[PATCH/RFC 0/2] initial runtime PM layer for OMAP

[PATCH/RFC 0/2] initial runtime PM layer for OMAP

[Kevin Hilman]

Here's a first pass implementaton at the runtime PM layer for OMAP.
As you can see, it's a pretty thin layer and the omap_device layer
does all the heavy lifting.

Following shortly to this series will be a conversion of the MMC
driver as an example of how to use the runtime PM API.

Kevin Hilman (2):
  OMAP: omap_device: add omap_device_has_lost_context()
  OMAP: PM: initial runtime PM support

 arch/arm/mach-omap2/Makefile                  |    6 ++
 arch/arm/mach-omap2/pm_runtime.c              |  119 +++++++++++++++++++++++++
 arch/arm/plat-omap/include/plat/omap_device.h |    3 +
 arch/arm/plat-omap/omap_device.c              |   35 +++++++
 4 files changed, 163 insertions(+), 0 deletions(-)
 create mode 100644 arch/arm/mach-omap2/pm_runtime.c

[PATCH/RFC 1/2] OMAP: omap_device: add omap_device_has_lost_context()

[Kevin Hilman]

Add new function omap_device_has_lost_context() as a simple check
to be used after omap_device_enable() to determine if device has
lost context (and thus needs context restore.)

Motivation: Currently, each driver needs to read the context-loss
count before suspend, and again upon resume to determine if
device context needs to be restored.  Rather than duplicating
this process across all drivers, move it into omap_device.  After
omap_device_enable(), omap_device_has_lost_context() can be called
to determine if context was lost.

This API is not intended for direct use by drivers.  Rather, the
OMAP runtime PM core will use this to determine whether or not
to call the drivers runtime_resume hook which can then be used to
restore context.

The goal is to only call drivers "restore" hook when necessary.

Signed-off-by: Kevin Hilman <khilman@deeprootsystems.com>
---
 arch/arm/plat-omap/include/plat/omap_device.h |    3 ++
 arch/arm/plat-omap/omap_device.c              |   35 +++++++++++++++++++++++++
 2 files changed, 38 insertions(+), 0 deletions(-)

diff --git a/arch/arm/plat-omap/include/plat/omap_device.h b/arch/arm/plat-omap/include/plat/omap_device.h
index 76d4917..ff98eb4 100644
--- a/arch/arm/plat-omap/include/plat/omap_device.h
+++ b/arch/arm/plat-omap/include/plat/omap_device.h
@@ -71,6 +71,8 @@ struct omap_device {
 	s8				pm_lat_level;
 	u8				hwmods_cnt;
 	u8				_state;
+	u32                             activate_loss_cnt;
+	u32                             deactivate_loss_cnt;
 };
 
 /* Device driver interface (call via platform_data fn ptrs) */
@@ -78,6 +80,7 @@ struct omap_device {
 int omap_device_enable(struct platform_device *pdev);
 int omap_device_idle(struct platform_device *pdev);
 int omap_device_shutdown(struct platform_device *pdev);
+bool omap_device_has_lost_context(struct platform_device *pdev);
 
 /* Core code interface */
 
diff --git a/arch/arm/plat-omap/omap_device.c b/arch/arm/plat-omap/omap_device.c
index d8c75c8..aaa009d 100644
--- a/arch/arm/plat-omap/omap_device.c
+++ b/arch/arm/plat-omap/omap_device.c
@@ -84,6 +84,7 @@
 
 #include <plat/omap_device.h>
 #include <plat/omap_hwmod.h>
+#include <plat/powerdomain.h>
 
 /* These parameters are passed to _omap_device_{de,}activate() */
 #define USE_WAKEUP_LAT			0
@@ -119,6 +120,7 @@
 static int _omap_device_activate(struct omap_device *od, u8 ignore_lat)
 {
 	struct timespec a, b, c;
+	struct powerdomain *pwrdm;
 
 	pr_debug("omap_device: %s: activating\n", od->pdev.name);
 
@@ -168,6 +170,10 @@ static int _omap_device_activate(struct omap_device *od, u8 ignore_lat)
 		od->dev_wakeup_lat -= odpl->activate_lat;
 	}
 
+	pwrdm = omap_device_get_pwrdm(od);
+	if (pwrdm)
+		od->activate_loss_cnt = pwrdm->state_counter[PWRDM_POWER_OFF];
+
 	return 0;
 }
 
@@ -188,6 +194,7 @@ static int _omap_device_activate(struct omap_device *od, u8 ignore_lat)
 static int _omap_device_deactivate(struct omap_device *od, u8 ignore_lat)
 {
 	struct timespec a, b, c;
+	struct powerdomain *pwrdm;
 
 	pr_debug("omap_device: %s: deactivating\n", od->pdev.name);
 
@@ -239,6 +246,10 @@ static int _omap_device_deactivate(struct omap_device *od, u8 ignore_lat)
 		od->pm_lat_level++;
 	}
 
+	pwrdm = omap_device_get_pwrdm(od);
+	if (pwrdm)
+		od->deactivate_loss_cnt = pwrdm->state_counter[PWRDM_POWER_OFF];
+
 	return 0;
 }
 
@@ -560,6 +571,30 @@ int omap_device_shutdown(struct platform_device *pdev)
 }
 
 /**
+ * omap_device_has_lost_context() - check if omap_device has lost context
+ * @od: struct omap_device *
+ *
+ * When an omap_device has been deactivated via omap_device_idle() or
+ * omap_device_shutdown() and then (re)activated using omap_device_enable()
+ * This function should be used to determine if the omap_device has
+ * lost context (due to an off-mode transistion)
+ */
+bool omap_device_has_lost_context(struct platform_device *pdev)
+{
+	struct omap_device *od;
+
+	od = _find_by_pdev(pdev);
+
+	if (od->_state != OMAP_DEVICE_STATE_ENABLED) {
+		WARN(1, "omap_device: %s.%d: has_lost_context() called "
+		     "from invalid state\n", od->pdev.name, od->pdev.id);
+		return -EINVAL;
+	}
+
+	return (od->activate_loss_cnt != od->deactivate_loss_cnt);
+}
+
+/**
  * omap_device_align_pm_lat - activate/deactivate device to match wakeup lat lim
  * @od: struct omap_device *
  *
-- 
1.6.6

Re: [PATCH/RFC 1/2] OMAP: omap_device: add omap_device_has_lost_context()

[Paul Walmsley]

Hi Kevin,

a few questions:

On Wed, 3 Feb 2010, Kevin Hilman wrote:

> Add new function omap_device_has_lost_context() as a simple check
> to be used after omap_device_enable() to determine if device has
> lost context (and thus needs context restore.)
> 
> Motivation: Currently, each driver needs to read the context-loss
> count before suspend, and again upon resume to determine if
> device context needs to be restored.  Rather than duplicating
> this process across all drivers, move it into omap_device.  After
> omap_device_enable(), omap_device_has_lost_context() can be called
> to determine if context was lost.
> 
> This API is not intended for direct use by drivers.  Rather, the
> OMAP runtime PM core will use this to determine whether or not
> to call the drivers runtime_resume hook which can then be used to
> restore context.
> 
> The goal is to only call drivers "restore" hook when necessary.
> 
> Signed-off-by: Kevin Hilman <khilman@deeprootsystems.com>
> ---
>  arch/arm/plat-omap/include/plat/omap_device.h |    3 ++
>  arch/arm/plat-omap/omap_device.c              |   35 +++++++++++++++++++++++++
>  2 files changed, 38 insertions(+), 0 deletions(-)
> 
> diff --git a/arch/arm/plat-omap/include/plat/omap_device.h b/arch/arm/plat-omap/include/plat/omap_device.h
> index 76d4917..ff98eb4 100644
> --- a/arch/arm/plat-omap/include/plat/omap_device.h
> +++ b/arch/arm/plat-omap/include/plat/omap_device.h
> @@ -71,6 +71,8 @@ struct omap_device {
>  	s8				pm_lat_level;
>  	u8				hwmods_cnt;
>  	u8				_state;
> +	u32                             activate_loss_cnt;
> +	u32                             deactivate_loss_cnt;

Would it be sufficient to just note the context loss count on a disable 
and then compare it against the powerdomain's loss count during activate, 
and if different, set a flag in _state ?  That way only one loss count 
variable would be needed.

>  };
>  
>  /* Device driver interface (call via platform_data fn ptrs) */
> @@ -78,6 +80,7 @@ struct omap_device {
>  int omap_device_enable(struct platform_device *pdev);
>  int omap_device_idle(struct platform_device *pdev);
>  int omap_device_shutdown(struct platform_device *pdev);
> +bool omap_device_has_lost_context(struct platform_device *pdev);
>  
>  /* Core code interface */
>  
> diff --git a/arch/arm/plat-omap/omap_device.c b/arch/arm/plat-omap/omap_device.c
> index d8c75c8..aaa009d 100644
> --- a/arch/arm/plat-omap/omap_device.c
> +++ b/arch/arm/plat-omap/omap_device.c
> @@ -84,6 +84,7 @@
>  
>  #include <plat/omap_device.h>
>  #include <plat/omap_hwmod.h>
> +#include <plat/powerdomain.h>
>  
>  /* These parameters are passed to _omap_device_{de,}activate() */
>  #define USE_WAKEUP_LAT			0
> @@ -119,6 +120,7 @@
>  static int _omap_device_activate(struct omap_device *od, u8 ignore_lat)
>  {
>  	struct timespec a, b, c;
> +	struct powerdomain *pwrdm;
>  
>  	pr_debug("omap_device: %s: activating\n", od->pdev.name);
>  
> @@ -168,6 +170,10 @@ static int _omap_device_activate(struct omap_device *od, u8 ignore_lat)
>  		od->dev_wakeup_lat -= odpl->activate_lat;
>  	}
>  
> +	pwrdm = omap_device_get_pwrdm(od);
> +	if (pwrdm)
> +		od->activate_loss_cnt = pwrdm->state_counter[PWRDM_POWER_OFF];

This probably will also depend on the powerdomain's logic_retst, 
mem_retst, mem_onst bits, since context can be lost even when the 
powerdomain is in RET or ON state.


> +
>  	return 0;
>  }
>  
> @@ -188,6 +194,7 @@ static int _omap_device_activate(struct omap_device *od, u8 ignore_lat)
>  static int _omap_device_deactivate(struct omap_device *od, u8 ignore_lat)
>  {
>  	struct timespec a, b, c;
> +	struct powerdomain *pwrdm;
>  
>  	pr_debug("omap_device: %s: deactivating\n", od->pdev.name);
>  
> @@ -239,6 +246,10 @@ static int _omap_device_deactivate(struct omap_device *od, u8 ignore_lat)
>  		od->pm_lat_level++;
>  	}
>  
> +	pwrdm = omap_device_get_pwrdm(od);
> +	if (pwrdm)
> +		od->deactivate_loss_cnt = pwrdm->state_counter[PWRDM_POWER_OFF];

Same comment as above.

> +
>  	return 0;
>  }
>  
> @@ -560,6 +571,30 @@ int omap_device_shutdown(struct platform_device *pdev)
>  }
>  
>  /**
> + * omap_device_has_lost_context() - check if omap_device has lost context
> + * @od: struct omap_device *
> + *
> + * When an omap_device has been deactivated via omap_device_idle() or
> + * omap_device_shutdown() and then (re)activated using omap_device_enable()
> + * This function should be used to determine if the omap_device has
> + * lost context (due to an off-mode transistion)
> + */
> +bool omap_device_has_lost_context(struct platform_device *pdev)
> +{
> +	struct omap_device *od;
> +
> +	od = _find_by_pdev(pdev);
> +
> +	if (od->_state != OMAP_DEVICE_STATE_ENABLED) {
> +		WARN(1, "omap_device: %s.%d: has_lost_context() called "
> +		     "from invalid state\n", od->pdev.name, od->pdev.id);
> +		return -EINVAL;
> +	}
> +
> +	return (od->activate_loss_cnt != od->deactivate_loss_cnt);
> +}
> +
> +/**
>   * omap_device_align_pm_lat - activate/deactivate device to match wakeup lat lim
>   * @od: struct omap_device *
>   *
> -- 
> 1.6.6
> 
> --
> To unsubscribe from this list: send the line "unsubscribe linux-omap" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html
> 


- Paul

Re: [PATCH/RFC 1/2] OMAP: omap_device: add omap_device_has_lost_context()

[Kevin Hilman]

Paul Walmsley <paul@pwsan.com> writes:

> Hi Kevin,
>
> a few questions:
>
> On Wed, 3 Feb 2010, Kevin Hilman wrote:
>
>> Add new function omap_device_has_lost_context() as a simple check
>> to be used after omap_device_enable() to determine if device has
>> lost context (and thus needs context restore.)
>> 
>> Motivation: Currently, each driver needs to read the context-loss
>> count before suspend, and again upon resume to determine if
>> device context needs to be restored.  Rather than duplicating
>> this process across all drivers, move it into omap_device.  After
>> omap_device_enable(), omap_device_has_lost_context() can be called
>> to determine if context was lost.
>> 
>> This API is not intended for direct use by drivers.  Rather, the
>> OMAP runtime PM core will use this to determine whether or not
>> to call the drivers runtime_resume hook which can then be used to
>> restore context.
>> 
>> The goal is to only call drivers "restore" hook when necessary.
>> 
>> Signed-off-by: Kevin Hilman <khilman@deeprootsystems.com>
>> ---
>>  arch/arm/plat-omap/include/plat/omap_device.h |    3 ++
>>  arch/arm/plat-omap/omap_device.c              |   35 +++++++++++++++++++++++++
>>  2 files changed, 38 insertions(+), 0 deletions(-)
>> 
>> diff --git a/arch/arm/plat-omap/include/plat/omap_device.h b/arch/arm/plat-omap/include/plat/omap_device.h
>> index 76d4917..ff98eb4 100644
>> --- a/arch/arm/plat-omap/include/plat/omap_device.h
>> +++ b/arch/arm/plat-omap/include/plat/omap_device.h
>> @@ -71,6 +71,8 @@ struct omap_device {
>>  	s8				pm_lat_level;
>>  	u8				hwmods_cnt;
>>  	u8				_state;
>> +	u32                             activate_loss_cnt;
>> +	u32                             deactivate_loss_cnt;
>
> Would it be sufficient to just note the context loss count on a disable 
> and then compare it against the powerdomain's loss count during activate, 
> and if different, set a flag in _state ?  That way only one loss count 
> variable would be needed.

That's possible, but when should that flag be cleared?  when
has_lost_context() is called?  Maybe before _deactivate() actually
does the deactivate?  Thoughts?

>>  };
>>  
>>  /* Device driver interface (call via platform_data fn ptrs) */
>> @@ -78,6 +80,7 @@ struct omap_device {
>>  int omap_device_enable(struct platform_device *pdev);
>>  int omap_device_idle(struct platform_device *pdev);
>>  int omap_device_shutdown(struct platform_device *pdev);
>> +bool omap_device_has_lost_context(struct platform_device *pdev);
>>  
>>  /* Core code interface */
>>  
>> diff --git a/arch/arm/plat-omap/omap_device.c b/arch/arm/plat-omap/omap_device.c
>> index d8c75c8..aaa009d 100644
>> --- a/arch/arm/plat-omap/omap_device.c
>> +++ b/arch/arm/plat-omap/omap_device.c
>> @@ -84,6 +84,7 @@
>>  
>>  #include <plat/omap_device.h>
>>  #include <plat/omap_hwmod.h>
>> +#include <plat/powerdomain.h>
>>  
>>  /* These parameters are passed to _omap_device_{de,}activate() */
>>  #define USE_WAKEUP_LAT			0
>> @@ -119,6 +120,7 @@
>>  static int _omap_device_activate(struct omap_device *od, u8 ignore_lat)
>>  {
>>  	struct timespec a, b, c;
>> +	struct powerdomain *pwrdm;
>>  
>>  	pr_debug("omap_device: %s: activating\n", od->pdev.name);
>>  
>> @@ -168,6 +170,10 @@ static int _omap_device_activate(struct omap_device *od, u8 ignore_lat)
>>  		od->dev_wakeup_lat -= odpl->activate_lat;
>>  	}
>>  
>> +	pwrdm = omap_device_get_pwrdm(od);
>> +	if (pwrdm)
>> +		od->activate_loss_cnt = pwrdm->state_counter[PWRDM_POWER_OFF];
>
> This probably will also depend on the powerdomain's logic_retst, 
> mem_retst, mem_onst bits, since context can be lost even when the 
> powerdomain is in RET or ON state.

Agreed.  

Seems like this type of thing belongs in the powerdomain layer, don't
you think?  Maybe, along with the OSWR patches, we can add some more
checking/accounting for whether a domain has gone off (or needs
restore.)

Kevin

>
>> +
>>  	return 0;
>>  }
>>  
>> @@ -188,6 +194,7 @@ static int _omap_device_activate(struct omap_device *od, u8 ignore_lat)
>>  static int _omap_device_deactivate(struct omap_device *od, u8 ignore_lat)
>>  {
>>  	struct timespec a, b, c;
>> +	struct powerdomain *pwrdm;
>>  
>>  	pr_debug("omap_device: %s: deactivating\n", od->pdev.name);
>>  
>> @@ -239,6 +246,10 @@ static int _omap_device_deactivate(struct omap_device *od, u8 ignore_lat)
>>  		od->pm_lat_level++;
>>  	}
>>  
>> +	pwrdm = omap_device_get_pwrdm(od);
>> +	if (pwrdm)
>> +		od->deactivate_loss_cnt = pwrdm->state_counter[PWRDM_POWER_OFF];
>
> Same comment as above.
>
>> +
>>  	return 0;
>>  }
>>  
>> @@ -560,6 +571,30 @@ int omap_device_shutdown(struct platform_device *pdev)
>>  }
>>  
>>  /**
>> + * omap_device_has_lost_context() - check if omap_device has lost context
>> + * @od: struct omap_device *
>> + *
>> + * When an omap_device has been deactivated via omap_device_idle() or
>> + * omap_device_shutdown() and then (re)activated using omap_device_enable()
>> + * This function should be used to determine if the omap_device has
>> + * lost context (due to an off-mode transistion)
>> + */
>> +bool omap_device_has_lost_context(struct platform_device *pdev)
>> +{
>> +	struct omap_device *od;
>> +
>> +	od = _find_by_pdev(pdev);
>> +
>> +	if (od->_state != OMAP_DEVICE_STATE_ENABLED) {
>> +		WARN(1, "omap_device: %s.%d: has_lost_context() called "
>> +		     "from invalid state\n", od->pdev.name, od->pdev.id);
>> +		return -EINVAL;
>> +	}
>> +
>> +	return (od->activate_loss_cnt != od->deactivate_loss_cnt);
>> +}
>> +
>> +/**
>>   * omap_device_align_pm_lat - activate/deactivate device to match wakeup lat lim
>>   * @od: struct omap_device *
>>   *
>> -- 
>> 1.6.6
>> 
>> --
>> To unsubscribe from this list: send the line "unsubscribe linux-omap" in
>> the body of a message to majordomo@vger.kernel.org
>> More majordomo info at  http://vger.kernel.org/majordomo-info.html
>> 
>
>
> - Paul

[PATCH/RFC 2/2] OMAP: PM: initial runtime PM support

[Kevin Hilman]

Implement the new runtime PM framework as a thin layer on top of the
omap_device API.  Since we don't have an OMAP-specific bus, override
the runtime PM hooks for the platform_bus for the OMAP specific
implementation.

While the runtime PM API has three main states (idle, suspend, resume)
This version treats idle and suspend the same way by implementing both
on top of omap_device_disable().

Device driver ->runtime_suspend() hooks are called just before the
device is disabled (via omap_device_idle()), and device driver
->runtime_resume() hooks are called just after device has been
enabled, but ONLY IF device has lost context due to an off-mode
transition.

To convert other device drivers, simply change clk_disable() calls to
pm_runtime_put_sync() and clk_enable() calls to pm_runtime_get_sync().

NOTE: the bus notifier stuff is currently there for debug purposes.
      In the future, we may want to use the notifiers to do some
      automatic enable/disabling of devices.

Signed-off-by: Kevin Hilman <khilman@deeprootsystems.com>
---
 arch/arm/mach-omap2/Makefile     |    6 ++
 arch/arm/mach-omap2/pm_runtime.c |  119 ++++++++++++++++++++++++++++++++++++++
 2 files changed, 125 insertions(+), 0 deletions(-)
 create mode 100644 arch/arm/mach-omap2/pm_runtime.c

diff --git a/arch/arm/mach-omap2/Makefile b/arch/arm/mach-omap2/Makefile
index dba44a1..16ba8fc 100644
--- a/arch/arm/mach-omap2/Makefile
+++ b/arch/arm/mach-omap2/Makefile
@@ -55,6 +55,12 @@ obj-$(CONFIG_PM_DEBUG)			+= pm-debug.o
 AFLAGS_sleep24xx.o			:=-Wa,-march=armv6
 AFLAGS_sleep34xx.o			:=-Wa,-march=armv7-a
 
+# Runtime PM support
+obj-$(CONFIG_PM_RUNTIME)		+= pm_runtime.o
+ifeq ($(CONFIG_PM_VERBOSE),y)
+CFLAGS_pm_runtime.o                     += -DDEBUG
+endif
+
 endif
 
 # PRCM
diff --git a/arch/arm/mach-omap2/pm_runtime.c b/arch/arm/mach-omap2/pm_runtime.c
new file mode 100644
index 0000000..4bd1b9a
--- /dev/null
+++ b/arch/arm/mach-omap2/pm_runtime.c
@@ -0,0 +1,119 @@
+/*
+ * Runtime PM support code for OMAP
+ *
+ * Author: Kevin Hilman, Deep Root Systems, LLC
+ *
+ * Copyright (C) 2010 Texas Instruments, Inc.
+ *
+ * This file is licensed under the terms of the GNU General Public
+ * License version 2. This program is licensed "as is" without any
+ * warranty of any kind, whether express or implied.
+ */
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/io.h>
+#include <linux/pm_runtime.h>
+#include <linux/platform_device.h>
+#include <linux/mutex.h>
+
+#include <plat/omap_device.h>
+#include <plat/omap-pm.h>
+
+int platform_pm_runtime_suspend(struct device *dev)
+{
+	struct platform_device *pdev = to_platform_device(dev);
+	struct omap_device *odev = to_omap_device(pdev);
+	int ret = 0;
+
+	if (WARN_ON(!omap_device_is_valid(odev)))
+		return -ENODEV;
+
+	dev_dbg(dev, "%s\n", __func__);
+
+	if (dev->driver->pm && dev->driver->pm->runtime_suspend)
+		ret = dev->driver->pm->runtime_suspend(dev);
+	if (!ret)
+		omap_device_idle(pdev);
+
+	return ret;
+};
+
+int platform_pm_runtime_resume(struct device *dev)
+{
+	struct platform_device *pdev = to_platform_device(dev);
+	struct omap_device *odev = to_omap_device(pdev);
+	int ret = 0;
+
+	if (WARN_ON(!omap_device_is_valid(odev)))
+		return -ENODEV;
+
+	dev_dbg(dev, "%s\n", __func__);
+
+	omap_device_enable(pdev);
+
+	/*
+	 * TODO: only call drivers runtime_resume hook if
+	 *       device has lost context.
+	 */
+	if (dev->driver->pm && dev->driver->pm->runtime_resume)
+		if (omap_device_has_lost_context(pdev))
+			ret = dev->driver->pm->runtime_resume(dev);
+
+	return ret;
+};
+
+int platform_pm_runtime_idle(struct device *dev)
+{
+	struct platform_device *pdev = to_platform_device(dev);
+	struct omap_device *odev = to_omap_device(pdev);
+	int ret;
+
+	if (WARN_ON(!omap_device_is_valid(odev)))
+		return -ENODEV;
+
+	ret = pm_runtime_suspend(dev);
+	dev_dbg(dev, "%s [%d] \n", __func__, ret);
+
+	return 0;
+};
+
+static int platform_bus_notify(struct notifier_block *nb,
+			       unsigned long action, void *data)
+{
+	struct device *dev = data;
+	struct platform_device *pdev = to_platform_device(dev);
+	struct omap_device *odev = to_omap_device(pdev);
+
+	if (!omap_device_is_valid(odev))
+		return -ENODEV;
+
+	switch (action) {
+	case BUS_NOTIFY_ADD_DEVICE:
+		dev_dbg(dev, "BUS_NOTIFY_ADD_DEVICE");
+		break;
+	case BUS_NOTIFY_BOUND_DRIVER:
+		dev_dbg(dev, "BUS_NOTIFY_BOUND_DRIVER");
+		break;
+	case BUS_NOTIFY_UNBOUND_DRIVER:
+		dev_dbg(dev, "BUS_NOTIFY_UNBOUND_DRIVER");
+		break;
+	case BUS_NOTIFY_DEL_DEVICE:
+		dev_dbg(dev, "BUS_NOTIFY_DEL_DEVICE");
+		break;
+	default:
+		dev_dbg(dev, "Unknown");
+	}
+
+	return 0;
+}
+
+static struct notifier_block platform_bus_notifier = {
+	.notifier_call = platform_bus_notify
+};
+
+static int __init omap_pm_runtime_init(void)
+{
+	bus_register_notifier(&platform_bus_type, &platform_bus_notifier);
+	return 0;
+}
+core_initcall(omap_pm_runtime_init);
-- 
1.6.6