diff options
Diffstat (limited to 'Documentation/power')
| -rw-r--r-- | Documentation/power/opp.txt | 52 | ||||
| -rw-r--r-- | Documentation/power/pm_qos_interface.txt | 13 | ||||
| -rw-r--r-- | Documentation/power/runtime_pm.txt | 6 | ||||
| -rw-r--r-- | Documentation/power/states.txt | 6 |
4 files changed, 22 insertions, 55 deletions
diff --git a/Documentation/power/opp.txt b/Documentation/power/opp.txt index c6279c2be47c..0c007e250cd1 100644 --- a/Documentation/power/opp.txt +++ b/Documentation/power/opp.txt @@ -79,22 +79,6 @@ dependent subsystems such as cpufreq are left to the discretion of the SoC specific framework which uses the OPP library. Similar care needs to be taken care to refresh the cpufreq table in cases of these operations. -WARNING on OPP List locking mechanism: -------------------------------------------------- -OPP library uses RCU for exclusivity. RCU allows the query functions to operate -in multiple contexts and this synchronization mechanism is optimal for a read -intensive operations on data structure as the OPP library caters to. - -To ensure that the data retrieved are sane, the users such as SoC framework -should ensure that the section of code operating on OPP queries are locked -using RCU read locks. The opp_find_freq_{exact,ceil,floor}, -opp_get_{voltage, freq, opp_count} fall into this category. - -opp_{add,enable,disable} are updaters which use mutex and implement it's own -RCU locking mechanisms. These functions should *NOT* be called under RCU locks -and other contexts that prevent blocking functions in RCU or mutex operations -from working. - 2. Initial OPP List Registration ================================ The SoC implementation calls dev_pm_opp_add function iteratively to add OPPs per @@ -137,15 +121,18 @@ functions return the matching pointer representing the opp if a match is found, else returns error. These errors are expected to be handled by standard error checks such as IS_ERR() and appropriate actions taken by the caller. +Callers of these functions shall call dev_pm_opp_put() after they have used the +OPP. Otherwise the memory for the OPP will never get freed and result in +memleak. + dev_pm_opp_find_freq_exact - Search for an OPP based on an *exact* frequency and availability. This function is especially useful to enable an OPP which is not available by default. Example: In a case when SoC framework detects a situation where a higher frequency could be made available, it can use this function to find the OPP prior to call the dev_pm_opp_enable to actually make it available. - rcu_read_lock(); opp = dev_pm_opp_find_freq_exact(dev, 1000000000, false); - rcu_read_unlock(); + dev_pm_opp_put(opp); /* dont operate on the pointer.. just do a sanity check.. */ if (IS_ERR(opp)) { pr_err("frequency not disabled!\n"); @@ -163,9 +150,8 @@ dev_pm_opp_find_freq_floor - Search for an available OPP which is *at most* the frequency. Example: To find the highest opp for a device: freq = ULONG_MAX; - rcu_read_lock(); - dev_pm_opp_find_freq_floor(dev, &freq); - rcu_read_unlock(); + opp = dev_pm_opp_find_freq_floor(dev, &freq); + dev_pm_opp_put(opp); dev_pm_opp_find_freq_ceil - Search for an available OPP which is *at least* the provided frequency. This function is useful while searching for a @@ -173,17 +159,15 @@ dev_pm_opp_find_freq_ceil - Search for an available OPP which is *at least* the frequency. Example 1: To find the lowest opp for a device: freq = 0; - rcu_read_lock(); - dev_pm_opp_find_freq_ceil(dev, &freq); - rcu_read_unlock(); + opp = dev_pm_opp_find_freq_ceil(dev, &freq); + dev_pm_opp_put(opp); Example 2: A simplified implementation of a SoC cpufreq_driver->target: soc_cpufreq_target(..) { /* Do stuff like policy checks etc. */ /* Find the best frequency match for the req */ - rcu_read_lock(); opp = dev_pm_opp_find_freq_ceil(dev, &freq); - rcu_read_unlock(); + dev_pm_opp_put(opp); if (!IS_ERR(opp)) soc_switch_to_freq_voltage(freq); else @@ -208,9 +192,8 @@ dev_pm_opp_enable - Make a OPP available for operation. implementation might choose to do something as follows: if (cur_temp < temp_low_thresh) { /* Enable 1GHz if it was disabled */ - rcu_read_lock(); opp = dev_pm_opp_find_freq_exact(dev, 1000000000, false); - rcu_read_unlock(); + dev_pm_opp_put(opp); /* just error check */ if (!IS_ERR(opp)) ret = dev_pm_opp_enable(dev, 1000000000); @@ -224,9 +207,8 @@ dev_pm_opp_disable - Make an OPP to be not available for operation choose to do something as follows: if (cur_temp > temp_high_thresh) { /* Disable 1GHz if it was enabled */ - rcu_read_lock(); opp = dev_pm_opp_find_freq_exact(dev, 1000000000, true); - rcu_read_unlock(); + dev_pm_opp_put(opp); /* just error check */ if (!IS_ERR(opp)) ret = dev_pm_opp_disable(dev, 1000000000); @@ -249,10 +231,9 @@ dev_pm_opp_get_voltage - Retrieve the voltage represented by the opp pointer. soc_switch_to_freq_voltage(freq) { /* do things */ - rcu_read_lock(); opp = dev_pm_opp_find_freq_ceil(dev, &freq); v = dev_pm_opp_get_voltage(opp); - rcu_read_unlock(); + dev_pm_opp_put(opp); if (v) regulator_set_voltage(.., v); /* do other things */ @@ -266,12 +247,12 @@ dev_pm_opp_get_freq - Retrieve the freq represented by the opp pointer. { /* do things.. */ max_freq = ULONG_MAX; - rcu_read_lock(); max_opp = dev_pm_opp_find_freq_floor(dev,&max_freq); requested_opp = dev_pm_opp_find_freq_ceil(dev,&freq); if (!IS_ERR(max_opp) && !IS_ERR(requested_opp)) r = soc_test_validity(max_opp, requested_opp); - rcu_read_unlock(); + dev_pm_opp_put(max_opp); + dev_pm_opp_put(requested_opp); /* do other things */ } soc_test_validity(..) @@ -289,7 +270,6 @@ dev_pm_opp_get_opp_count - Retrieve the number of available opps for a device soc_notify_coproc_available_frequencies() { /* Do things */ - rcu_read_lock(); num_available = dev_pm_opp_get_opp_count(dev); speeds = kzalloc(sizeof(u32) * num_available, GFP_KERNEL); /* populate the table in increasing order */ @@ -298,8 +278,8 @@ dev_pm_opp_get_opp_count - Retrieve the number of available opps for a device speeds[i] = freq; freq++; i++; + dev_pm_opp_put(opp); } - rcu_read_unlock(); soc_notify_coproc(AVAILABLE_FREQs, speeds, num_available); /* Do other things */ diff --git a/Documentation/power/pm_qos_interface.txt b/Documentation/power/pm_qos_interface.txt index 129f7c0e1483..21d2d48f87a2 100644 --- a/Documentation/power/pm_qos_interface.txt +++ b/Documentation/power/pm_qos_interface.txt @@ -163,8 +163,7 @@ of flags and remove sysfs attributes pm_qos_no_power_off and pm_qos_remote_wakeu under the device's power directory. Notification mechanisms: -The per-device PM QoS framework has 2 different and distinct notification trees: -a per-device notification tree and a global notification tree. +The per-device PM QoS framework has a per-device notification tree. int dev_pm_qos_add_notifier(device, notifier): Adds a notification callback function for the device. @@ -174,16 +173,6 @@ is changed (for resume latency device PM QoS only). int dev_pm_qos_remove_notifier(device, notifier): Removes the notification callback function for the device. -int dev_pm_qos_add_global_notifier(notifier): -Adds a notification callback function in the global notification tree of the -framework. -The callback is called when the aggregated value for any device is changed -(for resume latency device PM QoS only). - -int dev_pm_qos_remove_global_notifier(notifier): -Removes the notification callback function from the global notification tree -of the framework. - Active state latency tolerance diff --git a/Documentation/power/runtime_pm.txt b/Documentation/power/runtime_pm.txt index 4870980e967e..64546eb9a16a 100644 --- a/Documentation/power/runtime_pm.txt +++ b/Documentation/power/runtime_pm.txt @@ -100,7 +100,7 @@ knows what to do to handle the device). * If the suspend callback returns an error code different from -EBUSY and -EAGAIN, the PM core regards this as a fatal error and will refuse to run the helper functions described in Section 4 for the device until its status - is directly set to either'active', or 'suspended' (the PM core provides + is directly set to either 'active', or 'suspended' (the PM core provides special helper functions for this purpose). In particular, if the driver requires remote wakeup capability (i.e. hardware @@ -217,7 +217,7 @@ defined in include/linux/pm.h: one to complete spinlock_t lock; - - lock used for synchronisation + - lock used for synchronization atomic_t usage_count; - the usage counter of the device @@ -565,7 +565,7 @@ appropriate to ensure that the device is not put back to sleep during the probe. This can happen with systems such as the network device layer. It may be desirable to suspend the device once ->probe() has finished. -Therefore the driver core uses the asyncronous pm_request_idle() to submit a +Therefore the driver core uses the asynchronous pm_request_idle() to submit a request to execute the subsystem-level idle callback for the device at that time. A driver that makes use of the runtime autosuspend feature, may want to update the last busy mark before returning from ->probe(). diff --git a/Documentation/power/states.txt b/Documentation/power/states.txt index 8a39ce45d8a0..bc4548245a24 100644 --- a/Documentation/power/states.txt +++ b/Documentation/power/states.txt @@ -25,7 +25,7 @@ to be used subsequently to change to the one represented by that string. Consequently, there are two ways to cause the system to go into the Suspend-To-Idle sleep state. The first one is to write "freeze" directly to /sys/power/state. The second one is to write "s2idle" to /sys/power/mem_sleep -and then to wrtie "mem" to /sys/power/state. Similarly, there are two ways +and then to write "mem" to /sys/power/state. Similarly, there are two ways to cause the system to go into the Power-On Suspend sleep state (the strings to write to the control files in that case are "standby" or "shallow" and "mem", respectively) if that state is supported by the platform. In turn, there is @@ -35,9 +35,7 @@ only one way to cause the system to go into the Suspend-To-RAM state (write The default suspend mode (ie. the one to be used without writing anything into /sys/power/mem_sleep) is either "deep" (if Suspend-To-RAM is supported) or "s2idle", but it can be overridden by the value of the "mem_sleep_default" -parameter in the kernel command line. On some ACPI-based systems, depending on -the information in the FADT, the default may be "s2idle" even if Suspend-To-RAM -is supported. +parameter in the kernel command line. The properties of all of the sleep states are described below. |