PM_RAISE_POWER(9F) Kernel Functions for Drivers PM_RAISE_POWER(9F)


NAME


pm_raise_power, pm_lower_power - Raise or lower power of components

SYNOPSIS


#include <sys/ddi.h>
#include <sys/sunddi.h>

int pm_raise_power(dev_info_t *dip, int component, int level);


int pm_lower_power(dev_info_t *dip, int component, int level);


INTERFACE LEVEL


Solaris DDI specific (Solaris DDI)

PARAMETERS


pm_raise_power
dip
Pointer to the device's dev_info structure


component
The number of the component for which a power level change
is desired


level
The power level to which the indicated component will be
raised


pm_lower_power
dip
Pointer to the device's dev_info structure


component
Number of the component for which a power level change is
desired


level
Power level to which the indicated component will be lowered


DESCRIPTION


The pm_raise_power(9F) function requests the Power Management framework
to raise the power level of component of dip to at least level.


The state of the device should be examined before each physical access.
The pm_raise_power(9F) function should be called to set a component to
the required power level if the operation to be performed requires the
component to be at a power level higher than its current power level.


When pm_raise_power(9F) returns with success, the component is
guaranteed to be at least at the requested power level. All devices that
depend on this will be at their full power level. Since the actual device
power level may be higher than requested by the driver, the driver should
not make any assumption about the absolute power level on successful
return from pm_raise_power(9F).


The pm_raise_power(9F) function may cause re-entry of the driver
power(9E) to raise the power level. Deadlock may result if the driver
locks are held across the call to pm_raise_power(9F).


The pm_lower_power(9F) function requests the Power Management framework
to lower the power level of component of dip to at most level.


Normally, transitions to lower power levels are initiated by the Power
Management framework based on component idleness. However, when
detaching, the driver should also initiate reduced power levels by
setting the power level of all device components to their lowest levels.
The pm_lower_power(9F) function is intended for this use only, and will
return DDI_FAILURE if the driver is not detaching at the time of the
call.


If automatic Power Management is disabled (see dtpower(1M) and
power.conf(4)), pm_lower_power(9F) returns DDI_SUCCESS without changing
the power level of the component. Otherwise, when pm_lower_power(9F)
returns with success, the component is guaranteed to be at most at the
requested power level. Since the actual device power level may be lower
than requested by the driver, the driver should not make any assumption
about the absolute power level on successful return from
pm_lower_power(9F).


The pm_lower_power(9F) function may cause re-entry of the driver
power(9E) to lower the power level. Deadlock may result if the driver
locks are held across the call to pm_lower_power(9F).

Note -

If these functions are called as a result of entry into the driver's
attach(9E), detach(9E) or power(9E) entry point, these functions must
be called from the same thread which entered attach(9E), detach(9E) or
power(9E).

RETURN VALUES


The pm_raise_power(9F) function returns:

DDI_SUCCESS
Component is now at the requested power level or higher.


DDI_FAILURE
Component or level is out of range, or the framework was
unable to raise the power level of the component to the
requested level.


The pm_lower_power(9F) function returns:

DDI_SUCCESS
Component is now at the requested power level or lower,
or automatic Power Management is disabled.


DDI_FAILURE
Component or level is out of range, or the framework was
unable to lower the power level of the component to the
requested level, or the device is not detaching.


EXAMPLES


A hypothetical disk driver might include this code to handle
pm_raise_power(9F):

static int
xxdisk_strategy(struct buf *bp)
{

...

/*
* At this point we have determined that we need to raise the
* power level of the device. Since we have to drop the
* mutex, we need to take care of case where framework is
* lowering power at the same time we are raising power.
* We resolve this by marking the device busy and failing
* lower power in power() entry point when device is busy.
*/

ASSERT(mutex_owned(xsp->lock));
if (xsp->pm_busycnt < 1) {
/*
* Component is not already marked busy
*/
if (pm_busy_component(xsp->dip,
XXDISK_COMPONENT) != DDI_SUCCESS) {
bioerror(bp,EIO);
biodone(bp);
return (0);
}
xsp->pm_busycnt++;
}
mutex_exit(xsp->lock);
if (pm_raise_power(xsp->dip,
XXDISK_COMPONENT, XXPOWER_SPUN_UP) != DDI_SUCCESS) {
bioerror(bp,EIO);
biodone(bp);
return (0);
}
mutex_enter(xsp->lock);

....

}


xxdisk_power(dev_info *dip, int comp, int level)
{

...

/*
* We fail the power() entry point if the device is busy and
* request is to lower the power level.

*/

ASSERT(mutex_owned( xsp->lock));
if (xsp->pm_busycnt >= 1) {
if (level < xsp->cur_level) {
mutex_exit( xsp->lock);
return (DDI_FAILURE);
}
}

...

}


CONTEXT


These functions can be called from user or kernel context.

ATTRIBUTES


See attributes(5) for a description of the following attribute:


+--------------------+-----------------+
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
+--------------------+-----------------+
|Interface stability | Committed |
+--------------------+-----------------+

SEE ALSO


power.conf(4), pm(7D), attach(9E), detach(9E), power(9E),
pm_busy_component(9F), pm_idle_component(9F), pm(9P), pm-components(9P)


Writing Device Drivers


March 22, 2005 PM_RAISE_POWER(9F)