dvfs_client

Client for interacting with a Dynamic Voltage Frequency Scaling driver

Syntax:

dvfs_client

Runs on:

QNX Neutrino

Targets:

ARMv7

Options:

None.

Description:

The dvfs_client utility provides a way for you to interact with a dvfsmgr-* driver.

Run this utility with no options. It will register itself under /dev/dvfs_client_#, where # is the instance number of the client. You can have a maximum of nine concurrent DVFS clients.

Use echo and cat to send commands to the DVFS driver. For example, to read the driver's status:

# cat /dev/dvfs_client_1

You can set DVFS driver's mode like this:

echo option > /dev/dvfs_client_#

Note: You can do this only if the driver is in automatic mode.

The option is one of:

MM: set to manual mode.
MS: set to semi-automatic mode.
MA: set to automatic mode.

Change the power level like this:

echo level > /dev/dvfs_client_#

Note: This can be done only by the client that sets the DVFS driver's mode to manual or semi-automatic.

The level is one of:

PU: increase the power level.
PD: decrease the power level.
PX: set the power level to the maximum.
PM: set the power level to the minimum.

To set minimum level of performance:

echo Slevel > /dev/dvfs_client_#

To unset a previously set minimum level:

echo U > /dev/dvfs_client_#

Note: You can set or unset the minimum level only if the DVFS driver is in automatic mode.

The DVFS driver responds to the device control (devctl()) messages listed below. Some commands may be valid only for a certain driver mode, as indicated.

DVFS_DEVCTL_SET_MIN: Set the minimum level of power (automatic mode).
DVFS_DEVCTL_UNSET_MIN: Unset the minimum power level (automatic mode).
DVFS_DEVCTL_SET_MODE: Set the driver mode.
DVFS_DEVCTL_SET_PWR_LVL: Set the driver's power level (manual or semi-automatic).
DVFS_DEVCTL_GETSTATUS: Get the driver's status.
DVFS_DEVCTL_RUN_MAX: Run at the maximum power level (manual or semi-automatic).
DVFS_DEVCTL_RUN_MIN: Run at the minimum power level (manual or semi-automatic).

For more information, see the Writing a DVFS Driver technote.