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1 Charger Manager
2 (C) 2011 MyungJoo Ham <myungjoo.ham@samsung.com>, GPL
4 Charger Manager provides in-kernel battery charger management that
5 requires temperature monitoring during suspend-to-RAM state
6 and where each battery may have multiple chargers attached and the userland
7 wants to look at the aggregated information of the multiple chargers.
9 Charger Manager is a platform_driver with power-supply-class entries.
10 An instance of Charger Manager (a platform-device created with Charger-Manager)
11 represents an independent battery with chargers. If there are multiple
12 batteries with their own chargers acting independently in a system,
13 the system may need multiple instances of Charger Manager.
15 1. Introduction
16 ===============
18 Charger Manager supports the following:
20 * Support for multiple chargers (e.g., a device with USB, AC, and solar panels)
21 A system may have multiple chargers (or power sources) and some of
22 they may be activated at the same time. Each charger may have its
23 own power-supply-class and each power-supply-class can provide
24 different information about the battery status. This framework
25 aggregates charger-related information from multiple sources and
26 shows combined information as a single power-supply-class.
28 * Support for in suspend-to-RAM polling (with suspend_again callback)
29 While the battery is being charged and the system is in suspend-to-RAM,
30 we may need to monitor the battery health by looking at the ambient or
31 battery temperature. We can accomplish this by waking up the system
32 periodically. However, such a method wakes up devices unnecessarily for
33 monitoring the battery health and tasks, and user processes that are
34 supposed to be kept suspended. That, in turn, incurs unnecessary power
35 consumption and slow down charging process. Or even, such peak power
36 consumption can stop chargers in the middle of charging
37 (external power input < device power consumption), which not
38 only affects the charging time, but the lifespan of the battery.
40 Charger Manager provides a function "cm_suspend_again" that can be
41 used as suspend_again callback of platform_suspend_ops. If the platform
42 requires tasks other than cm_suspend_again, it may implement its own
43 suspend_again callback that calls cm_suspend_again in the middle.
44 Normally, the platform will need to resume and suspend some devices
45 that are used by Charger Manager.
47 * Support for premature full-battery event handling
48 If the battery voltage drops by "fullbatt_vchkdrop_uV" after
49 "fullbatt_vchkdrop_ms" from the full-battery event, the framework
50 restarts charging. This check is also performed while suspended by
51 setting wakeup time accordingly and using suspend_again.
53 * Support for uevent-notify
54 With the charger-related events, the device sends
55 notification to users with UEVENT.
57 2. Global Charger-Manager Data related with suspend_again
58 ========================================================
59 In order to setup Charger Manager with suspend-again feature
60 (in-suspend monitoring), the user should provide charger_global_desc
61 with setup_charger_manager(struct charger_global_desc *).
62 This charger_global_desc data for in-suspend monitoring is global
63 as the name suggests. Thus, the user needs to provide only once even
64 if there are multiple batteries. If there are multiple batteries, the
65 multiple instances of Charger Manager share the same charger_global_desc
66 and it will manage in-suspend monitoring for all instances of Charger Manager.
68 The user needs to provide all the three entries properly in order to activate
69 in-suspend monitoring:
71 struct charger_global_desc {
73 char *rtc_name;
74 : The name of rtc (e.g., "rtc0") used to wakeup the system from
75 suspend for Charger Manager. The alarm interrupt (AIE) of the rtc
76 should be able to wake up the system from suspend. Charger Manager
77 saves and restores the alarm value and use the previously-defined
78 alarm if it is going to go off earlier than Charger Manager so that
79 Charger Manager does not interfere with previously-defined alarms.
81 bool (*rtc_only_wakeup)(void);
82 : This callback should let CM know whether
83 the wakeup-from-suspend is caused only by the alarm of "rtc" in the
84 same struct. If there is any other wakeup source triggered the
85 wakeup, it should return false. If the "rtc" is the only wakeup
86 reason, it should return true.
88 bool assume_timer_stops_in_suspend;
89 : if true, Charger Manager assumes that
90 the timer (CM uses jiffies as timer) stops during suspend. Then, CM
91 assumes that the suspend-duration is same as the alarm length.
92 };
94 3. How to setup suspend_again
95 =============================
96 Charger Manager provides a function "extern bool cm_suspend_again(void)".
97 When cm_suspend_again is called, it monitors every battery. The suspend_ops
98 callback of the system's platform_suspend_ops can call cm_suspend_again
99 function to know whether Charger Manager wants to suspend again or not.
100 If there are no other devices or tasks that want to use suspend_again
101 feature, the platform_suspend_ops may directly refer to cm_suspend_again
102 for its suspend_again callback.
104 The cm_suspend_again() returns true (meaning "I want to suspend again")
105 if the system was woken up by Charger Manager and the polling
106 (in-suspend monitoring) results in "normal".
108 4. Charger-Manager Data (struct charger_desc)
109 =============================================
110 For each battery charged independently from other batteries (if a series of
111 batteries are charged by a single charger, they are counted as one independent
112 battery), an instance of Charger Manager is attached to it.
114 struct charger_desc {
116 char *psy_name;
117 : The power-supply-class name of the battery. Default is
118 "battery" if psy_name is NULL. Users can access the psy entries
119 at "/sys/class/power_supply/[psy_name]/".
121 enum polling_modes polling_mode;
122 : CM_POLL_DISABLE: do not poll this battery.
123 CM_POLL_ALWAYS: always poll this battery.
124 CM_POLL_EXTERNAL_POWER_ONLY: poll this battery if and only if
125 an external power source is attached.
126 CM_POLL_CHARGING_ONLY: poll this battery if and only if the
127 battery is being charged.
129 unsigned int fullbatt_vchkdrop_ms;
130 unsigned int fullbatt_vchkdrop_uV;
131 : If both have non-zero values, Charger Manager will check the
132 battery voltage drop fullbatt_vchkdrop_ms after the battery is fully
133 charged. If the voltage drop is over fullbatt_vchkdrop_uV, Charger
134 Manager will try to recharge the battery by disabling and enabling
135 chargers. Recharge with voltage drop condition only (without delay
136 condition) is needed to be implemented with hardware interrupts from
137 fuel gauges or charger devices/chips.
139 unsigned int fullbatt_uV;
140 : If specified with a non-zero value, Charger Manager assumes
141 that the battery is full (capacity = 100) if the battery is not being
142 charged and the battery voltage is equal to or greater than
143 fullbatt_uV.
145 unsigned int polling_interval_ms;
146 : Required polling interval in ms. Charger Manager will poll
147 this battery every polling_interval_ms or more frequently.
149 enum data_source battery_present;
150 : CM_BATTERY_PRESENT: assume that the battery exists.
151 CM_NO_BATTERY: assume that the battery does not exists.
152 CM_FUEL_GAUGE: get battery presence information from fuel gauge.
153 CM_CHARGER_STAT: get battery presence from chargers.
155 char **psy_charger_stat;
156 : An array ending with NULL that has power-supply-class names of
157 chargers. Each power-supply-class should provide "PRESENT" (if
158 battery_present is "CM_CHARGER_STAT"), "ONLINE" (shows whether an
159 external power source is attached or not), and "STATUS" (shows whether
160 the battery is {"FULL" or not FULL} or {"FULL", "Charging",
161 "Discharging", "NotCharging"}).
163 int num_charger_regulators;
164 struct regulator_bulk_data *charger_regulators;
165 : Regulators representing the chargers in the form for
166 regulator framework's bulk functions.
168 char *psy_fuel_gauge;
169 : Power-supply-class name of the fuel gauge.
171 int (*temperature_out_of_range)(int *mC);
172 bool measure_battery_temp;
173 : This callback returns 0 if the temperature is safe for charging,
174 a positive number if it is too hot to charge, and a negative number
175 if it is too cold to charge. With the variable mC, the callback returns
176 the temperature in 1/1000 of centigrade.
177 The source of temperature can be battery or ambient one according to
178 the value of measure_battery_temp.
179 };
181 5. Notify Charger-Manager of charger events: cm_notify_event()
182 =========================================================
183 If there is an charger event is required to notify
184 Charger Manager, a charger device driver that triggers the event can call
185 cm_notify_event(psy, type, msg) to notify the corresponding Charger Manager.
186 In the function, psy is the charger driver's power_supply pointer, which is
187 associated with Charger-Manager. The parameter "type"
188 is the same as irq's type (enum cm_event_types). The event message "msg" is
189 optional and is effective only if the event type is "UNDESCRIBED" or "OTHERS".
191 6. Other Considerations
192 =======================
194 At the charger/battery-related events such as battery-pulled-out,
195 charger-pulled-out, charger-inserted, DCIN-over/under-voltage, charger-stopped,
196 and others critical to chargers, the system should be configured to wake up.
197 At least the following should wake up the system from a suspend:
198 a) charger-on/off b) external-power-in/out c) battery-in/out (while charging)
200 It is usually accomplished by configuring the PMIC as a wakeup source.