EDP: update documentation

Adding documentation about debugfs features and tegra specific
implementation.

Change-Id: I087391b522ee89cfe7a75ad44c4ea005c139c1b2
Signed-off-by: Sivaram Nair <sivaramn@nvidia.com>
(cherry picked from commit c6844e9af030d13b1a664c1d1a5f1b74c4659234)
Reviewed-on: http://git-master/r/204589
Reviewed-by: Automatic_Commit_Validation_User
Reviewed-by: Juha Tukkinen <jtukkinen@nvidia.com>
Reviewed-by: Diwakar Tundlam <dtundlam@nvidia.com>

2 files changed, 44 insertions, 0 deletions

diff --git a/Documentation/edp/debugfs b/Documentation/edp/debugfs
new file mode 100644
index 000000000000..654eb259c512
--- /dev/null
+++ b/Documentation/edp/debugfs
@@ -0,0 +1,36 @@
+
+EDP DEBUGFS
+
+1. Introduction
+
+EDP debugfs root is at /sys/kernel/debug/edp. Manager and client objects
+appear as subfolders under the root, forming a tree structure similar to
+the EDP sysfs entries.
+
+Following sections describe the debufs attributes. Unless stated
+otherwise, all attributes have RW permissions.
+
+2. EDP manager
+
+	[1] cap: Peak current capacity - reading will return the present
+	    value and writting will set a new cap. Note that the cap can
+	    not be set lower than the sum of E0 currents of all clients.
+	    Lowering the cap might result in throttling of clients.
+
+	[2] status (read-only): Gives a snap shot of the manager and its
+	    budget distribution.
+
+3. EDP clients
+
+Following is the list of common client attributes. The client driver may
+add additional device specfic attributes under the same folder.
+
+	[1] current: Force a certain client's E-state. Write the state
+	    index to force the state. Read will return the state value.
+	    The request is processed only if it can be handled fully
+	    (that is, the client will not be assigned a lesser E-state).
+	    If the state can not be changed due to insufficient budget,
+	    the operation fails.  Note that this request may be
+	    overriden by other requests. To prevent this from happening,
+	    choose the debug policy governor (see the EDP governor
+	    documentation).
diff --git a/Documentation/edp/governors b/Documentation/edp/governors
index 5dc7b7107d35..30e12b200a00 100644
--- a/Documentation/edp/governors
+++ b/Documentation/edp/governors
@@ -74,3 +74,11 @@ client is throttled first.
 8. Round Robin (RR)
 
 In this policy, clients are throttled in a round-robin fashion.
+
+9. Debug
+
+When the debug policy governor is selected, the framework stops
+processing requests from clients. Further changes to the client E-states
+can only be made manually via debugfs (see the EDP debugfs
+documentation). This allows one to do manual budget allocations and
+prevent clients from overriding them.