1 ===============
2 Charger Manager
3 ===============
4
5 (C) 2011 MyungJoo Ham <myungjoo.ham@samsung.com>, GPL
6
7 Charger Manager provides in-kernel battery charger management that
8 requires temperature monitoring during suspend-to-RAM state
9 and where each battery may have multiple chargers attached and the userland
10 wants to look at the aggregated information of the multiple chargers.
11
12 Charger Manager is a platform_driver with power-supply-class entries.
13 An instance of Charger Manager (a platform-device created with Charger-Manager)
14 represents an independent battery with chargers. If there are multiple
15 batteries with their own chargers acting independently in a system,
16 the system may need multiple instances of Charger Manager.
17
18 1. Introduction
19 ===============
20
21 Charger Manager supports the following:
22
23 * Support for multiple chargers (e.g., a device with USB, AC, and solar panels)
24 A system may have multiple chargers (or power sources) and some of
25 they may be activated at the same time. Each charger may have its
26 own power-supply-class and each power-supply-class can provide
27 different information about the battery status. This framework
28 aggregates charger-related information from multiple sources and
29 shows combined information as a single power-supply-class.
30
31 * Support for in suspend-to-RAM polling (with suspend_again callback)
32 While the battery is being charged and the system is in suspend-to-RAM,
33 we may need to monitor the battery health by looking at the ambient or
34 battery temperature. We can accomplish this by waking up the system
35 periodically. However, such a method wakes up devices unnecessarily for
36 monitoring the battery health and tasks, and user processes that are
37 supposed to be kept suspended. That, in turn, incurs unnecessary power
38 consumption and slow down charging process. Or even, such peak power
39 consumption can stop chargers in the middle of charging
40 (external power input < device power consumption), which not
41 only affects the charging time, but the lifespan of the battery.
42
43 Charger Manager provides a function "cm_suspend_again" that can be
44 used as suspend_again callback of platform_suspend_ops. If the platform
45 requires tasks other than cm_suspend_again, it may implement its own
46 suspend_again callback that calls cm_suspend_again in the middle.
47 Normally, the platform will need to resume and suspend some devices
48 that are used by Charger Manager.
49
50 * Support for premature full-battery event handling
51 If the battery voltage drops by "fullbatt_vchkdrop_uV" after
52 "fullbatt_vchkdrop_ms" from the full-battery event, the framework
53 restarts charging. This check is also performed while suspended by
54 setting wakeup time accordingly and using suspend_again.
55
56 * Support for uevent-notify
57 With the charger-related events, the device sends
58 notification to users with UEVENT.
59
60 2. Global Charger-Manager Data related with suspend_again
61 =========================================================
62 In order to setup Charger Manager with suspend-again feature
63 (in-suspend monitoring), the user should provide charger_global_desc
64 with setup_charger_manager(`struct charger_global_desc *`).
65 This charger_global_desc data for in-suspend monitoring is global
66 as the name suggests. Thus, the user needs to provide only once even
67 if there are multiple batteries. If there are multiple batteries, the
68 multiple instances of Charger Manager share the same charger_global_desc
69 and it will manage in-suspend monitoring for all instances of Charger Manager.
70
71 The user needs to provide all the three entries to `struct charger_global_desc`
72 properly in order to activate in-suspend monitoring:
73
74 `char *rtc_name;`
75 The name of rtc (e.g., "rtc0") used to wakeup the system from
76 suspend for Charger Manager. The alarm interrupt (AIE) of the rtc
77 should be able to wake up the system from suspend. Charger Manager
78 saves and restores the alarm value and use the previously-defined
79 alarm if it is going to go off earlier than Charger Manager so that
80 Charger Manager does not interfere with previously-defined alarms.
81
82 `bool (*rtc_only_wakeup)(void);`
83 This callback should let CM know whether
84 the wakeup-from-suspend is caused only by the alarm of "rtc" in the
85 same struct. If there is any other wakeup source triggered the
86 wakeup, it should return false. If the "rtc" is the only wakeup
87 reason, it should return true.
88
89 `bool assume_timer_stops_in_suspend;`
90 if true, Charger Manager assumes that
91 the timer (CM uses jiffies as timer) stops during suspend. Then, CM
92 assumes that the suspend-duration is same as the alarm length.
93
94
95 3. How to setup suspend_again
96 =============================
97 Charger Manager provides a function "extern bool cm_suspend_again(void)".
98 When cm_suspend_again is called, it monitors every battery. The suspend_ops
99 callback of the system's platform_suspend_ops can call cm_suspend_again
100 function to know whether Charger Manager wants to suspend again or not.
101 If there are no other devices or tasks that want to use suspend_again
102 feature, the platform_suspend_ops may directly refer to cm_suspend_again
103 for its suspend_again callback.
104
105 The cm_suspend_again() returns true (meaning "I want to suspend again")
106 if the system was woken up by Charger Manager and the polling
107 (in-suspend monitoring) results in "normal".
108
109 4. Charger-Manager Data (struct charger_desc)
110 =============================================
111 For each battery charged independently from other batteries (if a series of
112 batteries are charged by a single charger, they are counted as one independent
113 battery), an instance of Charger Manager is attached to it. The following
114
115 struct charger_desc elements:
116
117 `char *psy_name;`
118 The power-supply-class name of the battery. Default is
119 "battery" if psy_name is NULL. Users can access the psy entries
120 at "/sys/class/power_supply/[psy_name]/".
121
122 `enum polling_modes polling_mode;`
123 CM_POLL_DISABLE:
124 do not poll this battery.
125 CM_POLL_ALWAYS:
126 always poll this battery.
127 CM_POLL_EXTERNAL_POWER_ONLY:
128 poll this battery if and only if an external power
129 source is attached.
130 CM_POLL_CHARGING_ONLY:
131 poll this battery if and only if the battery is being charged.
132
133 `unsigned int fullbatt_vchkdrop_ms; / unsigned int fullbatt_vchkdrop_uV;`
134 If both have non-zero values, Charger Manager will check the
135 battery voltage drop fullbatt_vchkdrop_ms after the battery is fully
136 charged. If the voltage drop is over fullbatt_vchkdrop_uV, Charger
137 Manager will try to recharge the battery by disabling and enabling
138 chargers. Recharge with voltage drop condition only (without delay
139 condition) is needed to be implemented with hardware interrupts from
140 fuel gauges or charger devices/chips.
141
142 `unsigned int fullbatt_uV;`
143 If specified with a non-zero value, Charger Manager assumes
144 that the battery is full (capacity = 100) if the battery is not being
145 charged and the battery voltage is equal to or greater than
146 fullbatt_uV.
147
148 `unsigned int polling_interval_ms;`
149 Required polling interval in ms. Charger Manager will poll
150 this battery every polling_interval_ms or more frequently.
151
152 `enum data_source battery_present;`
153 CM_BATTERY_PRESENT:
154 assume that the battery exists.
155 CM_NO_BATTERY:
156 assume that the battery does not exists.
157 CM_FUEL_GAUGE:
158 get battery presence information from fuel gauge.
159 CM_CHARGER_STAT:
160 get battery presence from chargers.
161
162 `char **psy_charger_stat;`
163 An array ending with NULL that has power-supply-class names of
164 chargers. Each power-supply-class should provide "PRESENT" (if
165 battery_present is "CM_CHARGER_STAT"), "ONLINE" (shows whether an
166 external power source is attached or not), and "STATUS" (shows whether
167 the battery is {"FULL" or not FULL} or {"FULL", "Charging",
168 "Discharging", "NotCharging"}).
169
170 `int num_charger_regulators; / struct regulator_bulk_data *charger_regulators;`
171 Regulators representing the chargers in the form for
172 regulator framework's bulk functions.
173
174 `char *psy_fuel_gauge;`
175 Power-supply-class name of the fuel gauge.
176
177 `int (*temperature_out_of_range)(int *mC); / bool measure_battery_temp;`
178 This callback returns 0 if the temperature is safe for charging,
179 a positive number if it is too hot to charge, and a negative number
180 if it is too cold to charge. With the variable mC, the callback returns
181 the temperature in 1/1000 of centigrade.
182 The source of temperature can be battery or ambient one according to
183 the value of measure_battery_temp.
184
185
186 5. Notify Charger-Manager of charger events: cm_notify_event()
187 ==============================================================
188 If there is an charger event is required to notify
189 Charger Manager, a charger device driver that triggers the event can call
190 cm_notify_event(psy, type, msg) to notify the corresponding Charger Manager.
191 In the function, psy is the charger driver's power_supply pointer, which is
192 associated with Charger-Manager. The parameter "type"
193 is the same as irq's type (enum cm_event_types). The event message "msg" is
194 optional and is effective only if the event type is "UNDESCRIBED" or "OTHERS".
195
196 6. Other Considerations
197 =======================
198
199 At the charger/battery-related events such as battery-pulled-out,
200 charger-pulled-out, charger-inserted, DCIN-over/under-voltage, charger-stopped,
201 and others critical to chargers, the system should be configured to wake up.
202 At least the following should wake up the system from a suspend:
203 a) charger-on/off b) external-power-in/out c) battery-in/out (while charging)
204
205 It is usually accomplished by configuring the PMIC as a wakeup source.
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