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- .. SPDX-License-Identifier: GPL-2.0+
- .. (C) Copyright 2014-2015 Samsung Electronics
- .. sectionauthor:: Przemyslaw Marczak <p.marczak@samsung.com>
- PMIC framework based on Driver Model
- ====================================
- Introduction
- ------------
- This is an introduction to driver-model multi uclass PMIC IC's support.
- At present it's based on two uclass types:
- UCLASS_PMIC:
- basic uclass type for PMIC I/O, which provides common
- read/write interface.
- UCLASS_REGULATOR:
- additional uclass type for specific PMIC features, which are
- Voltage/Current regulators.
- New files:
- UCLASS_PMIC:
- - drivers/power/pmic/pmic-uclass.c
- - include/power/pmic.h
- UCLASS_REGULATOR:
- - drivers/power/regulator/regulator-uclass.c
- - include/power/regulator.h
- Commands:
- - common/cmd_pmic.c
- - common/cmd_regulator.c
- How doees it work
- -----------------
- The Power Management Integrated Circuits (PMIC) are used in embedded systems
- to provide stable, precise and specific voltage power source with over-voltage
- and thermal protection circuits.
- The single PMIC can provide various functions by single or multiple interfaces,
- like in the example below::
- -- SoC
- |
- | ______________________________________
- | BUS 0 | Multi interface PMIC IC |--> LDO out 1
- | e.g.I2C0 | |--> LDO out N
- |-----------|---- PMIC device 0 (READ/WRITE ops) |
- | or SPI0 | |_ REGULATOR device (ldo/... ops) |--> BUCK out 1
- | | |_ CHARGER device (charger ops) |--> BUCK out M
- | | |_ MUIC device (microUSB con ops) |
- | BUS 1 | |_ ... |---> BATTERY
- | e.g.I2C1 | |
- |-----------|---- PMIC device 1 (READ/WRITE ops) |---> USB in 1
- . or SPI1 | |_ RTC device (rtc ops) |---> USB in 2
- . |______________________________________|---> USB out
- .
- Since U-Boot provides driver model features for I2C and SPI bus drivers,
- the PMIC devices should also support this. By the pmic and regulator API's,
- PMIC drivers can simply provide a common functions, for multi-interface and
- and multi-instance device support.
- Basic design assumptions:
- - Common I/O API:
- UCLASS_PMIC. For the multi-function PMIC devices, this can be used as
- parent I/O device for each IC's interface. Then, each children uses the
- same dev for read/write.
- - Common regulator API:
- UCLASS_REGULATOR. For driving the regulator attributes, auto setting
- function or command line interface, based on kernel-style regulator device
- tree constraints.
- For simple implementations, regulator drivers are not required, so the code can
- use pmic read/write directly.
- Pmic uclass
- -----------
- The basic information:
- * Uclass: 'UCLASS_PMIC'
- * Header: 'include/power/pmic.h'
- * Core: 'drivers/power/pmic/pmic-uclass.c' (config 'CONFIG_DM_PMIC')
- * Command: 'common/cmd_pmic.c' (config 'CONFIG_CMD_PMIC')
- * Example: 'drivers/power/pmic/max77686.c'
- For detailed API description, please refer to the header file.
- As an example of the pmic driver, please refer to the MAX77686 driver.
- Please pay attention for the driver's bind() method. Exactly the function call:
- 'pmic_bind_children()', which is used to bind the regulators by using the array
- of regulator's node, compatible prefixes.
- The 'pmic; command also supports the new API. So the pmic command can be enabled
- by adding CONFIG_CMD_PMIC.
- The new pmic command allows to:
- - list pmic devices
- - choose the current device (like the mmc command)
- - read or write the pmic register
- - dump all pmic registers
- This command can use only UCLASS_PMIC devices, since this uclass is designed
- for pmic I/O operations only.
- For more information, please refer to the core file.
- Regulator uclass
- ----------------
- The basic information:
- * Uclass: 'UCLASS_REGULATOR'
- * Header: 'include/power/regulator.h'
- * Core: 'drivers/power/regulator/regulator-uclass.c'
- (config 'CONFIG_DM_REGULATOR')
- * Binding: 'doc/device-tree-bindings/regulator/regulator.txt'
- * Command: 'common/cmd_regulator.c' (config 'CONFIG_CMD_REGULATOR')
- * Example: 'drivers/power/regulator/max77686.c'
- 'drivers/power/pmic/max77686.c' (required I/O driver for the above)
- * Example: 'drivers/power/regulator/fixed.c'
- (config 'CONFIG_DM_REGULATOR_FIXED')
- For detailed API description, please refer to the header file.
- For the example regulator driver, please refer to the MAX77686 regulator driver,
- but this driver can't operate without pmic's example driver, which provides an
- I/O interface for MAX77686 regulator.
- The second example is a fixed Voltage/Current regulator for a common use.
- The 'regulator' command also supports the new API. The command allow:
- - list regulator devices
- - choose the current device (like the mmc command)
- - do all regulator-specific operations
- For more information, please refer to the command file.
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