Message-ID: <20070222135457.C26335@unix-os.sc.intel.com>
Date:	Thu, 22 Feb 2007 13:54:57 -0800
From:	Venkatesh Pallipadi <venkatesh.pallipadi@...el.com>
To:	linux-kernel <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...l.org>, Dave Jones <davej@...hat.com>,
	linux-acpi@...r.kernel.org
Cc:	Adam Belay <abelay@...ell.com>, Shaohua Li <shaohua.li@...el.com>,
	Len Brown <len.brown@...el.com>
Subject: [PATCH 3/3]cpuidle take2: Basic documentation for cpuidle



Documentation for cpuidle infrastructure

Signed-off-by: Venkatesh Pallipadi <venkatesh.pallipadi@...el.com>
Signed-off-by: Adam Belay <abelay@...ell.com>
Signed-off-by: Shaohua Li <shaohua.li@...el.com>

Index: linux-2.6.21-rc-mm/Documentation/cpuidle/core.txt
===================================================================
--- /dev/null
+++ linux-2.6.21-rc-mm/Documentation/cpuidle/core.txt
@@ -0,0 +1,17 @@
+
+		Supporting multiple CPU idle levels in kernel
+
+				cpuidle
+
+General Information:
+
+Various CPUs today support multiple idle levels that are differentiated
+by varying exit latencies and power consumption during idle.
+cpuidle is a generic in-kernel infrastructure that separates
+idle policy (governor) from idle mechanism (driver) and provides a
+standardized infrastructure to support independent development of
+governors and drivers.
+
+cpuidle resides under /drivers/cpuidle.
+
+
Index: linux-2.6.21-rc-mm/Documentation/cpuidle/driver.txt
===================================================================
--- /dev/null
+++ linux-2.6.21-rc-mm/Documentation/cpuidle/driver.txt
@@ -0,0 +1,24 @@
+
+
+		Supporting multiple CPU idle levels in kernel
+
+				cpuidle drivers
+
+
+
+
+cpuidle driver supports capability detection for a particular system. The
+init and exit routines will be called for each online CPU, with a percpu
+cpuidle_driver object and driver should fill in cpuidle_states inside
+cpuidle_driver depending on the CPU capability.
+
+Driver can handle dynamic state changes (like battery<->AC), by calling
+force_redetect interface.
+
+It is possible to have more than one driver registered at the same time and
+user can switch between drivers using /sysfs interface.
+
+Interfaces:
+int cpuidle_register_driver(struct cpuidle_driver *drv);
+void cpuidle_unregister_driver(struct cpuidle_driver *drv);
+int cpuidle_force_redetect(struct cpuidle_device *dev);
Index: linux-2.6.21-rc-mm/Documentation/cpuidle/sysfs.txt
===================================================================
--- /dev/null
+++ linux-2.6.21-rc-mm/Documentation/cpuidle/sysfs.txt
@@ -0,0 +1,27 @@
+
+
+		Supporting multiple CPU idle levels in kernel
+
+				cpuidle sysfs
+
+System global cpuidle information are under
+/sys/devices/system/cpu/cpuidle
+
+The current interfaces in this directory has self-explanatory names:
+* available_drivers
+* available_governors
+* current_driver
+* current_governor
+
+Per logical CPU specific cpuidle information are under
+/sys/devices/system/cpu/cpuX/cpuidle
+for each online cpu X
+
+Under this percpu directory, there is a directory for each idle state supported
+by the driver, which in turn has
+* latency
+* power
+* time
+* usage
+
+
Index: linux-2.6.21-rc-mm/Documentation/cpuidle/governor.txt
===================================================================
--- /dev/null
+++ linux-2.6.21-rc-mm/Documentation/cpuidle/governor.txt
@@ -0,0 +1,24 @@
+
+
+
+		Supporting multiple CPU idle levels in kernel
+
+				cpuidle governors
+
+
+
+
+cpuidle governor is policy routine that decides what idle state to enter at
+any given time. cpuidle core uses different callbacks to governor while
+handling idle entry.
+* select_state callback where governor can determine next idle state to enter
+* prepare_idle callback is called before entering an idle state
+* scan callback is called after a driver forces redetection of the states
+
+More than one governor can be registered at the same time and
+user can switch between drivers using /sysfs interface.
+
+Interfaces:
+int cpuidle_register_governor(struct cpuidle_governor *gov);
+void cpuidle_unregister_governor(struct cpuidle_governor *gov);
+
-
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