[U-Boot] [PATCH v3 13/17] doc: driver-model: pmic and regulator uclass documentation

[Simon Glass]

Hi Przemyslaw,

On 24 March 2015 at 14:30, Przemyslaw Marczak <p.marczak at samsung.com> wrote:
> Signed-off-by: Przemyslaw Marczak <p.marczak at samsung.com>
> ---
> Changes v2, V3:
> - update documentation with the framework api changes
> - remove doc file name 'dm' prefix
> ---
>  doc/driver-model/pmic-framework.txt | 350 ++++++++++++++++++++++++++++++++++++
>  1 file changed, 350 insertions(+)
>  create mode 100644 doc/driver-model/pmic-framework.txt
>
> diff --git a/doc/driver-model/pmic-framework.txt b/doc/driver-model/pmic-framework.txt
> new file mode 100644
> index 0000000..72651dc
> --- /dev/null
> +++ b/doc/driver-model/pmic-framework.txt
> @@ -0,0 +1,350 @@
> +#
> +# (C) Copyright 2014-2015 Samsung Electronics
> +# Przemyslaw Marczak <p.marczak at samsung.com>
> +#
> +# SPDX-License-Identifier:      GPL-2.0+
> +#
> +
> +PMIC framework based on Driver Model
> +====================================
> +TOC:
> +1. Introduction
> +2. How does it work
> +3. Pmic driver api
> +4. Pmic driver
> +5. Pmic command
> +6. Regulator driver api
> +7. Regulator driver
> +8. Regulator command
> +
> +1. Introduction
> +===============
> +This is an introduction to driver-model multi uclass PMIC devices support.
> +At present it is 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 various voltage regulators.
> +
> +New files:
> +UCLASS_PMIC:
> +- drivers/power/pmic-uclass.c
> +- include/power/pmic.h
> +UCLASS_REGULATOR:
> +- drivers/power/regulator-uclass.c
> +- include/power/regulator.h
> +
> +Commands:
> +- lib/cmd_pmic.c
> +- lib/cmd_regulator.c
> +
> +2. 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 functionalities with 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. With the new basic uclass types
> +for PMIC I/O and regulator features, PMIC drivers can simply provide common
> +features, with multiple interface and instance support.
> +
> +Basic design assumptions:
> +
> +- Common I/O api - UCLASS_PMIC
> +The main assumption is to use UCLASS_PMIC device to provide I/O interface,

an I/O interface

> +for devices other uclass types. It is no matter what is the type of device
> +physical I/O interface.

devices of other uclass types. It doesn't matter what type of physical
I/O interface is used.


Usually PMIC devices are using SPI or I2C interface,

s/are using/use/

> +but use of any other interface (e.g. when PMIC is not directly connected
> +to the SoC) - is now possible. Drivers can use the same read/write api.
> +
> +- Common regulator api - UCLASS_REGULATOR
> +For setting the attributes of verious types of regulators with common api,

various

with a common

> +this uclass can be implemented. This allows to drive the each regulator output

allows driving each regulator's output

> +value, on/off state and custom defined operation modes. It also provides the

custom-defined

or perhaps just 'particular'

> +user interface for all operations.
> +For the very simple implementation, the regulator drivers are not required,

For simple implementations, regulator drivers are not required, so the
code can use pmic read/write directly.

> +so the code could base on pmic read/write only.
> +
> +When board device-tree file includes pmic subnode and the U_Boot compatible
> +driver exists, then the pmic device bind should looks like this:
> +
> +|_ root - will bind the device for I2C/SPI bus node
> +  |_ i2c/spi - should bind a device for pmic node
> +    |_ pmic (parent) - should bind child devices for its features
> +      |_ regulator (child)
> +      |_ charger   (child)
> +      |_ other     (child)
> +
> +Usually PMIC design provides:
> + - single I/O interface (single UCLASS_PMIC driver)
> +   Then UCLASS_PMIC device should be a parent of all pmic devices, where each
> +   is usually different uclass type, but need to access the same interface
> +
> + - multiple I/O interfaces (UCLASS_PMIC driver for each)
> +   For each interface the UCLASS_PMIC device should be a parent of only those
> +   devices (different uclass types), which needs to access the specified
> +   interface.
> +
> +3. Pmic driver api
> +===================
> +To use the pmic API, config: CONFIG_DM_PMIC is required.
> +The new driver API is very simple and is based on 'struct dm_pmic_ops',
> +which define two basic operations: device read and write.
> +
> +The platform data is introduced as 'struct pmic_platdata', to keep an info
> +about the device interface.
> +
> +The api is described in file: 'include/power/pmic.h'
> +Getting the device:
> +- by name  -  int pmic_get(char *name, struct udevice **pmic);
> +
> +Device I/O interface
> +Can be used with UCLASS_PMIC devices:
> +- Read from the device 'len' bytes at 'reg' into the buffer:
> +  int pmic_read(struct udevice *dev, uint reg, uint8_t *buffer, int len);
> +
> +- Write to the device 'len' bytes at 'reg' from the buffer:
> +  int pmic_write(struct udevice *dev, uint reg, uint8_t *buffer, int len);
> +
> +4. Pmic driver
> +============================
> +As an example of the pmic driver, please take a look into the MAX77686 driver
> +'drivers/power/pmic/max77686.c' and the description in 'include/power/pmic.h'
> +
> +The pmic driver can be defined by U_BOOT_DRIVER() macro:
> +
> +U_BOOT_DRIVER(pmic_max77686) = {
> +       .name = "max77686 pmic",
> +       .id = UCLASS_PMIC,
> +       .of_match = max77686_ids,     - Allows to bind by compatible
> +       .bind = max77686_bind,        - Function called at device bind
> +       .ops = &max77686_ops,         - Pmic api function calls
> +       .platdata_auto_alloc_size = sizeof(struct pmic_platdata),
> +};
> +
> +To bind the pmic device, field '.of_match' is required with proper compatible.
> +
> +Driver ops:
> +.reg_count = MAX77686_NUM_OF_REGS - number of pmic registers
> +.read = max77686_read() - allows to use pmic_read()
> +.write = max77686_write() - allows to use pmic_write()
> +
> +Driver bind:
> +- max77686_bind(): called on bind and calls pmic_child_node_scan() to bind the
> +  childs which are int "voltage-regulators" subnode. The bind is done using
> +  "voltage-regulators" property name.
> +
> +5. Pmic command
> +===============
> +To use the pmic command, config: CONFIG_DM_PMIC_CMD is required.
> +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.
> +
> +Command options (pmic [option]):
> +- list                     - list available PMICs
> +- dev <id>                 - set id to current pmic device
> +- pmic dump                - dump registers
> +- pmic read <reg>          - read register
> +- pmic write <reg> <value> - write register
> +
> +Example of usage:
> +# pmic list           - chose one dev Id, e.g. 3
> +# pmic dev 0          - set dev seq 0 as current device
> +# pmic dump           - dump the registers of the current pmic dev
> +# pmic read 0x0       - read the register at address 0x0
> +# pmic write 0x0 0x1  - write 0x1 to the register at addres 0x0
> +
> +6. Regulator driver API
> +===================================
> +To use the regulator API, config: CONFIG_DM_REGULATOR is required.
> +The api is described in file: 'include/power/regulator.h'
> +The api is based on structure types:
> +- 'dm_regulator_info' - dev->uc_priv (auto-allocated)
> +- 'dm_regulator_mode' - included in regualtor info
> +
> +Regulator info keeps the constraints taken from the device-tree and also device
> +modes set by the driver (single or array).
> +
> +The fixed-regulator common driver keeps provides private structure type, to keep
> +its gpio attributes. The structure type 'fixed_regulator_priv' is keept in field

kept

> +'dev->priv' and is allocated by the driver.
> +
> +6.1 Regulator device-tree node:
> +The regulator node should looks like in the example:
> +ldo1 {
> +        regulator-compatible = "LDO1"; (not used here, but required for bind)
> +        regulator-name = "VDD_MMC_1.8V"; (mandatory) *
> +        regulator-min-microvolt = <1000000>; (mandatory) *
> +        regulator-max-microvolt = <1000000>; (mandatory) *
> +        regulator-min-microamp = <1000>; (optional) *
> +        regulator-max-microamp = <1000>; (optional) *
> +        regulator-always-on; (optional) *
> +        regulator-boot-on; (optional) *
> +};
> +
> +For the fixed-voltage regulator, voltage min and max must be equal:
> +VDD_MMC: regulator at 0 {
> +        compatible = "regulator-fixed";
> +        regulator-name = "VDD_MMC"; (mandatory) *
> +        regulator-min-microvolt = <2800000>; (mandatory) *
> +        regulator-max-microvolt = <2800000>; (mandatory) *
> +        regulator-always-on; (optional)
> +        regulator-boot-on; (optional)
> +        gpio = <&gpc 1 GPIO_ACTIVE_HIGH>; (optional)
> +        gpio-open-drain; (optional)
> +        enable-active-high; (optional)
> +        startup-delay-us
> +};
> +
> +The attributes signed with '*' can be taken by the common function which is
> +regulator_ofdata_to_platdata(). The rest attributes for fixed-regulator, are
> +taken by the driver.
> +
> +6.2 Getting the device:
> +- by name - int regulator_get(char *name, struct udevice **regulator);
> +
> +6.3 Device I/O interface
> +According to the framework assumptions, where uclass pmic device is a parent
> +of pmic devices other uclass types, the regulator devices should use uclass
> +pmic interface, with the parent as the device, like this:
> +- pmic_read(regulator->parent, some_reg, &some_buff, count);
> +- pmic_write(regulator->parent, some_reg, &some_buff, count);
> +
> +6.4 Device regulator operations
> +The regulator function calls are based on few data types:
> +- enum regulator_type {...} - standard types: LDO, BUCK, DVS, FIXED
> +- struct dm_regulator_info {...} - output name and value limits
> +- struct dm_regulator_mode {...} - output operation mode value and name
> +- struct dm_regulator_ops {...} - regulator driver function calls
> +
> +The first argument is always device. And the device uclass id must be always:
> +- 'UCLASS_REGULATOR'
> +
> +Function details are described in regulator header. The basic features are:
> +- regulator_info()            - get the regulator info structure
> +- regulator_mode()            - get the regulator mode info structure
> +- regulator_get/set_value()   - get/set the regulator output voltage
> +- regulator_get/set_current() - get/set the regulator output current
> +- regulator_get/set_enable()  - get/set the regulator output enable state
> +- regulator_get/set_mode()    - get/set the regulator output operation mode
> +
> +7. Regulator driver
> +======================================
> +As an example of the regulator driver, please take a look into the MAX77686
> +regulator driver (drivers/power/regulator/max77686.c). It implements two drivers
> +for the buck and ldo regulators. The buck driver structure:
> +
> +U_BOOT_DRIVER(max77686_buck) = {
> +        .name = "max77686 buck",
> +        .id = UCLASS_REGULATOR,
> +        .ops = &max77686_buck_ops,
> +        .of_match = max77686_buck_ids,
> +        .ofdata_to_platdata = max77686_buck_ofdata_to_platdata,
> +};
> +
> +The device-tree buck compatibles:
> +static const struct udevice_id max77686_buck_ids[] = {
> +        { .compatible = "BUCK1", .data = 1 },
> +        { .compatible = "BUCK2", .data = 2 },
> +        ...
> +        { }, (need always put null at the end)
> +};
> +
> +For each compatible, the data is set as a number of buck. This allows to get
> +the device number without parsing the compatible.
> +
> +The buck driver '.ofdata_to_platdata' call implementation:
> +static int max77686_buck_ofdata_to_platdata(struct udevice *dev)
> +{
> +        struct dm_regulator_info *info = dev->uclass_priv;
> +        int ret;
> +
> +       /* Get the regulation constraints by the common function */
> +        ret = regulator_ofdata_to_platdata(dev);
> +        if (ret)
> +                return ret;
> +
> +        info->type = REGULATOR_TYPE_BUCK;
> +        /**
> +         * The device mode array is filled by internal driver function with
> +         * the proper name for each mode id.
> +         */
> +        info->mode_count = max77686_buck_modes(dev2num(dev), &info->mode);
> +
> +        return 0;
> +}
> +
> +And the call to regulator_ofdata_to_platdata() is responsible for filling the
> +regulator output constraints, which are keepts in device-tree regulator nodes,
> +e.g. 'arch/arm/dts/exynos4412-odroid.dts'
> +
> +For the I/O, this driver uses pmic_read/write calls, with the parent device
> +as the first argument, e.g.: pmic_read(dev->parent, adr, &val, 1);
> +
> +8. Regulator command
> +====================
> +To use the pmic command, config: CONFIG_DM_REGULATOR_CMD is required.
> +
> +This command is based on driver model regulator api.
> +User interface features:
> +- list                   - list UCLASS regulator devices
> +- regulator dev [id]     - show or [set] operating regulator device
> +- regulator [info]       - print constraints info
> +- regulator [status]     - print operating status
> +- regulator [value] [-f] - print/[set] voltage value [uV] (force)
> +- regulator [current]    - print/[set] current value [uA]
> +- regulator [mode_id]    - print/[set] operating mode id
> +- regulator [enable]     - enable the regulator output
> +- regulator [disable]    - disable the regulator output
> +
> +If pmic device driver provides support to this another pmic uclass, then this
> +command provides useful user interface. It was designed to allow safe I/O access
> +to the pmic device, without the pmic documentation. If driver provide regulator
> +output - value and mode info - then user can operate on it.
> +
> +Example of usage:
> +regulator list              - look after regulator 'seq' number
> +regulator dev 'seq'         - set current device
> +regulator status            - show device status
> +regulator info              - list device available regulation constraints
> +regulator value             - prints device voltage value
> +regulator value 1000000     - set device voltage value to 1000000 uV
> +regulator value 1200000 -f  - if value exceeds limits - set force
> +regulator mode              - print device operation mode id
> +regulator mode 5            - set devices operation mode to '5' (mode id)
> +
> +The -f option (forcibly) or mode - only if descriptor is available

I think something like this would be clearer:

The -f option (forcibly) and 'mode' sub-command are only available if
the regulator descriptor is available


> +
> +Note:
> +The regulator descriptor, 'min' and 'max' limits prevents setting unsafe value.
> +But sometimes it is useful to change the regulator value for some test - so the
> +force option (-f) is available. This option is not available for change the mode
> +since this depends on a pmic device design, but the required voltage value can
> +change, e.g. if some hardware uses pins header.

changed.

What does "e..g. if some hardware uses pins header" mean? Can you
reword that to be clearer?

> --
> 1.9.1
>

Regards,
Simon