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1 | Charger Manager | ||
2 | (C) 2011 MyungJoo Ham <myungjoo.ham@samsung.com>, GPL | ||
3 | |||
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. | ||
8 | |||
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. | ||
14 | |||
15 | 1. Introduction | ||
16 | =============== | ||
17 | |||
18 | Charger Manager supports the following: | ||
19 | |||
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. | ||
27 | |||
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 unncessary 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. | ||
39 | |||
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. | ||
46 | |||
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. | ||
52 | |||
53 | * Support for uevent-notify | ||
54 | With the charger-related events, the device sends | ||
55 | notification to users with UEVENT. | ||
56 | |||
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. | ||
67 | |||
68 | The user needs to provide all the three entries properly in order to activate | ||
69 | in-suspend monitoring: | ||
70 | |||
71 | struct charger_global_desc { | ||
72 | |||
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. | ||
80 | |||
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. | ||
87 | |||
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 | }; | ||
93 | |||
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. | ||
103 | |||
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". | ||
107 | |||
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. | ||
113 | |||
114 | struct charger_desc { | ||
115 | |||
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]/". | ||
120 | |||
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. | ||
128 | |||
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. | ||
138 | |||
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. | ||
144 | |||
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. | ||
148 | |||
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. | ||
154 | |||
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"}). | ||
162 | |||
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. | ||
167 | |||
168 | char *psy_fuel_gauge; | ||
169 | : Power-supply-class name of the fuel gauge. | ||
170 | |||
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 | }; | ||
180 | |||
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". | ||
190 | |||
191 | 6. Other Considerations | ||
192 | ======================= | ||
193 | |||
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) | ||
199 | |||
200 | It is usually accomplished by configuring the PMIC as a wakeup source. | ||