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