Documentation: PM: QoS: Update to reflect previous code changes

Update the PM QoS documentation to reflect the previous code changes
regarding the removal of PM QoS classes and the CPU latency QoS API
rework.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Reviewed-by: Ulf Hansson <ulf.hansson@linaro.org>
Reviewed-by: Amit Kucheria <amit.kucheria@linaro.org>
Tested-by: Amit Kucheria <amit.kucheria@linaro.org>

1 files changed, 39 insertions, 47 deletions

diff --git a/Documentation/power/pm_qos_interface.rst b/Documentation/power/pm_qos_interface.rst
index 0d62d506caf0..064f668fbdab 100644
--- a/Documentation/power/pm_qos_interface.rst
+++ b/Documentation/power/pm_qos_interface.rst
@@ -7,86 +7,78 @@ performance expectations by drivers, subsystems and user space applications on
 one of the parameters.
 
 Two different PM QoS frameworks are available:
-1. PM QoS classes for cpu_dma_latency
+1. CPU latency QoS.
 2. The per-device PM QoS framework provides the API to manage the
    per-device latency constraints and PM QoS flags.
 
-Each parameters have defined units:
-
- * latency: usec
- * timeout: usec
- * throughput: kbs (kilo bit / sec)
- * memory bandwidth: mbs (mega bit / sec)
+The latency unit used in the PM QoS framework is the microsecond (usec).
 
 
 1. PM QoS framework
 ===================
 
-The infrastructure exposes multiple misc device nodes one per implemented
-parameter.  The set of parameters implement is defined by pm_qos_power_init()
-and pm_qos_params.h.  This is done because having the available parameters
-being runtime configurable or changeable from a driver was seen as too easy to
-abuse.
-
-For each parameter a list of performance requests is maintained along with
-an aggregated target value.  The aggregated target value is updated with
-changes to the request list or elements of the list.  Typically the
-aggregated target value is simply the max or min of the request values held
-in the parameter list elements.
+A global list of CPU latency QoS requests is maintained along with an aggregated
+(effective) target value.  The aggregated target value is updated with changes
+to the request list or elements of the list.  For CPU latency QoS, the
+aggregated target value is simply the min of the request values held in the list
+elements.
+
 Note: the aggregated target value is implemented as an atomic variable so that
 reading the aggregated value does not require any locking mechanism.
 
+From kernel space the use of this interface is simple:
 
-From kernel mode the use of this interface is simple:
-
-void pm_qos_add_request(handle, param_class, target_value):
-  Will insert an element into the list for that identified PM QoS class with the
-  target value.  Upon change to this list the new target is recomputed and any
-  registered notifiers are called only if the target value is now different.
-  Clients of pm_qos need to save the returned handle for future use in other
-  pm_qos API functions.
+void cpu_latency_qos_add_request(handle, target_value):
+  Will insert an element into the CPU latency QoS list with the target value.
+  Upon change to this list the new target is recomputed and any registered
+  notifiers are called only if the target value is now different.
+  Clients of PM QoS need to save the returned handle for future use in other
+  PM QoS API functions.
 
-void pm_qos_update_request(handle, new_target_value):
+void cpu_latency_qos_update_request(handle, new_target_value):
   Will update the list element pointed to by the handle with the new target
   value and recompute the new aggregated target, calling the notification tree
   if the target is changed.
 
-void pm_qos_remove_request(handle):
+void cpu_latency_qos_remove_request(handle):
   Will remove the element.  After removal it will update the aggregate target
   and call the notification tree if the target was changed as a result of
   removing the request.
 
-int pm_qos_request(param_class):
-  Returns the aggregated value for a given PM QoS class.
+int cpu_latency_qos_limit():
+  Returns the aggregated value for the CPU latency QoS.
+
+int cpu_latency_qos_request_active(handle):
+  Returns if the request is still active, i.e. it has not been removed from the
+  CPU latency QoS list.
 
-int pm_qos_request_active(handle):
-  Returns if the request is still active, i.e. it has not been removed from a
-  PM QoS class constraints list.
+int cpu_latency_qos_add_notifier(notifier):
+  Adds a notification callback function to the CPU latency QoS. The callback is
+  called when the aggregated value for the CPU latency QoS is changed.
 
-int pm_qos_add_notifier(param_class, notifier):
-  Adds a notification callback function to the PM QoS class. The callback is
-  called when the aggregated value for the PM QoS class is changed.
+int cpu_latency_qos_remove_notifier(notifier):
+  Removes the notification callback function from the CPU latency QoS.
 
-int pm_qos_remove_notifier(int param_class, notifier):
-  Removes the notification callback function for the PM QoS class.
 
+From user space:
 
-From user mode:
+The infrastructure exposes one device node, /dev/cpu_dma_latency, for the CPU
+latency QoS.
 
-Only processes can register a pm_qos request.  To provide for automatic
+Only processes can register a PM QoS request.  To provide for automatic
 cleanup of a process, the interface requires the process to register its
-parameter requests in the following way:
+parameter requests as follows.
 
-To register the default pm_qos target for the specific parameter, the process
-must open /dev/cpu_dma_latency
+To register the default PM QoS target for the CPU latency QoS, the process must
+open /dev/cpu_dma_latency.
 
 As long as the device node is held open that process has a registered
 request on the parameter.
 
-To change the requested target value the process needs to write an s32 value to
-the open device node.  Alternatively the user mode program could write a hex
-string for the value using 10 char long format e.g. "0x12345678".  This
-translates to a pm_qos_update_request call.
+To change the requested target value, the process needs to write an s32 value to
+the open device node.  Alternatively, it can write a hex string for the value
+using the 10 char long format e.g. "0x12345678".  This translates to a
+cpu_latency_qos_update_request() call.
 
 To remove the user mode request for a target value simply close the device
 node.