[PATCH] arm: mxc: utilise usecount field in clock operations

[PATCH] arm: mxc: utilise usecount field in clock operations

[Amit Kucheria]

This patch fixes the clock refcounting when reparenting is used.

Boot-tested on imx51 babbage board.

Sascha pointed out a good explanation of refcounting here:
http://www.spinics.net/lists/arm-kernel/msg85879.html

Signed-off-by: Amit Kucheria <amit.kucheria@canonical.com>
---
 arch/arm/plat-mxc/clock.c |   37 +++++++++++++++++++++++++------------
 1 files changed, 25 insertions(+), 12 deletions(-)

diff --git a/arch/arm/plat-mxc/clock.c b/arch/arm/plat-mxc/clock.c
index 323ff8c..2ed3ab1 100644
--- a/arch/arm/plat-mxc/clock.c
+++ b/arch/arm/plat-mxc/clock.c
@@ -52,13 +52,14 @@ static void __clk_disable(struct clk *clk)
 {
 	if (clk == NULL || IS_ERR(clk))
 		return;
-
-	__clk_disable(clk->parent);
-	__clk_disable(clk->secondary);
-
 	WARN_ON(!clk->usecount);
-	if (!(--clk->usecount) && clk->disable)
-		clk->disable(clk);
+
+	if (!(--clk->usecount)) {
+		if (clk->disable)
+			clk->disable(clk);
+		__clk_disable(clk->parent);
+		__clk_disable(clk->secondary);
+	}
 }
 
 static int __clk_enable(struct clk *clk)
@@ -66,12 +67,13 @@ static int __clk_enable(struct clk *clk)
 	if (clk == NULL || IS_ERR(clk))
 		return -EINVAL;
 
-	__clk_enable(clk->parent);
-	__clk_enable(clk->secondary);
-
-	if (clk->usecount++ == 0 && clk->enable)
-		clk->enable(clk);
+	if (clk->usecount++ == 0) {
+		__clk_enable(clk->parent);
+		__clk_enable(clk->secondary);
 
+		if (clk->enable)
+			clk->enable(clk);
+	}
 	return 0;
 }
 
@@ -160,17 +162,28 @@ EXPORT_SYMBOL(clk_set_rate);
 int clk_set_parent(struct clk *clk, struct clk *parent)
 {
 	int ret = -EINVAL;
+	struct clk *old;
 
 	if (clk == NULL || IS_ERR(clk) || parent == NULL ||
 	    IS_ERR(parent) || clk->set_parent == NULL)
 		return ret;
 
+	if (clk->usecount)
+		clk_enable(parent);
+
 	mutex_lock(&clocks_mutex);
 	ret = clk->set_parent(clk, parent);
-	if (ret == 0)
+	if (ret == 0) {
+		old = clk->parent;
 		clk->parent = parent;
+	} else {
+		old = parent;
+	}
 	mutex_unlock(&clocks_mutex);
 
+	if (clk->usecount)
+		clk_disable(old);
+
 	return ret;
 }
 EXPORT_SYMBOL(clk_set_parent);
-- 
1.7.0.4

[PATCH] arm: mxc: utilise usecount field in clock operations

[Amit Kucheria]

clk->usecount can be used by platform code to check if a clock is active or
not.

Signed-off-by: Amit Kucheria <amit.kucheria@canonical.com>
---
 arch/arm/plat-mxc/clock.c |   37 ++++++++++++++++++++++++-------------
 1 files changed, 24 insertions(+), 13 deletions(-)

diff --git a/arch/arm/plat-mxc/clock.c b/arch/arm/plat-mxc/clock.c
index 323ff8c..c791f38 100644
--- a/arch/arm/plat-mxc/clock.c
+++ b/arch/arm/plat-mxc/clock.c
@@ -50,15 +50,15 @@ static DEFINE_MUTEX(clocks_mutex);
 
 static void __clk_disable(struct clk *clk)
 {
-	if (clk == NULL || IS_ERR(clk))
+	if (clk == NULL || IS_ERR(clk) || !clk->usecount)
 		return;
 
-	__clk_disable(clk->parent);
-	__clk_disable(clk->secondary);
-
-	WARN_ON(!clk->usecount);
-	if (!(--clk->usecount) && clk->disable)
-		clk->disable(clk);
+	if (!(--clk->usecount)) {
+		if (clk->disable)
+			clk->disable(clk);
+		__clk_disable(clk->parent);
+		__clk_disable(clk->secondary);
+	}
 }
 
 static int __clk_enable(struct clk *clk)
@@ -66,12 +66,13 @@ static int __clk_enable(struct clk *clk)
 	if (clk == NULL || IS_ERR(clk))
 		return -EINVAL;
 
-	__clk_enable(clk->parent);
-	__clk_enable(clk->secondary);
-
-	if (clk->usecount++ == 0 && clk->enable)
-		clk->enable(clk);
+	if (clk->usecount++ == 0) {
+		__clk_enable(clk->parent);
+		__clk_enable(clk->secondary);
 
+		if (clk->enable)
+			clk->enable(clk);
+	}
 	return 0;
 }
 
@@ -160,17 +161,27 @@ EXPORT_SYMBOL(clk_set_rate);
 int clk_set_parent(struct clk *clk, struct clk *parent)
 {
 	int ret = -EINVAL;
+	struct clk *prev_parent = clk->parent;
 
 	if (clk == NULL || IS_ERR(clk) || parent == NULL ||
 	    IS_ERR(parent) || clk->set_parent == NULL)
 		return ret;
 
+	if (clk->usecount != 0) {
+		clk_enable(parent);
+	}
+
 	mutex_lock(&clocks_mutex);
 	ret = clk->set_parent(clk, parent);
-	if (ret == 0)
+	if (ret == 0) {
 		clk->parent = parent;
+	}
 	mutex_unlock(&clocks_mutex);
 
+	if (clk->usecount != 0) {
+		clk_disable(prev_parent);
+	}
+
 	return ret;
 }
 EXPORT_SYMBOL(clk_set_parent);
-- 
1.7.0.4

[PATCH] arm: mxc: utilise usecount field in clock operations

[Baruch Siach]

Hi Amit,

On Wed, Apr 21, 2010 at 09:37:31PM +0300, Amit Kucheria wrote:
> clk->usecount can be used by platform code to check if a clock is active or
> not.
> 
> Signed-off-by: Amit Kucheria <amit.kucheria@canonical.com>
> ---
>  arch/arm/plat-mxc/clock.c |   37 ++++++++++++++++++++++++-------------
>  1 files changed, 24 insertions(+), 13 deletions(-)
> 
> diff --git a/arch/arm/plat-mxc/clock.c b/arch/arm/plat-mxc/clock.c
> index 323ff8c..c791f38 100644
> --- a/arch/arm/plat-mxc/clock.c
> +++ b/arch/arm/plat-mxc/clock.c

[snip]

> @@ -160,17 +161,27 @@ EXPORT_SYMBOL(clk_set_rate);
>  int clk_set_parent(struct clk *clk, struct clk *parent)
>  {
>  	int ret = -EINVAL;
> +	struct clk *prev_parent = clk->parent;
>  
>  	if (clk == NULL || IS_ERR(clk) || parent == NULL ||
>  	    IS_ERR(parent) || clk->set_parent == NULL)
>  		return ret;
>  
> +	if (clk->usecount != 0) {
> +		clk_enable(parent);
> +	}

Unnecessary braces here. See chapter 3 of Documentation/CodingStyle.

> +
>  	mutex_lock(&clocks_mutex);
>  	ret = clk->set_parent(clk, parent);
> -	if (ret == 0)
> +	if (ret == 0) {
>  		clk->parent = parent;
> +	}

Ditto

>  	mutex_unlock(&clocks_mutex);
>  
> +	if (clk->usecount != 0) {
> +		clk_disable(prev_parent);
> +	}

Ditto

> +
>  	return ret;
>  }
>  EXPORT_SYMBOL(clk_set_parent);
> -- 

baruch

-- 
                                                     ~. .~   Tk Open Systems
=}------------------------------------------------ooO--U--Ooo------------{=
   - baruch at tkos.co.il - tel: +972.2.679.5364, http://www.tkos.co.il -

[PATCH] arm: mxc: utilise usecount field in clock operations

[Sascha Hauer]

On Wed, Apr 21, 2010 at 09:37:31PM +0300, Amit Kucheria wrote:
> clk->usecount can be used by platform code to check if a clock is active or
> not.

The patch seems mostly fine but the commit log not. How about something like
'This patch fixes the clock refcounting when reparenting is used.'

A reference to

http://www.spinics.net/lists/arm-kernel/msg85879.html

might help aswell.

> 
> Signed-off-by: Amit Kucheria <amit.kucheria@canonical.com>
> ---
>  arch/arm/plat-mxc/clock.c |   37 ++++++++++++++++++++++++-------------
>  1 files changed, 24 insertions(+), 13 deletions(-)
> 
> diff --git a/arch/arm/plat-mxc/clock.c b/arch/arm/plat-mxc/clock.c
> index 323ff8c..c791f38 100644
> --- a/arch/arm/plat-mxc/clock.c
> +++ b/arch/arm/plat-mxc/clock.c
> @@ -50,15 +50,15 @@ static DEFINE_MUTEX(clocks_mutex);
>  
>  static void __clk_disable(struct clk *clk)
>  {
> -	if (clk == NULL || IS_ERR(clk))
> +	if (clk == NULL || IS_ERR(clk) || !clk->usecount)
>  		return;
>  
> -	__clk_disable(clk->parent);
> -	__clk_disable(clk->secondary);
> -
> -	WARN_ON(!clk->usecount);
> -	if (!(--clk->usecount) && clk->disable)
> -		clk->disable(clk);
> +	if (!(--clk->usecount)) {
> +		if (clk->disable)
> +			clk->disable(clk);
> +		__clk_disable(clk->parent);
> +		__clk_disable(clk->secondary);
> +	}
>  }
>  
>  static int __clk_enable(struct clk *clk)
> @@ -66,12 +66,13 @@ static int __clk_enable(struct clk *clk)
>  	if (clk == NULL || IS_ERR(clk))
>  		return -EINVAL;
>  
> -	__clk_enable(clk->parent);
> -	__clk_enable(clk->secondary);
> -
> -	if (clk->usecount++ == 0 && clk->enable)
> -		clk->enable(clk);
> +	if (clk->usecount++ == 0) {
> +		__clk_enable(clk->parent);
> +		__clk_enable(clk->secondary);
>  
> +		if (clk->enable)
> +			clk->enable(clk);
> +	}
>  	return 0;
>  }
>  
> @@ -160,17 +161,27 @@ EXPORT_SYMBOL(clk_set_rate);
>  int clk_set_parent(struct clk *clk, struct clk *parent)
>  {
>  	int ret = -EINVAL;
> +	struct clk *prev_parent = clk->parent;
>  
>  	if (clk == NULL || IS_ERR(clk) || parent == NULL ||
>  	    IS_ERR(parent) || clk->set_parent == NULL)
>  		return ret;
>  
> +	if (clk->usecount != 0) {
> +		clk_enable(parent);
> +	}
> +
>  	mutex_lock(&clocks_mutex);
>  	ret = clk->set_parent(clk, parent);
> -	if (ret == 0)
> +	if (ret == 0) {
>  		clk->parent = parent;
> +	}

Please remove this hunk. It does not change anything except violating
the coding style. Also, please remove unnecessary braces.

>  	mutex_unlock(&clocks_mutex);
>  
> +	if (clk->usecount != 0) {
> +		clk_disable(prev_parent);
> +	}
> +
>  	return ret;
>  }
>  EXPORT_SYMBOL(clk_set_parent);
> -- 
> 1.7.0.4
> 
> 

-- 
Pengutronix e.K.                           |                             |
Industrial Linux Solutions                 | http://www.pengutronix.de/  |
Peiner Str. 6-8, 31137 Hildesheim, Germany | Phone: +49-5121-206917-0    |
Amtsgericht Hildesheim, HRA 2686           | Fax:   +49-5121-206917-5555 |

[PATCH] arm: mxc: utilise usecount field in clock operations

[Amit Kucheria]

On 10 Apr 22, Sascha Hauer wrote:
> On Wed, Apr 21, 2010 at 09:37:31PM +0300, Amit Kucheria wrote:
> > clk->usecount can be used by platform code to check if a clock is active or
> > not.
> 
> The patch seems mostly fine but the commit log not. How about something like
> 'This patch fixes the clock refcounting when reparenting is used.'
> 
> A reference to
> 
> http://www.spinics.net/lists/arm-kernel/msg85879.html
> 
> might help aswell.

Interesting. I had no idea about this work. I was just resurrecting old
patches from January.

Will fix and resend.

/Amit

> > 
> > Signed-off-by: Amit Kucheria <amit.kucheria@canonical.com>
> > ---
> >  arch/arm/plat-mxc/clock.c |   37 ++++++++++++++++++++++++-------------
> >  1 files changed, 24 insertions(+), 13 deletions(-)
> > 
> > diff --git a/arch/arm/plat-mxc/clock.c b/arch/arm/plat-mxc/clock.c
> > index 323ff8c..c791f38 100644
> > --- a/arch/arm/plat-mxc/clock.c
> > +++ b/arch/arm/plat-mxc/clock.c
> > @@ -50,15 +50,15 @@ static DEFINE_MUTEX(clocks_mutex);
> >  
> >  static void __clk_disable(struct clk *clk)
> >  {
> > -	if (clk == NULL || IS_ERR(clk))
> > +	if (clk == NULL || IS_ERR(clk) || !clk->usecount)
> >  		return;
> >  
> > -	__clk_disable(clk->parent);
> > -	__clk_disable(clk->secondary);
> > -
> > -	WARN_ON(!clk->usecount);
> > -	if (!(--clk->usecount) && clk->disable)
> > -		clk->disable(clk);
> > +	if (!(--clk->usecount)) {
> > +		if (clk->disable)
> > +			clk->disable(clk);
> > +		__clk_disable(clk->parent);
> > +		__clk_disable(clk->secondary);
> > +	}
> >  }
> >  
> >  static int __clk_enable(struct clk *clk)
> > @@ -66,12 +66,13 @@ static int __clk_enable(struct clk *clk)
> >  	if (clk == NULL || IS_ERR(clk))
> >  		return -EINVAL;
> >  
> > -	__clk_enable(clk->parent);
> > -	__clk_enable(clk->secondary);
> > -
> > -	if (clk->usecount++ == 0 && clk->enable)
> > -		clk->enable(clk);
> > +	if (clk->usecount++ == 0) {
> > +		__clk_enable(clk->parent);
> > +		__clk_enable(clk->secondary);
> >  
> > +		if (clk->enable)
> > +			clk->enable(clk);
> > +	}
> >  	return 0;
> >  }
> >  
> > @@ -160,17 +161,27 @@ EXPORT_SYMBOL(clk_set_rate);
> >  int clk_set_parent(struct clk *clk, struct clk *parent)
> >  {
> >  	int ret = -EINVAL;
> > +	struct clk *prev_parent = clk->parent;
> >  
> >  	if (clk == NULL || IS_ERR(clk) || parent == NULL ||
> >  	    IS_ERR(parent) || clk->set_parent == NULL)
> >  		return ret;
> >  
> > +	if (clk->usecount != 0) {
> > +		clk_enable(parent);
> > +	}
> > +
> >  	mutex_lock(&clocks_mutex);
> >  	ret = clk->set_parent(clk, parent);
> > -	if (ret == 0)
> > +	if (ret == 0) {
> >  		clk->parent = parent;
> > +	}
> 
> Please remove this hunk. It does not change anything except violating
> the coding style. Also, please remove unnecessary braces.
> 
> >  	mutex_unlock(&clocks_mutex);
> >  
> > +	if (clk->usecount != 0) {
> > +		clk_disable(prev_parent);
> > +	}
> > +
> >  	return ret;
> >  }
> >  EXPORT_SYMBOL(clk_set_parent);
> > -- 
> > 1.7.0.4
> > 
> > 
> 
> -- 
> Pengutronix e.K.                           |                             |
> Industrial Linux Solutions                 | http://www.pengutronix.de/  |
> Peiner Str. 6-8, 31137 Hildesheim, Germany | Phone: +49-5121-206917-0    |
> Amtsgericht Hildesheim, HRA 2686           | Fax:   +49-5121-206917-5555 |

-- 
----------------------------------------------------------------------
Amit Kucheria, Kernel Engineer || amit.kucheria at canonical.com
----------------------------------------------------------------------

[PATCH] arm: mxc: utilise usecount field in clock operations

[Uwe Kleine-König]

On Wed, Apr 21, 2010 at 09:37:31PM +0300, Amit Kucheria wrote:
> clk->usecount can be used by platform code to check if a clock is active or
> not.
> 
> Signed-off-by: Amit Kucheria <amit.kucheria@canonical.com>
> ---
>  arch/arm/plat-mxc/clock.c |   37 ++++++++++++++++++++++++-------------
>  1 files changed, 24 insertions(+), 13 deletions(-)
> 
> diff --git a/arch/arm/plat-mxc/clock.c b/arch/arm/plat-mxc/clock.c
> index 323ff8c..c791f38 100644
> --- a/arch/arm/plat-mxc/clock.c
> +++ b/arch/arm/plat-mxc/clock.c
> @@ -50,15 +50,15 @@ static DEFINE_MUTEX(clocks_mutex);
>  
>  static void __clk_disable(struct clk *clk)
>  {
> -	if (clk == NULL || IS_ERR(clk))
> +	if (clk == NULL || IS_ERR(clk) || !clk->usecount)
>  		return;
>  
> -	__clk_disable(clk->parent);
> -	__clk_disable(clk->secondary);
> -
> -	WARN_ON(!clk->usecount);
> -	if (!(--clk->usecount) && clk->disable)
> -		clk->disable(clk);
> +	if (!(--clk->usecount)) {
> +		if (clk->disable)
> +			clk->disable(clk);
> +		__clk_disable(clk->parent);
> +		__clk_disable(clk->secondary);
> +	}
>  }
This removes the WARN_ON if the clock is already off.  Is this intended?

Best regards
Uwe

-- 
Pengutronix e.K.                           | Uwe Kleine-K?nig            |
Industrial Linux Solutions                 | http://www.pengutronix.de/  |