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

[Przemyslaw Marczak <p.marczak@samsung.com>]

Hello Simon,

On 03/29/2015 03:08 PM, Simon Glass wrote:
> Hi Przemyslaw,
>
> On 24 March 2015 at 14:30, Przemyslaw Marczak <p.marczak@samsung.com> wrote:
>> Signed-off-by: Przemyslaw Marczak <p.marczak@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@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?
>

Right, this was unclear.
I meant the hardware connected by I/O expansion header, which can be 
replaced by other. And each could be supplied by a different voltage value.

>> --
>> 1.9.1
>>
>
> Regards,
> Simon
>

I didn't clean this file too much, last time. Will fix in next version.
Thanks for help!
-- 
Przemyslaw Marczak
Samsung R&D Institute Poland
Samsung Electronics
p.marczak at samsung.com