2 # (C) Copyright 2014-2015 Samsung Electronics
3 # Przemyslaw Marczak <p.marczak@samsung.com>
5 # SPDX-License-Identifier: GPL-2.0+
8 PMIC framework based on Driver Model
9 ====================================
18 This is an introduction to driver-model multi uclass PMIC IC's support.
19 At present it's based on two uclass types:
20 - UCLASS_PMIC - basic uclass type for PMIC I/O, which provides common
22 - UCLASS_REGULATOR - additional uclass type for specific PMIC features,
23 which are Voltage/Current regulators.
27 - drivers/power/pmic/pmic-uclass.c
28 - include/power/pmic.h
30 - drivers/power/regulator/regulator-uclass.c
31 - include/power/regulator.h
35 - common/cmd_regulator.c
39 The Power Management Integrated Circuits (PMIC) are used in embedded systems
40 to provide stable, precise and specific voltage power source with over-voltage
41 and thermal protection circuits.
43 The single PMIC can provide various functions by single or multiple interfaces,
44 like in the example below.
48 | ______________________________________
49 | BUS 0 | Multi interface PMIC IC |--> LDO out 1
50 | e.g.I2C0 | |--> LDO out N
51 |-----------|---- PMIC device 0 (READ/WRITE ops) |
52 | or SPI0 | |_ REGULATOR device (ldo/... ops) |--> BUCK out 1
53 | | |_ CHARGER device (charger ops) |--> BUCK out M
54 | | |_ MUIC device (microUSB con ops) |
55 | BUS 1 | |_ ... |---> BATTERY
57 |-----------|---- PMIC device 1 (READ/WRITE ops) |---> USB in 1
58 . or SPI1 | |_ RTC device (rtc ops) |---> USB in 2
59 . |______________________________________|---> USB out
62 Since U-Boot provides driver model features for I2C and SPI bus drivers,
63 the PMIC devices should also support this. By the pmic and regulator API's,
64 PMIC drivers can simply provide a common functions, for multi-interface and
65 and multi-instance device support.
67 Basic design assumptions:
69 - Common I/O API - UCLASS_PMIC
70 For the multi-function PMIC devices, this can be used as parent I/O device
71 for each IC's interface. Then, each children uses the same dev for read/write.
73 - Common regulator API - UCLASS_REGULATOR
74 For driving the regulator attributes, auto setting function or command line
75 interface, based on kernel-style regulator device tree constraints.
77 For simple implementations, regulator drivers are not required, so the code can
78 use pmic read/write directly.
82 The basic informations:
83 * Uclass: 'UCLASS_PMIC'
84 * Header: 'include/power/pmic.h'
85 * Core: 'drivers/power/pmic/pmic-uclass.c'
86 config: 'CONFIG_DM_PMIC'
87 * Command: 'common/cmd_pmic.c'
88 config: 'CONFIG_CMD_PMIC'
89 * Example: 'drivers/power/pmic/max77686.c'
91 This is still under the construction. So for the API description, please refer
94 As an example of the pmic driver, please refer to the MAX77686 driver.
96 Please pay attention for the driver's '.bind' method. Exactly the function call:
97 'pmic_bind_childs()', which is used to bind the regulators by using the array of
98 regulator's node, compatible prefixes.
100 The 'pmic; command also supports the new API. So the pmic command can be enabled
101 by adding CONFIG_CMD_PMIC.
102 The new pmic command allows to:
104 - choose the current device (like the mmc command)
105 - read or write the pmic register
106 - dump all pmic registers
108 This command can use only UCLASS_PMIC devices, since this uclass is designed
109 for pmic I/O operations only.
111 For more informations, please refer to the file: 'common/cmd_pmic.c'.
115 The basic informations:
116 * Uclass: 'UCLASS_REGULATOR'
117 * Header: 'include/power/regulator.h'
118 * Core: 'drivers/power/regulator/regulator-uclass.c'
119 config: 'CONFIG_DM_REGULATOR'
120 binding: 'doc/device-tree-bindings/regulator/regulator.txt'
121 * Command: 'common/cmd_regulator.c'
122 config: 'CONFIG_CMD_REGULATOR'
123 * Example: 'drivers/power/regulator/max77686.c'
124 'drivers/power/pmic/max77686.c' (required I/O driver for the above)
125 * Example: 'drivers/power/regulator/fixed.c'
126 config" 'CONFIG_DM_REGULATOR_FIXED'
128 This is still under the construction. So for the API description, please refer
131 For the example regulator driver, please refer to the MAX77686 regulator driver,
132 but this driver can't operate without pmic's example driver, which provides an
133 I/O interface for MAX77686 regulator.
135 The second example is a fixed Voltage/Current regulator for a common use.
137 The 'regulator' command also supports the new API. The command allow:
138 - list regulator devices
139 - choose the current device (like the mmc command)
140 - do all regulator-specific operations
142 For more informations, please refer to the file: 'common/cmd_regulator.c'