[2/2] clk: core: link consumer with clock driver
diff mbox series

Message ID 20181122212212.16039-3-miquel.raynal@bootlin.com
State New
Headers show
Series
  • Link consumer with clock driver
Related show

Commit Message

Miquel Raynal Nov. 22, 2018, 9:22 p.m. UTC
One major concern when, for instance, suspending/resuming a platform
is to never access registers before the underlying clock has been
resumed, otherwise most of the time the kernel will just crash. One
solution is to use syscore operations when registering clock drivers
suspend/resume callbacks. One problem of using syscore_ops is that the
suspend/resume scheduling will depend on the order of the
registrations, which brings (unacceptable) randomness in the process.

A feature called device links has been introduced to handle such
situation. It creates dependencies between consumers and providers,
enforcing e.g. the suspend/resume order when needed. Such feature is
already in use for regulators.

Add device links support in the clock subsystem by creating/deleting
the links at get/put time.

Example of a boot (ESPRESSObin, A3700 SoC) with devices linked to clocks:
ahci-mvebu d00e0000.sata: Linked as a consumer to d0013000.nb-periph-clk
mvneta d0030000.ethernet: Linked as a consumer to d0018000.sb-periph-clk
xhci-hcd d0058000.usb: Linked as a consumer to d0018000.sb-periph-clk
xenon-sdhci d00d0000.sdhci: Linked as a consumer to d0013000.nb-periph-clk
xenon-sdhci d00d0000.sdhci: Dropping the link to d0013000.nb-periph-clk
advk-pcie d0070000.pcie: Linked as a consumer to d0018000.sb-periph-clk
xenon-sdhci d00d0000.sdhci: Linked as a consumer to d0013000.nb-periph-clk
xenon-sdhci d00d0000.sdhci: Linked as a consumer to regulator.1
cpu cpu0: Linked as a consumer to d0013000.nb-periph-clk
cpu cpu0: Dropping the link to d0013000.nb-periph-clk
cpu cpu0: Linked as a consumer to d0013000.nb-periph-clk

Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
---
 drivers/clk/clk.c            | 20 ++++++++++++++++++++
 drivers/clk/clkdev.c         | 13 ++++++++++---
 include/linux/clk-provider.h |  2 ++
 3 files changed, 32 insertions(+), 3 deletions(-)

Comments

kernel test robot Nov. 23, 2018, 8:30 a.m. UTC | #1
Hi Miquel,

I love your patch! Yet something to improve:

[auto build test ERROR on clk/clk-next]
[also build test ERROR on v4.20-rc3 next-20181122]
[if your patch is applied to the wrong git tree, please drop us a note to help improve the system]

url:    https://github.com/0day-ci/linux/commits/Miquel-Raynal/Link-consumer-with-clock-driver/20181123-113833
base:   https://git.kernel.org/pub/scm/linux/kernel/git/clk/linux.git clk-next
config: sh-titan_defconfig (attached as .config)
compiler: sh4-linux-gnu-gcc (Debian 7.2.0-11) 7.2.0
reproduce:
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # save the attached .config to linux build tree
        GCC_VERSION=7.2.0 make.cross ARCH=sh 

All errors (new ones prefixed by >>):

   drivers//clk/clkdev.c: In function 'clk_get':
>> drivers//clk/clkdev.c:209:3: error: implicit declaration of function '__clk_device_link'; did you mean '__clk_free_clk'? [-Werror=implicit-function-declaration]
      __clk_device_link(dev, clk);
      ^~~~~~~~~~~~~~~~~
      __clk_free_clk
   drivers//clk/clkdev.c: In function 'clk_put':
>> drivers//clk/clkdev.c:217:2: error: implicit declaration of function '__clk_device_unlink'; did you mean 'device_online'? [-Werror=implicit-function-declaration]
     __clk_device_unlink(clk);
     ^~~~~~~~~~~~~~~~~~~
     device_online
   cc1: some warnings being treated as errors

vim +209 drivers//clk/clkdev.c

   193	
   194	struct clk *clk_get(struct device *dev, const char *con_id)
   195	{
   196		const char *dev_id = dev ? dev_name(dev) : NULL;
   197		struct clk *clk = NULL;
   198	
   199		if (dev && dev->of_node) {
   200			clk = __of_clk_get_by_name(dev->of_node, dev_id, con_id);
   201			if (PTR_ERR(clk) == -EPROBE_DEFER)
   202				return clk;
   203		}
   204	
   205		if (IS_ERR_OR_NULL(clk))
   206			clk = clk_get_sys(dev_id, con_id);
   207	
   208		if (!IS_ERR(clk))
 > 209			__clk_device_link(dev, clk);
   210	
   211		return clk;
   212	}
   213	EXPORT_SYMBOL(clk_get);
   214	
   215	void clk_put(struct clk *clk)
   216	{
 > 217		__clk_device_unlink(clk);
   218		__clk_put(clk);
   219	}
   220	EXPORT_SYMBOL(clk_put);
   221	

---
0-DAY kernel test infrastructure                Open Source Technology Center
https://lists.01.org/pipermail/kbuild-all                   Intel Corporation
Miquel Raynal Nov. 23, 2018, 9:11 a.m. UTC | #2
Hello,

kbuild test robot <lkp@intel.com> wrote on Fri, 23 Nov 2018 16:30:00
+0800:

> Hi Miquel,
> 
> I love your patch! Yet something to improve:
> 
> [auto build test ERROR on clk/clk-next]
> [also build test ERROR on v4.20-rc3 next-20181122]
> [if your patch is applied to the wrong git tree, please drop us a note to help improve the system]
> 
> url:    https://github.com/0day-ci/linux/commits/Miquel-Raynal/Link-consumer-with-clock-driver/20181123-113833
> base:   https://git.kernel.org/pub/scm/linux/kernel/git/clk/linux.git clk-next
> config: sh-titan_defconfig (attached as .config)
> compiler: sh4-linux-gnu-gcc (Debian 7.2.0-11) 7.2.0
> reproduce:
>         wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
>         chmod +x ~/bin/make.cross
>         # save the attached .config to linux build tree
>         GCC_VERSION=7.2.0 make.cross ARCH=sh 
> 
> All errors (new ones prefixed by >>):
> 
>    drivers//clk/clkdev.c: In function 'clk_get':
> >> drivers//clk/clkdev.c:209:3: error: implicit declaration of function '__clk_device_link'; did you mean '__clk_free_clk'? [-Werror=implicit-function-declaration]  
>       __clk_device_link(dev, clk);
>       ^~~~~~~~~~~~~~~~~
>       __clk_free_clk
>    drivers//clk/clkdev.c: In function 'clk_put':
> >> drivers//clk/clkdev.c:217:2: error: implicit declaration of function '__clk_device_unlink'; did you mean 'device_online'? [-Werror=implicit-function-declaration]  
>      __clk_device_unlink(clk);
>      ^~~~~~~~~~~~~~~~~~~
>      device_online
>    cc1: some warnings being treated as errors

I figured thanks to this report that this code won't compile with
architectures not compliant to the common clock framework. I see there
is the following block in clkdev.c.

#if defined(CONFIG_OF) && defined(CONFIG_COMMON_CLK)
#else
#endif

Would you agree with me adding dummy functions in the #else section
like:

static inline void __clk_device_link(struct device *consumer, struct clk *clk)
{
       return;
}

static inline void __clk_device_unlink(struct clk *clk)
{
       return;
}

Do you want me to also declare these functions in the #if section
(with the external keyword) to balance the above declarations?

Thanks for your input.
Miquèl

> 
> vim +209 drivers//clk/clkdev.c
> 
>    193	
>    194	struct clk *clk_get(struct device *dev, const char *con_id)
>    195	{
>    196		const char *dev_id = dev ? dev_name(dev) : NULL;
>    197		struct clk *clk = NULL;
>    198	
>    199		if (dev && dev->of_node) {
>    200			clk = __of_clk_get_by_name(dev->of_node, dev_id, con_id);
>    201			if (PTR_ERR(clk) == -EPROBE_DEFER)
>    202				return clk;
>    203		}
>    204	
>    205		if (IS_ERR_OR_NULL(clk))
>    206			clk = clk_get_sys(dev_id, con_id);
>    207	
>    208		if (!IS_ERR(clk))
>  > 209			__clk_device_link(dev, clk);  
>    210	
>    211		return clk;
>    212	}
>    213	EXPORT_SYMBOL(clk_get);
>    214	
>    215	void clk_put(struct clk *clk)
>    216	{
>  > 217		__clk_device_unlink(clk);  
>    218		__clk_put(clk);
>    219	}
>    220	EXPORT_SYMBOL(clk_put);
>    221	
> 
> ---
> 0-DAY kernel test infrastructure                Open Source Technology Center
> https://lists.01.org/pipermail/kbuild-all                   Intel Corporation
Maxime Ripard Nov. 27, 2018, 12:38 p.m. UTC | #3
Hi Miquel,

On Thu, Nov 22, 2018 at 10:22:12PM +0100, Miquel Raynal wrote:
> One major concern when, for instance, suspending/resuming a platform
> is to never access registers before the underlying clock has been
> resumed, otherwise most of the time the kernel will just crash. One
> solution is to use syscore operations when registering clock drivers
> suspend/resume callbacks. One problem of using syscore_ops is that the
> suspend/resume scheduling will depend on the order of the
> registrations, which brings (unacceptable) randomness in the process.
> 
> A feature called device links has been introduced to handle such
> situation. It creates dependencies between consumers and providers,
> enforcing e.g. the suspend/resume order when needed. Such feature is
> already in use for regulators.
> 
> Add device links support in the clock subsystem by creating/deleting
> the links at get/put time.
> 
> Example of a boot (ESPRESSObin, A3700 SoC) with devices linked to clocks:
> ahci-mvebu d00e0000.sata: Linked as a consumer to d0013000.nb-periph-clk
> mvneta d0030000.ethernet: Linked as a consumer to d0018000.sb-periph-clk
> xhci-hcd d0058000.usb: Linked as a consumer to d0018000.sb-periph-clk
> xenon-sdhci d00d0000.sdhci: Linked as a consumer to d0013000.nb-periph-clk
> xenon-sdhci d00d0000.sdhci: Dropping the link to d0013000.nb-periph-clk
> advk-pcie d0070000.pcie: Linked as a consumer to d0018000.sb-periph-clk
> xenon-sdhci d00d0000.sdhci: Linked as a consumer to d0013000.nb-periph-clk
> xenon-sdhci d00d0000.sdhci: Linked as a consumer to regulator.1
> cpu cpu0: Linked as a consumer to d0013000.nb-periph-clk
> cpu cpu0: Dropping the link to d0013000.nb-periph-clk
> cpu cpu0: Linked as a consumer to d0013000.nb-periph-clk
> 
> Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
> ---
>  drivers/clk/clk.c            | 20 ++++++++++++++++++++
>  drivers/clk/clkdev.c         | 13 ++++++++++---
>  include/linux/clk-provider.h |  2 ++
>  3 files changed, 32 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
> index b799347c5fd6..33a0f2b0533a 100644
> --- a/drivers/clk/clk.c
> +++ b/drivers/clk/clk.c
> @@ -90,6 +90,7 @@ struct clk {
>  	unsigned long max_rate;
>  	unsigned int exclusive_count;
>  	struct hlist_node clks_node;
> +	struct device_link *link;
>  };
>  
>  /***           runtime pm          ***/
> @@ -262,6 +263,25 @@ struct clk_hw *__clk_get_hw(struct clk *clk)
>  }
>  EXPORT_SYMBOL_GPL(__clk_get_hw);
>  
> +void __clk_device_link(struct device *consumer, struct clk *clk)
> +{
> +	if (!consumer || !clk || !clk->core)
> +		return;
> +
> +	clk->link = device_link_add(consumer, clk->core->dev,
> +				    DL_FLAG_STATELESS);
> +}
> +EXPORT_SYMBOL_GPL(__clk_device_link);
> +
> +void __clk_device_unlink(struct clk *clk)
> +{
> +	if (!clk || !clk->link)
> +		return;
> +
> +	device_link_del(clk->link);
> +}
> +EXPORT_SYMBOL_GPL(__clk_device_unlink);
> +
>  unsigned int clk_hw_get_num_parents(const struct clk_hw *hw)
>  {
>  	return hw->core->num_parents;
> diff --git a/drivers/clk/clkdev.c b/drivers/clk/clkdev.c
> index 9ab3db8b3988..fccfd4c01457 100644
> --- a/drivers/clk/clkdev.c
> +++ b/drivers/clk/clkdev.c
> @@ -194,20 +194,27 @@ EXPORT_SYMBOL(clk_get_sys);
>  struct clk *clk_get(struct device *dev, const char *con_id)
>  {
>  	const char *dev_id = dev ? dev_name(dev) : NULL;
> -	struct clk *clk;
> +	struct clk *clk = NULL;
>  
>  	if (dev && dev->of_node) {
>  		clk = __of_clk_get_by_name(dev->of_node, dev_id, con_id);
> -		if (!IS_ERR(clk) || PTR_ERR(clk) == -EPROBE_DEFER)
> +		if (PTR_ERR(clk) == -EPROBE_DEFER)
>  			return clk;
>  	}
>  
> -	return clk_get_sys(dev_id, con_id);
> +	if (IS_ERR_OR_NULL(clk))
> +		clk = clk_get_sys(dev_id, con_id);
> +
> +	if (!IS_ERR(clk))
> +		__clk_device_link(dev, clk);
> +
> +	return clk;

I think this doesn't address all the cases. In your case, where you
have one consumer that is not a clock, and one provider that is a
clock, it works just fine.

However, if you have clocks providers chained, for example with one
oscillator, a clock controller, and a device, the link will be created
between the device and the controller, but there will be no link
between the controller and the oscillator.

Adding a link in __clk_init_parent looks like it would address that
case.

Maxime
Miquel Raynal Nov. 29, 2018, 4:03 p.m. UTC | #4
Hi Maxime,

Maxime Ripard <maxime.ripard@bootlin.com> wrote on Tue, 27 Nov 2018
13:38:58 +0100:

> Hi Miquel,
> 
> On Thu, Nov 22, 2018 at 10:22:12PM +0100, Miquel Raynal wrote:
> > One major concern when, for instance, suspending/resuming a platform
> > is to never access registers before the underlying clock has been
> > resumed, otherwise most of the time the kernel will just crash. One
> > solution is to use syscore operations when registering clock drivers
> > suspend/resume callbacks. One problem of using syscore_ops is that the
> > suspend/resume scheduling will depend on the order of the
> > registrations, which brings (unacceptable) randomness in the process.
> > 
> > A feature called device links has been introduced to handle such
> > situation. It creates dependencies between consumers and providers,
> > enforcing e.g. the suspend/resume order when needed. Such feature is
> > already in use for regulators.
> > 
> > Add device links support in the clock subsystem by creating/deleting
> > the links at get/put time.
> > 
> > Example of a boot (ESPRESSObin, A3700 SoC) with devices linked to clocks:
> > ahci-mvebu d00e0000.sata: Linked as a consumer to d0013000.nb-periph-clk
> > mvneta d0030000.ethernet: Linked as a consumer to d0018000.sb-periph-clk
> > xhci-hcd d0058000.usb: Linked as a consumer to d0018000.sb-periph-clk
> > xenon-sdhci d00d0000.sdhci: Linked as a consumer to d0013000.nb-periph-clk
> > xenon-sdhci d00d0000.sdhci: Dropping the link to d0013000.nb-periph-clk
> > advk-pcie d0070000.pcie: Linked as a consumer to d0018000.sb-periph-clk
> > xenon-sdhci d00d0000.sdhci: Linked as a consumer to d0013000.nb-periph-clk
> > xenon-sdhci d00d0000.sdhci: Linked as a consumer to regulator.1
> > cpu cpu0: Linked as a consumer to d0013000.nb-periph-clk
> > cpu cpu0: Dropping the link to d0013000.nb-periph-clk
> > cpu cpu0: Linked as a consumer to d0013000.nb-periph-clk
> > 
> > Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
> > ---
> >  drivers/clk/clk.c            | 20 ++++++++++++++++++++
> >  drivers/clk/clkdev.c         | 13 ++++++++++---
> >  include/linux/clk-provider.h |  2 ++
> >  3 files changed, 32 insertions(+), 3 deletions(-)
> > 
> > diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
> > index b799347c5fd6..33a0f2b0533a 100644
> > --- a/drivers/clk/clk.c
> > +++ b/drivers/clk/clk.c
> > @@ -90,6 +90,7 @@ struct clk {
> >  	unsigned long max_rate;
> >  	unsigned int exclusive_count;
> >  	struct hlist_node clks_node;
> > +	struct device_link *link;
> >  };
> >  
> >  /***           runtime pm          ***/
> > @@ -262,6 +263,25 @@ struct clk_hw *__clk_get_hw(struct clk *clk)
> >  }
> >  EXPORT_SYMBOL_GPL(__clk_get_hw);
> >  
> > +void __clk_device_link(struct device *consumer, struct clk *clk)
> > +{
> > +	if (!consumer || !clk || !clk->core)
> > +		return;
> > +
> > +	clk->link = device_link_add(consumer, clk->core->dev,
> > +				    DL_FLAG_STATELESS);
> > +}
> > +EXPORT_SYMBOL_GPL(__clk_device_link);
> > +
> > +void __clk_device_unlink(struct clk *clk)
> > +{
> > +	if (!clk || !clk->link)
> > +		return;
> > +
> > +	device_link_del(clk->link);
> > +}
> > +EXPORT_SYMBOL_GPL(__clk_device_unlink);
> > +
> >  unsigned int clk_hw_get_num_parents(const struct clk_hw *hw)
> >  {
> >  	return hw->core->num_parents;
> > diff --git a/drivers/clk/clkdev.c b/drivers/clk/clkdev.c
> > index 9ab3db8b3988..fccfd4c01457 100644
> > --- a/drivers/clk/clkdev.c
> > +++ b/drivers/clk/clkdev.c
> > @@ -194,20 +194,27 @@ EXPORT_SYMBOL(clk_get_sys);
> >  struct clk *clk_get(struct device *dev, const char *con_id)
> >  {
> >  	const char *dev_id = dev ? dev_name(dev) : NULL;
> > -	struct clk *clk;
> > +	struct clk *clk = NULL;
> >  
> >  	if (dev && dev->of_node) {
> >  		clk = __of_clk_get_by_name(dev->of_node, dev_id, con_id);
> > -		if (!IS_ERR(clk) || PTR_ERR(clk) == -EPROBE_DEFER)
> > +		if (PTR_ERR(clk) == -EPROBE_DEFER)
> >  			return clk;
> >  	}
> >  
> > -	return clk_get_sys(dev_id, con_id);
> > +	if (IS_ERR_OR_NULL(clk))
> > +		clk = clk_get_sys(dev_id, con_id);
> > +
> > +	if (!IS_ERR(clk))
> > +		__clk_device_link(dev, clk);
> > +
> > +	return clk;  
> 
> I think this doesn't address all the cases. In your case, where you
> have one consumer that is not a clock, and one provider that is a
> clock, it works just fine.
> 
> However, if you have clocks providers chained, for example with one
> oscillator, a clock controller, and a device, the link will be created
> between the device and the controller, but there will be no link
> between the controller and the oscillator.

Indeed, there is not clock_get() in this case so you are right, a link
is missing if we want to track dependencies between clocks.

> 
> Adding a link in __clk_init_parent looks like it would address that
> case.

I will add one, thanks for the pointer.

> 
> Maxime
> 

I think device links must be managed in the following situations:
* A device gets a clock -> add a link between the device and the clock,
  save it in 'struct clk'.
* A device puts a clock -> remove the above link.
* A clock gets registered -> link the core clock with the parent core
  clock.
* A clock gets reparentized -> remove the above link and if there is a
  new parent, link the core clock to the parent core clock.
* A clock gets deregistered -> remove the link with the parent core
  clock if any and remove the link with each child clock if any (this
  will be done automatically because each child will get reparentized
  first).

I assume that a clock getting deregistered is not an input source for
any device anymore and thus there is already no more link to destroy on
this regard.


Thanks,
Miquèl
Stephen Boyd Nov. 30, 2018, 9:26 a.m. UTC | #5
Quoting Miquel Raynal (2018-11-23 01:11:32)
> Would you agree with me adding dummy functions in the #else section
> like:
> 
> static inline void __clk_device_link(struct device *consumer, struct clk *clk)
> {
>        return;
> }
> 
> static inline void __clk_device_unlink(struct clk *clk)
> {
>        return;
> }
> 
> Do you want me to also declare these functions in the #if section
> (with the external keyword) to balance the above declarations?

Why can't we do the linking in __clk_get() and __clk_put()?
Miquel Raynal Nov. 30, 2018, 10:20 a.m. UTC | #6
Hi Stephen,

Stephen Boyd <sboyd@kernel.org> wrote on Fri, 30 Nov 2018 01:26:20
-0800:

> Quoting Miquel Raynal (2018-11-23 01:11:32)
> > Would you agree with me adding dummy functions in the #else section
> > like:
> > 
> > static inline void __clk_device_link(struct device *consumer, struct clk *clk)
> > {
> >        return;
> > }
> > 
> > static inline void __clk_device_unlink(struct clk *clk)
> > {
> >        return;
> > }
> > 
> > Do you want me to also declare these functions in the #if section
> > (with the external keyword) to balance the above declarations?  
> 
> Why can't we do the linking in __clk_get() and __clk_put()?
> 

Because we need the caller's 'struct device' to make the link and
this is not available in __clk_get(). I tried to ad it as parameter but
I don't think it is possible to retrieve a 'struct device' from the
device name. The functions where this is problematic are:
* clk.c:__of_clk_get_from_provider()
* clkdev.c:clk_get_sys()

By the way in my new version I called the helpers:
* clk_{link,unlink}_hierarchy()
* clk_{link,unlink}_consumer()

I will send a new version with these helpers, but if you have anything
in mind to help me achieve the above request, I will welcome the idea.


Thanks,
Miquèl
Stephen Boyd Dec. 3, 2018, 7:20 p.m. UTC | #7
Quoting Miquel Raynal (2018-11-30 02:20:52)
> Hi Stephen,
> 
> Stephen Boyd <sboyd@kernel.org> wrote on Fri, 30 Nov 2018 01:26:20
> -0800:
> 
> > Quoting Miquel Raynal (2018-11-23 01:11:32)
> > > Would you agree with me adding dummy functions in the #else section
> > > like:
> > > 
> > > static inline void __clk_device_link(struct device *consumer, struct clk *clk)
> > > {
> > >        return;
> > > }
> > > 
> > > static inline void __clk_device_unlink(struct clk *clk)
> > > {
> > >        return;
> > > }
> > > 
> > > Do you want me to also declare these functions in the #if section
> > > (with the external keyword) to balance the above declarations?  
> > 
> > Why can't we do the linking in __clk_get() and __clk_put()?
> > 
> 
> Because we need the caller's 'struct device' to make the link and
> this is not available in __clk_get(). I tried to ad it as parameter but
> I don't think it is possible to retrieve a 'struct device' from the
> device name. The functions where this is problematic are:
> * clk.c:__of_clk_get_from_provider()
> * clkdev.c:clk_get_sys()
> 
> By the way in my new version I called the helpers:
> * clk_{link,unlink}_hierarchy()
> * clk_{link,unlink}_consumer()
> 
> I will send a new version with these helpers, but if you have anything
> in mind to help me achieve the above request, I will welcome the idea.
> 

We can do the linking in __clk_get() and __clk_put() if we poke into the
struct clk -> struct clk_core and bury the struct device into each
clk_core structure.
Miquel Raynal Dec. 3, 2018, 10:16 p.m. UTC | #8
Hi Stephen,

Stephen Boyd <sboyd@kernel.org> wrote on Mon, 03 Dec 2018 11:20:31
-0800:

> Quoting Miquel Raynal (2018-11-30 02:20:52)
> > Hi Stephen,
> > 
> > Stephen Boyd <sboyd@kernel.org> wrote on Fri, 30 Nov 2018 01:26:20
> > -0800:
> >   
> > > Quoting Miquel Raynal (2018-11-23 01:11:32)  
> > > > Would you agree with me adding dummy functions in the #else section
> > > > like:
> > > > 
> > > > static inline void __clk_device_link(struct device *consumer, struct clk *clk)
> > > > {
> > > >        return;
> > > > }
> > > > 
> > > > static inline void __clk_device_unlink(struct clk *clk)
> > > > {
> > > >        return;
> > > > }
> > > > 
> > > > Do you want me to also declare these functions in the #if section
> > > > (with the external keyword) to balance the above declarations?    
> > > 
> > > Why can't we do the linking in __clk_get() and __clk_put()?
> > >   
> > 
> > Because we need the caller's 'struct device' to make the link and
> > this is not available in __clk_get(). I tried to ad it as parameter but
> > I don't think it is possible to retrieve a 'struct device' from the
> > device name. The functions where this is problematic are:
> > * clk.c:__of_clk_get_from_provider()
> > * clkdev.c:clk_get_sys()
> > 
> > By the way in my new version I called the helpers:
> > * clk_{link,unlink}_hierarchy()
> > * clk_{link,unlink}_consumer()
> > 
> > I will send a new version with these helpers, but if you have anything
> > in mind to help me achieve the above request, I will welcome the idea.
> >   
> 
> We can do the linking in __clk_get() and __clk_put() if we poke into the
> struct clk -> struct clk_core and bury the struct device into each
> clk_core structure.
> 

I meant the consumer device's structure. Yes, from a struct clk, the
first change in patch 1/2 let's us do clk->core->dev to get the clock
device. But for linking I need both the clock device and the consumer
device; and the latter will be missing in __clk_get().


Thanks,
Miquèl
Stephen Boyd Dec. 3, 2018, 10:28 p.m. UTC | #9
Quoting Miquel Raynal (2018-12-03 14:16:55)
> Stephen Boyd <sboyd@kernel.org> wrote on Mon, 03 Dec 2018 11:20:31
> -0800:
> > Quoting Miquel Raynal (2018-11-30 02:20:52)
> > > Stephen Boyd <sboyd@kernel.org> wrote on Fri, 30 Nov 2018 01:26:20
> > > -0800:
> > > > Quoting Miquel Raynal (2018-11-23 01:11:32)  
> > > 
> > > Because we need the caller's 'struct device' to make the link and
> > > this is not available in __clk_get(). I tried to ad it as parameter but
> > > I don't think it is possible to retrieve a 'struct device' from the
> > > device name. The functions where this is problematic are:
> > > * clk.c:__of_clk_get_from_provider()
> > > * clkdev.c:clk_get_sys()
> > > 
> > > By the way in my new version I called the helpers:
> > > * clk_{link,unlink}_hierarchy()
> > > * clk_{link,unlink}_consumer()
> > > 
> > > I will send a new version with these helpers, but if you have anything
> > > in mind to help me achieve the above request, I will welcome the idea.
> > >   
> > 
> > We can do the linking in __clk_get() and __clk_put() if we poke into the
> > struct clk -> struct clk_core and bury the struct device into each
> > clk_core structure.
> > 
> 
> I meant the consumer device's structure. Yes, from a struct clk, the
> first change in patch 1/2 let's us do clk->core->dev to get the clock
> device. But for linking I need both the clock device and the consumer
> device; and the latter will be missing in __clk_get().
> 

Ah ok, sounds like this is how it has to be then.

Patch
diff mbox series

diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
index b799347c5fd6..33a0f2b0533a 100644
--- a/drivers/clk/clk.c
+++ b/drivers/clk/clk.c
@@ -90,6 +90,7 @@  struct clk {
 	unsigned long max_rate;
 	unsigned int exclusive_count;
 	struct hlist_node clks_node;
+	struct device_link *link;
 };
 
 /***           runtime pm          ***/
@@ -262,6 +263,25 @@  struct clk_hw *__clk_get_hw(struct clk *clk)
 }
 EXPORT_SYMBOL_GPL(__clk_get_hw);
 
+void __clk_device_link(struct device *consumer, struct clk *clk)
+{
+	if (!consumer || !clk || !clk->core)
+		return;
+
+	clk->link = device_link_add(consumer, clk->core->dev,
+				    DL_FLAG_STATELESS);
+}
+EXPORT_SYMBOL_GPL(__clk_device_link);
+
+void __clk_device_unlink(struct clk *clk)
+{
+	if (!clk || !clk->link)
+		return;
+
+	device_link_del(clk->link);
+}
+EXPORT_SYMBOL_GPL(__clk_device_unlink);
+
 unsigned int clk_hw_get_num_parents(const struct clk_hw *hw)
 {
 	return hw->core->num_parents;
diff --git a/drivers/clk/clkdev.c b/drivers/clk/clkdev.c
index 9ab3db8b3988..fccfd4c01457 100644
--- a/drivers/clk/clkdev.c
+++ b/drivers/clk/clkdev.c
@@ -194,20 +194,27 @@  EXPORT_SYMBOL(clk_get_sys);
 struct clk *clk_get(struct device *dev, const char *con_id)
 {
 	const char *dev_id = dev ? dev_name(dev) : NULL;
-	struct clk *clk;
+	struct clk *clk = NULL;
 
 	if (dev && dev->of_node) {
 		clk = __of_clk_get_by_name(dev->of_node, dev_id, con_id);
-		if (!IS_ERR(clk) || PTR_ERR(clk) == -EPROBE_DEFER)
+		if (PTR_ERR(clk) == -EPROBE_DEFER)
 			return clk;
 	}
 
-	return clk_get_sys(dev_id, con_id);
+	if (IS_ERR_OR_NULL(clk))
+		clk = clk_get_sys(dev_id, con_id);
+
+	if (!IS_ERR(clk))
+		__clk_device_link(dev, clk);
+
+	return clk;
 }
 EXPORT_SYMBOL(clk_get);
 
 void clk_put(struct clk *clk)
 {
+	__clk_device_unlink(clk);
 	__clk_put(clk);
 }
 EXPORT_SYMBOL(clk_put);
diff --git a/include/linux/clk-provider.h b/include/linux/clk-provider.h
index 60c51871b04b..c7ba8098f854 100644
--- a/include/linux/clk-provider.h
+++ b/include/linux/clk-provider.h
@@ -781,6 +781,8 @@  void devm_clk_hw_unregister(struct device *dev, struct clk_hw *hw);
 const char *__clk_get_name(const struct clk *clk);
 const char *clk_hw_get_name(const struct clk_hw *hw);
 struct clk_hw *__clk_get_hw(struct clk *clk);
+void __clk_device_link(struct device *consumer, struct clk *clk);
+void __clk_device_unlink(struct clk *clk);
 unsigned int clk_hw_get_num_parents(const struct clk_hw *hw);
 struct clk_hw *clk_hw_get_parent(const struct clk_hw *hw);
 struct clk_hw *clk_hw_get_parent_by_index(const struct clk_hw *hw,