cpufreq: interactive: allow arbitrary speed / delay mappings

Accept a string of delays and speeds at which to apply the delay before
raising each step above hispeed. For example, "80000 1300000:200000
1500000:40000" means that the delay at or above 1GHz, until 1.3GHz is 80 msecs,
the delay until 1.5GHz is 200 msecs and the delay at or above 1.5GHz is 40
msecs when hispeed_freq is 1GHz.

[toddpoynor@google.com: add documentation]
Change-Id: Ifeebede8b1acbdd0a53e5c6916bccbf764dc854f
Signed-off-by: Minsung Kim <ms925.kim@samsung.com>
diff --git a/Documentation/cpu-freq/governors.txt b/Documentation/cpu-freq/governors.txt
index 4d8ae34..ac8a37e 100644
--- a/Documentation/cpu-freq/governors.txt
+++ b/Documentation/cpu-freq/governors.txt
@@ -260,7 +260,17 @@
 
 above_hispeed_delay: When speed is at or above hispeed_freq, wait for
 this long before raising speed in response to continued high load.
-Default is 20000 uS.
+The format is a single delay value, optionally followed by pairs of
+CPU speeds and the delay to use at or above those speeds.  Colons can
+be used between the speeds and associated delays for readability.  For
+example:
+
+   80000 1300000:200000 1500000:40000
+
+uses delay 80000 uS until CPU speed 1.3 GHz, at which speed delay
+200000 uS is used until speed 1.5 GHz, at which speed (and above)
+delay 40000 uS is used.  If speeds are specified these must appear in
+ascending order.  Default is 20000 uS.
 
 timer_rate: Sample rate for reevaluating CPU load when the CPU is not
 idle.  A deferrable timer is used, such that the CPU will not be woken