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Date:	Fri, 3 Oct 2014 16:15:15 -0700
From:	Stephen Boyd <sboyd@...eaurora.org>
To:	Tomeu Vizoso <tomeu.vizoso@...labora.com>
Cc:	Russell King <linux@....linux.org.uk>,
	Mike Turquette <mturquette@...aro.org>,
	Paul Walmsley <paul@...an.com>,
	Tony Lindgren <tony@...mide.com>, linux-omap@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	Javier Martinez Canillas <javier.martinez@...labora.co.uk>
Subject: Re: [PATCH 1/2] clk: Make clk API return per-user struct clk
 instances

On 10/02, Tomeu Vizoso wrote:
> Moves clock state to struct clk_core, but takes care to change as little API as
> possible.
> 
> struct clk_hw still has a pointer to a struct clk, which is the
> implementation's per-user clk instance, for backwards compatibility.
> 
> The struct clk that clk_get_parent() returns isn't owned by the caller, but by
> the clock implementation, so the former shouldn't call clk_put() on it.
> 
> Because some boards in mach-omap2 still register clocks statically, their clock
> registration had to be updated to take into account that the clock information
> is stored in struct clk_core now.
> 
> Signed-off-by: Tomeu Vizoso <tomeu.vizoso@...labora.com>
> ---


We should s/provider/core/ when we're dealing with clk_core
structures in the function signature. The providers are hardware
drivers and the core structures are for the framework, not the
same. Furthermore, the provider drivers should only be dealing
with clk_hw structures. The only place that clk_core should be in
clk-provider.h is in struct clk_hw because there's no way to get
around it.

This way, provider drivers should only be including
clk-provider.h because they only care about dealing with struct
clk_hw. Consumers should only be including linux/clk.h where they
only know about struct clk as an opaque pointer. Once we get OMAP
to stop using clk-private.h we can kill off that header entirely
(I see there are some other bogus users of that header outside of
OMAP that we should nuke). Then the framework can include
clk-provider.h and clk.h to map between the hw cookie and the
consumer cookie.

This is the end goal. I understand that the provider API is sort
of a mess with us allowing drivers to use the underscore and
non-underscore functions and the mixture of struct clk and struct
ckl_hw throughout.

 struct clk_hw <--> struct clk_core <----> struct clk
 				       \-> struct clk
 				       |-> struct clk

 providers
 ---------
 struct clk_hw {
 	struct clk_core *
	...
 };

 consumers
 ---------

 struct clk;

 hidden in core framework
 ------------------------
 struct clk {
 	struct clk_core *;
	...
 }

 struct clk_core {
 	struct clk_hw *;
	...
 }


> 
> diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
> index 4eeb8de..b216b13 100644
> --- a/drivers/clk/clk.c
> +++ b/drivers/clk/clk.c
> @@ -37,6 +37,13 @@ static HLIST_HEAD(clk_root_list);
>  static HLIST_HEAD(clk_orphan_list);
>  static LIST_HEAD(clk_notifier_list);
>  
> +static void clk_provider_put(struct clk_core *clk);

Does this need to be forward declared?

> +static long clk_provider_get_accuracy(struct clk_core *clk);
> +static bool clk_provider_is_prepared(struct clk_core *clk);
> +static bool clk_provider_is_enabled(struct clk_core *clk);
> +static long clk_provider_round_rate(struct clk_core *clk, unsigned long rate);
> @@ -356,7 +363,7 @@ out:
>   *
>   * Caller must hold prepare_lock.
>   */
> -static void clk_debug_unregister(struct clk *clk)
> +static void clk_debug_unregister(struct clk_core *clk)
>  {
>  	debugfs_remove_recursive(clk->dentry);
>  }
> @@ -366,8 +373,8 @@ struct dentry *clk_debugfs_add_file(struct clk *clk, char *name, umode_t mode,

We should pass struct clk_hw here instead of struct clk. Let's do
it soon before we get any users.

>  {
>  	struct dentry *d = NULL;
>  
> -	if (clk->dentry)
> -		d = debugfs_create_file(name, mode, clk->dentry, data, fops);
> +	if (clk->core->dentry)
> +		d = debugfs_create_file(name, mode, clk->core->dentry, data, fops);
>  
>  	return d;
>  }
> @@ -545,53 +553,67 @@ late_initcall_sync(clk_disable_unused);
>  
>  const char *__clk_get_name(struct clk *clk)
>  {
> -	return !clk ? NULL : clk->name;
> +	return !clk ? NULL : clk->core->name;
>  }
>  EXPORT_SYMBOL_GPL(__clk_get_name);
>  
>  struct clk_hw *__clk_get_hw(struct clk *clk)
>  {
> -	return !clk ? NULL : clk->hw;
> +	return !clk ? NULL : clk->core->hw;
>  }
>  EXPORT_SYMBOL_GPL(__clk_get_hw);
>  
>  u8 __clk_get_num_parents(struct clk *clk)
>  {
> -	return !clk ? 0 : clk->num_parents;
> +	return !clk ? 0 : clk->core->num_parents;
>  }
>  EXPORT_SYMBOL_GPL(__clk_get_num_parents);
>  
>  struct clk *__clk_get_parent(struct clk *clk)
>  {
> -	return !clk ? NULL : clk->parent;
> +	/* TODO: Create a per-user clk and change callers to call clk_put */

More like replace all callers with a function that returns their
parent's hw pointer.

	struct clk_hw *clk_provider_get_parent(struct clk_hw *hw)


> +	return !clk ? NULL : clk->core->parent->hw->clk;
>  }
>  EXPORT_SYMBOL_GPL(__clk_get_parent);
>  
> -struct clk *clk_get_parent_by_index(struct clk *clk, u8 index)
> +static struct clk_core *clk_provider_get_parent_by_index(struct clk_core *clk,
> +							 u8 index)
>  {
>  	if (!clk || index >= clk->num_parents)
>  		return NULL;
>  	else if (!clk->parents)
> -		return __clk_lookup(clk->parent_names[index]);
> +		return clk_provider_lookup(clk->parent_names[index]);
>  	else if (!clk->parents[index])
>  		return clk->parents[index] =
> -			__clk_lookup(clk->parent_names[index]);
> +			clk_provider_lookup(clk->parent_names[index]);
>  	else
>  		return clk->parents[index];
>  }
> +
> +struct clk *clk_get_parent_by_index(struct clk *clk, u8 index)
> +{
> +	struct clk_core *parent;
> +
> +	parent = clk_provider_get_parent_by_index(clk->core, index);
> +	if (IS_ERR(parent))
> +		return (void *)parent;

What is this for? Does it actually happen that we have error
pointers here?

> +
> +	/* TODO: Create a per-user clk and change callers to call clk_put */
> +	return parent->hw->clk;
> +}
>  EXPORT_SYMBOL_GPL(clk_get_parent_by_index);
>  
>  unsigned int __clk_get_enable_count(struct clk *clk)
>  {
> -	return !clk ? 0 : clk->enable_count;
> +	return !clk ? 0 : clk->core->enable_count;
>  }
>  
>  unsigned int __clk_get_prepare_count(struct clk *clk)
>  {
> -	return !clk ? 0 : clk->prepare_count;
> +	return !clk ? 0 : clk->core->prepare_count;
>  }

This function isn't even used. Maybe we should remove it.

>  
> -unsigned long __clk_get_rate(struct clk *clk)
> +static unsigned long clk_provider_get_rate_nolock(struct clk_core *clk)
>  {
>  	unsigned long ret;
>  
> @@ -1612,11 +1722,11 @@ EXPORT_SYMBOL_GPL(clk_get_parent);
>   *
>   * For single-parent clocks without .get_parent, first check to see if the
>   * .parents array exists, and if so use it to avoid an expensive tree
> - * traversal.  If .parents does not exist then walk the tree with __clk_lookup.
> + * traversal.  If .parents does not exist then walk the tree with clk_provider_lookup.

Maybe just remove the function name entirely so we don't have to
keep updating something that's obvious from the code.

>   */
> -static struct clk *__clk_init_parent(struct clk *clk)
> +static struct clk_core *__clk_init_parent(struct clk_core *clk)
>  {
> -	struct clk *ret = NULL;
> +	struct clk_core *ret = NULL;
>  	u8 index;
>  
>  	/* handle the trivial cases */
> @@ -1626,7 +1736,7 @@ static struct clk *__clk_init_parent(struct clk *clk)
>  
>  	if (clk->num_parents == 1) {
>  		if (IS_ERR_OR_NULL(clk->parent))
> -			ret = clk->parent = __clk_lookup(clk->parent_names[0]);
> +			ret = clk->parent = clk_provider_lookup(clk->parent_names[0]);
>  		ret = clk->parent;
>  		goto out;
>  	}
> @@ -1640,7 +1750,7 @@ static struct clk *__clk_init_parent(struct clk *clk)
>  
>  	/*
>  	 * Do our best to cache parent clocks in clk->parents.  This prevents
> -	 * unnecessary and expensive calls to __clk_lookup.  We don't set
> +	 * unnecessary and expensive calls to clk_provider_lookup.  We don't set

Ditto.

>  	 * clk->parent here; that is done by the calling function
>  	 */
>  
> @@ -2306,7 +2438,7 @@ int clk_notifier_unregister(struct clk *clk, struct notifier_block *nb)
>  	if (cn->clk == clk) {
>  		ret = srcu_notifier_chain_unregister(&cn->notifier_head, nb);
>  
> -		clk->notifier_count--;
> +		clk->core->notifier_count--;
>  
>  		/* XXX the notifier code should handle this better */
>  		if (!cn->notifier_head.head) {
> @@ -2325,6 +2457,31 @@ int clk_notifier_unregister(struct clk *clk, struct notifier_block *nb)
>  }
>  EXPORT_SYMBOL_GPL(clk_notifier_unregister);
>  
> +struct clk *__clk_create_clk(struct clk_core *clk_core, const char *dev_id,

This should take clk_hw instead of clk_core.

> +			     const char *con_id)
> +{
> +	struct clk *clk;
> +
> +	/* This is to allow this function to be chained to others */
> +	if (!clk_core || IS_ERR(clk_core))
> +		return (struct clk *) clk_core;
> +
> +	clk = kzalloc(sizeof(*clk), GFP_KERNEL);
> +	if (!clk)
> +		return ERR_PTR(-ENOMEM);
> +
> +	clk->core = clk_core;
> +	clk->dev_id = dev_id;
> +	clk->con_id = con_id;
> +
> +	return clk;
> +}
> +
> +
>  #ifdef CONFIG_OF
>  /**
>   * struct of_clk_provider - Clock provider registration structure
> diff --git a/drivers/clk/clk.h b/drivers/clk/clk.h
> index c798138..4a17902 100644
> --- a/drivers/clk/clk.h
> +++ b/drivers/clk/clk.h
> @@ -9,9 +9,16 @@
>   * published by the Free Software Foundation.
>   */
>  
> +#include <linux/clk-private.h>

Ah, please no. Why do we need this?

> +
>  #if defined(CONFIG_OF) && defined(CONFIG_COMMON_CLK)

These ifdefs look useless.

>  struct clk *of_clk_get_by_clkspec(struct of_phandle_args *clkspec);
>  struct clk *__of_clk_get_from_provider(struct of_phandle_args *clkspec);
>  void of_clk_lock(void);
>  void of_clk_unlock(void);
>  #endif
> +
> +#if defined(CONFIG_COMMON_CLK)

So we shouldn't need this one either.

> +struct clk *__clk_create_clk(struct clk_core *clk_core, const char *dev_id,
> +			     const char *con_id);
> +#endif
> diff --git a/drivers/clk/clkdev.c b/drivers/clk/clkdev.c
> index da4bda8..fe3712f 100644
> --- a/drivers/clk/clkdev.c
> +++ b/drivers/clk/clkdev.c
> @@ -168,14 +172,27 @@ static struct clk_lookup *clk_find(const char *dev_id, const char *con_id)
>  struct clk *clk_get_sys(const char *dev_id, const char *con_id)
>  {
>  	struct clk_lookup *cl;
> +	struct clk *clk = NULL;
>  
>  	mutex_lock(&clocks_mutex);
>  	cl = clk_find(dev_id, con_id);
> -	if (cl && !__clk_get(cl->clk))
> -		cl = NULL;
> +	if (cl) {
> +#if defined(CONFIG_COMMON_CLK)
> +		clk = __clk_create_clk(cl->clk->core, dev_id, con_id);
> +		if (clk && !__clk_get(clk)) {
> +			kfree(clk);

This looks weird. It makes me suspect we've failed to reference
count something properly. Can we avoid this?

> +			clk = NULL;
> +		}
> +#else
> +		if (!__clk_get(cl->clk))
> +			cl = NULL;
> +		else
> +			clk = cl->clk;
> +#endif
> +	}
>  	mutex_unlock(&clocks_mutex);
>  
> -	return cl ? cl->clk : ERR_PTR(-ENOENT);
> +	return cl ? clk : ERR_PTR(-ENOENT);
>  }
>  EXPORT_SYMBOL(clk_get_sys);
>  
> diff --git a/include/linux/clk-provider.h b/include/linux/clk-provider.h
> index 411dd7e..8fd6320 100644
> --- a/include/linux/clk-provider.h
> +++ b/include/linux/clk-provider.h
> @@ -514,7 +519,7 @@ struct clk *clk_get_parent_by_index(struct clk *clk, u8 index);
>  unsigned int __clk_get_enable_count(struct clk *clk);
>  unsigned int __clk_get_prepare_count(struct clk *clk);
>  unsigned long __clk_get_rate(struct clk *clk);
> -unsigned long __clk_get_accuracy(struct clk *clk);
> +unsigned long __clk_get_accuracy(struct clk_core *clk);

Oops. Maybe we can just delete this one given that nobody uses it.

>  unsigned long __clk_get_flags(struct clk *clk);
>  bool __clk_is_prepared(struct clk *clk);
>  bool __clk_is_enabled(struct clk *clk);
> @@ -523,6 +528,22 @@ long __clk_mux_determine_rate(struct clk_hw *hw, unsigned long rate,
>  			      unsigned long *best_parent_rate,
>  			      struct clk **best_parent_p);
>  
> +unsigned long clk_provider_get_rate(struct clk_core *clk);
> +struct clk_core *clk_provider_get_parent(struct clk_core *clk);
> +
> +/**
> + * __clk_core_to_clk - return per-user clk
> + * @clk: struct clk_core for which we want a per-user clk
> + *
> + * Returns a per-user clock that is owned by its provider. The caller shall not
> + * call clk_get() on it.
> + *
> + * This function should be only needed by implementors of
> + * clk_ops.determine_rate() and should be dropped once all have moved to a
> + * variant that returns **clk_core instead.

Can we do that before this patch? And also move them to use **clk_hw instead?

> + */
> +struct clk *__clk_core_to_clk(struct clk_core *clk);
> +

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