206 lines
9.3 KiB
ReStructuredText
206 lines
9.3 KiB
ReStructuredText
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===============
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Charger Manager
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===============
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(C) 2011 MyungJoo Ham <myungjoo.ham@samsung.com>, GPL
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Charger Manager provides in-kernel battery charger management that
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requires temperature monitoring during suspend-to-RAM state
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and where each battery may have multiple chargers attached and the userland
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wants to look at the aggregated information of the multiple chargers.
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Charger Manager is a platform_driver with power-supply-class entries.
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An instance of Charger Manager (a platform-device created with Charger-Manager)
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represents an independent battery with chargers. If there are multiple
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batteries with their own chargers acting independently in a system,
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the system may need multiple instances of Charger Manager.
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1. Introduction
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===============
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Charger Manager supports the following:
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* Support for multiple chargers (e.g., a device with USB, AC, and solar panels)
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A system may have multiple chargers (or power sources) and some of
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they may be activated at the same time. Each charger may have its
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own power-supply-class and each power-supply-class can provide
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different information about the battery status. This framework
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aggregates charger-related information from multiple sources and
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shows combined information as a single power-supply-class.
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* Support for in suspend-to-RAM polling (with suspend_again callback)
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While the battery is being charged and the system is in suspend-to-RAM,
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we may need to monitor the battery health by looking at the ambient or
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battery temperature. We can accomplish this by waking up the system
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periodically. However, such a method wakes up devices unnecessarily for
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monitoring the battery health and tasks, and user processes that are
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supposed to be kept suspended. That, in turn, incurs unnecessary power
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consumption and slow down charging process. Or even, such peak power
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consumption can stop chargers in the middle of charging
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(external power input < device power consumption), which not
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only affects the charging time, but the lifespan of the battery.
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Charger Manager provides a function "cm_suspend_again" that can be
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used as suspend_again callback of platform_suspend_ops. If the platform
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requires tasks other than cm_suspend_again, it may implement its own
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suspend_again callback that calls cm_suspend_again in the middle.
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Normally, the platform will need to resume and suspend some devices
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that are used by Charger Manager.
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* Support for premature full-battery event handling
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If the battery voltage drops by "fullbatt_vchkdrop_uV" after
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"fullbatt_vchkdrop_ms" from the full-battery event, the framework
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restarts charging. This check is also performed while suspended by
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setting wakeup time accordingly and using suspend_again.
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* Support for uevent-notify
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With the charger-related events, the device sends
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notification to users with UEVENT.
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2. Global Charger-Manager Data related with suspend_again
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=========================================================
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In order to setup Charger Manager with suspend-again feature
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(in-suspend monitoring), the user should provide charger_global_desc
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with setup_charger_manager(`struct charger_global_desc *`).
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This charger_global_desc data for in-suspend monitoring is global
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as the name suggests. Thus, the user needs to provide only once even
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if there are multiple batteries. If there are multiple batteries, the
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multiple instances of Charger Manager share the same charger_global_desc
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and it will manage in-suspend monitoring for all instances of Charger Manager.
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The user needs to provide all the three entries to `struct charger_global_desc`
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properly in order to activate in-suspend monitoring:
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`char *rtc_name;`
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The name of rtc (e.g., "rtc0") used to wakeup the system from
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suspend for Charger Manager. The alarm interrupt (AIE) of the rtc
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should be able to wake up the system from suspend. Charger Manager
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saves and restores the alarm value and use the previously-defined
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alarm if it is going to go off earlier than Charger Manager so that
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Charger Manager does not interfere with previously-defined alarms.
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`bool (*rtc_only_wakeup)(void);`
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This callback should let CM know whether
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the wakeup-from-suspend is caused only by the alarm of "rtc" in the
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same struct. If there is any other wakeup source triggered the
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wakeup, it should return false. If the "rtc" is the only wakeup
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reason, it should return true.
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`bool assume_timer_stops_in_suspend;`
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if true, Charger Manager assumes that
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the timer (CM uses jiffies as timer) stops during suspend. Then, CM
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assumes that the suspend-duration is same as the alarm length.
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3. How to setup suspend_again
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=============================
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Charger Manager provides a function "extern bool cm_suspend_again(void)".
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When cm_suspend_again is called, it monitors every battery. The suspend_ops
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callback of the system's platform_suspend_ops can call cm_suspend_again
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function to know whether Charger Manager wants to suspend again or not.
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If there are no other devices or tasks that want to use suspend_again
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feature, the platform_suspend_ops may directly refer to cm_suspend_again
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for its suspend_again callback.
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The cm_suspend_again() returns true (meaning "I want to suspend again")
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if the system was woken up by Charger Manager and the polling
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(in-suspend monitoring) results in "normal".
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4. Charger-Manager Data (struct charger_desc)
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=============================================
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For each battery charged independently from other batteries (if a series of
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batteries are charged by a single charger, they are counted as one independent
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battery), an instance of Charger Manager is attached to it. The following
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struct charger_desc elements:
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`char *psy_name;`
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The power-supply-class name of the battery. Default is
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"battery" if psy_name is NULL. Users can access the psy entries
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at "/sys/class/power_supply/[psy_name]/".
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`enum polling_modes polling_mode;`
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CM_POLL_DISABLE:
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do not poll this battery.
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CM_POLL_ALWAYS:
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always poll this battery.
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CM_POLL_EXTERNAL_POWER_ONLY:
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poll this battery if and only if an external power
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source is attached.
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CM_POLL_CHARGING_ONLY:
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poll this battery if and only if the battery is being charged.
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`unsigned int fullbatt_vchkdrop_ms; / unsigned int fullbatt_vchkdrop_uV;`
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If both have non-zero values, Charger Manager will check the
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battery voltage drop fullbatt_vchkdrop_ms after the battery is fully
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charged. If the voltage drop is over fullbatt_vchkdrop_uV, Charger
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Manager will try to recharge the battery by disabling and enabling
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chargers. Recharge with voltage drop condition only (without delay
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condition) is needed to be implemented with hardware interrupts from
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fuel gauges or charger devices/chips.
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`unsigned int fullbatt_uV;`
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If specified with a non-zero value, Charger Manager assumes
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that the battery is full (capacity = 100) if the battery is not being
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charged and the battery voltage is equal to or greater than
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fullbatt_uV.
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`unsigned int polling_interval_ms;`
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Required polling interval in ms. Charger Manager will poll
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this battery every polling_interval_ms or more frequently.
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`enum data_source battery_present;`
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CM_BATTERY_PRESENT:
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assume that the battery exists.
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CM_NO_BATTERY:
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assume that the battery does not exists.
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CM_FUEL_GAUGE:
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get battery presence information from fuel gauge.
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CM_CHARGER_STAT:
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get battery presence from chargers.
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`char **psy_charger_stat;`
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An array ending with NULL that has power-supply-class names of
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chargers. Each power-supply-class should provide "PRESENT" (if
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battery_present is "CM_CHARGER_STAT"), "ONLINE" (shows whether an
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external power source is attached or not), and "STATUS" (shows whether
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the battery is {"FULL" or not FULL} or {"FULL", "Charging",
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"Discharging", "NotCharging"}).
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`int num_charger_regulators; / struct regulator_bulk_data *charger_regulators;`
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Regulators representing the chargers in the form for
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regulator framework's bulk functions.
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`char *psy_fuel_gauge;`
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Power-supply-class name of the fuel gauge.
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`int (*temperature_out_of_range)(int *mC); / bool measure_battery_temp;`
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This callback returns 0 if the temperature is safe for charging,
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a positive number if it is too hot to charge, and a negative number
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if it is too cold to charge. With the variable mC, the callback returns
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the temperature in 1/1000 of centigrade.
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The source of temperature can be battery or ambient one according to
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the value of measure_battery_temp.
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5. Notify Charger-Manager of charger events: cm_notify_event()
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==============================================================
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If there is an charger event is required to notify
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Charger Manager, a charger device driver that triggers the event can call
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cm_notify_event(psy, type, msg) to notify the corresponding Charger Manager.
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In the function, psy is the charger driver's power_supply pointer, which is
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associated with Charger-Manager. The parameter "type"
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is the same as irq's type (enum cm_event_types). The event message "msg" is
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optional and is effective only if the event type is "UNDESCRIBED" or "OTHERS".
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6. Other Considerations
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=======================
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At the charger/battery-related events such as battery-pulled-out,
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charger-pulled-out, charger-inserted, DCIN-over/under-voltage, charger-stopped,
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and others critical to chargers, the system should be configured to wake up.
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At least the following should wake up the system from a suspend:
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a) charger-on/off b) external-power-in/out c) battery-in/out (while charging)
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It is usually accomplished by configuring the PMIC as a wakeup source.
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