ops->enable || !clk->ops->disable);
> > +
> > +	if (!clk->ops->can_get)
> > +		clk->ops->can_get = clk_can_get_def;
> > +	if (!clk->ops->get_rate)
> > +		clk->ops->get_rate = clk_get_rate_def;
> > +	if (!clk->ops->round_rate)
> > +		clk->ops->round_rate = clk_round_rate_def;
> > +
> > +	kref_init(&clk->ref);
> > +
> > +	spin_lock(&clocks_lock);
> > +	if (clk->parent)
> > +		kref_get(&clk->parent->ref);
> > +	list_add_tail(&clk->node, &clocks);
> > +
> > +	rc = clk_debugfs_init(clk);
> > +	if (rc) {
> > +		list_del(&clk->node);
> > +		kref_put(&clk->ref, clk_release);
> > +	}
> > +
> > +	spin_unlock(&clocks_lock);
> > +
> > +	return 0;
> > +}
> > +EXPORT_SYMBOL(clk_register);
> > +
> > +void clk_unregister(struct clk *clk)
> > +{
> > +	spin_lock(&clocks_lock);
> > +	clk_debugfs_clean(clk);
> > +	list_del(&clk->node);
> > +	kref_put(&clk->ref, clk_release);
> > +	spin_unlock(&clocks_lock);
> > +}
> > +EXPORT_SYMBOL(clk_unregister);
> > +
> > +int clks_register(struct clk **clk, size_t num)
> > +{
> > +	int i;
> > +	int rc;
> > +	for (i = 0; i < num; i++) {
> > +		rc = clk_register(clk[i]);
> > +		if (rc)
> > +			return rc;
> > +	}
> > +
> > +	return 0;
> > +}
> > +EXPORT_SYMBOL(clks_register);
> > +
> > +void clks_unregister(struct clk **clk, size_t num)
> > +{
> > +	int i;
> > +	for (i = 0; i < num; i++)
> > +		clk_unregister(clk[i]);
> > +}
> > +EXPORT_SYMBOL(clks_unregister);
> > +
> > +struct clk *clk_get(struct device *dev, const char *id)
> > +{
> > +	struct clk *clk = NULL, *p;
> > +
> > +	spin_lock(&clocks_lock);
> > +	list_for_each_entry(p, &clocks, node)
> > +		if (strcmp(id, p->name) == 0 && p->ops->can_get(p, dev)) {
> > +			clk = p;
> > +			kref_get(&clk->ref);
> > +			break;
> > +		}
> > +
> > +	spin_unlock(&clocks_lock);
> > +
> > +	return clk;
> > +}
> > +EXPORT_SYMBOL(clk_get);
> > +
> > +void clk_put(struct clk *clk)
> > +{
> > +	kref_put(&clk->ref, clk_release);
> > +}
> > +EXPORT_SYMBOL(clk_put);
> > +
> > +int clk_enable(struct clk *clk)
> > +{
> > +	int rc = 0;
> > +
> > +	spin_lock(clk->lock);
> > +
> > +	clk->usage++;
> > +	if (clk->usage == 1)
> > +		rc = clk->ops->enable(clk);
> > +
> > +	if (rc)
> > +		clk->usage--;
> 
> clk->usage = 0; is the same, maybe also easier to encase
> the whole lot in the same if block:
> 
> 	if (clk->usage == 1) {
> 		rc = clk->ops->enable(clk);
> 
> 		if (rc)
> 			clk->usage = 0;
> 	}

ok

> 
> > +
> > +	spin_unlock(clk->lock);
> > +
> > +	return rc;
> > +}
> > +EXPORT_SYMBOL(clk_enable);
> > +
> > +void clk_disable(struct clk *clk)
> > +{
> > +	spin_lock(clk->lock);
> > +
> > +	WARN_ON(clk->usage <= 0);
> > +
> > +	clk->usage--;
> > +	if (clk->usage == 0)
> > +		clk->ops->disable(clk);
> > +
> > +	spin_unlock(clk->lock);
> > +}
> > +EXPORT_SYMBOL(clk_disable);
> > +
> > +unsigned long clk_get_rate(struct clk *clk)
> > +{
> > +	unsigned long hz;
> > +
> > +	spin_lock(clk->lock);
> > +
> > +	hz = clk->ops->get_rate(clk);
> > +
> > +	spin_unlock(clk->lock);
> > +
> > +	return hz;
> > +}
> > +EXPORT_SYMBOL(clk_get_rate);
> > +
> > +int clk_set_rate(struct clk *clk, unsigned long hz)
> > +{
> > +	long rc;
> > +
> > +	spin_lock(clk->lock);
> > +
> > +	rc = clk->ops->round_rate(clk, hz, 1);
> > +
> > +	spin_unlock(clk->lock);
> > +
> > +	return rc < 0 ? rc : 0;
> > +}
> > +EXPORT_SYMBOL(clk_set_rate);
> > +
> > +long clk_round_rate(struct clk *clk, unsigned long hz)
> > +{
> > +	long rc;
> > +
> > +	spin_lock(clk->lock);
> > +
> > +	rc = clk->ops->round_rate(clk, hz, 0);
> > +
> > +	spin_unlock(clk->lock);
> > +
> > +	return rc;
> > +}
> 
> -- 
> Ben (ben@...ff.org, http://www.fluff.org/)
> 
>   'a smiley only costs 4 bytes'

-- 
With best wishes
Dmitry

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