PM / devfreq: Add new up_threshold and down_differential sysfs attrs

The up_threshold and down_differential variables were used to determine
the next frequency on simple_ondemand governor. It was possible to tune
two values by devfreq device driver. But on user-space, could not change
the them at the runtime for the tunning.

In order to support the tuning the up_threshold and down_differential
on user-space, add new following new sysfs attributes:
  : /sys/class/devfreq/[devfreq dev name]/up_threshold (range: [0, 100])
  : /sys/class/devfreq/[devfreq dev name]/down_differential (range: [0,100])

[Definition for governor attribute]
- DEVFREQ_GOV_ATTR_UP_THRESHOLD
  : /sys/class/devfreq/[devfreq dev name]/up_threshold
- DEVFREQ_GOV_ATTR_DOWN_DIFF
  : /sys/class/devfreq/[devfreq dev name]/down_differential

These attributes are used for only simple_ondemand governor until now
as following:
------------------------------------------------------------------------------
                      | simple    | perfor | power | user | passive | tegra30
		      | ondemand  | mance  | save  | space|         |
------------------------------------------------------------------------------
(skip of other attrs) |
up_threshold          | O         | X      | X     | X    | X       | X
down_differential     | O         | X      | X     | X    | X       | X
------------------------------------------------------------------------------

Signed-off-by: Chanwoo Choi <cw00.choi@samsung.com>
11 files changed