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dm: adc: add simple ADC uclass implementation

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This commit adds:
- new uclass id: UCLASS_ADC
- new uclass driver: drivers/adc/adc-uclass.c

The new uclass's API allows for ADC operation on:
* single-channel with channel selection by a number
* multti-channel with channel selection by bit mask

ADC uclass's functions:
* single-channel:
  - adc_start_channel()        - start channel conversion
  - adc_channel_data()         - get conversion data
  - adc_channel_single_shot()  - start/get conversion data
* multi-channel:
  - adc_start_channels()       - start selected channels conversion
  - adc_channels_data()        - get conversion data
  - adc_channels_single_shot() - start/get conversion data for channels
                                 selected by bit mask
* general:
  - adc_stop()      - stop the conversion
  - adc_vdd_value() - positive reference Voltage value with polarity [uV]
  - adc_vss_value() - negative reference Voltage value with polarity [uV]
  - adc_data_mask() - conversion data bit mask

The device tree can provide below constraints/properties:
- vdd-polarity-negative: if true: Vdd = vdd-microvolts * (-1)
- vss-polarity-negative: if true: Vss = vss-microvolts * (-1)
- vdd-supply:            phandle to Vdd regulator's node
- vss-supply:            phandle to Vss regulator's node
And optional, checked only if the above corresponding, doesn't exist:
  - vdd-microvolts:      positive reference Voltage [uV]
  - vss-microvolts:      negative reference Voltage [uV]

Signed-off-by: Przemyslaw Marczak <p.marczak@samsung.com>
Cc: Simon Glass <sjg@chromium.org>
Signed-off-by: Minkyu Kang <mk7.kang@samsung.com>
This commit is contained in:
Przemyslaw Marczak 2015-10-27 13:08:00 +01:00 committed by Minkyu Kang
parent 7c816e24a4
commit 5decbf5300
8 changed files with 783 additions and 0 deletions
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62
doc/device-tree-bindings/adc/adc.txt Normal file
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ADC device binding
There are no mandatory properties for ADC. However, if Voltage info is required,
then there are two options:
- use microvolts constraint or
- use regulator phandle to enable/read supply's Voltage
Properties and constraints:
*optional and always checked, Voltage polarity info:
- vdd-polarity-negative: positive reference Voltage has a negative polarity
- vss-polarity-negative: negative reference Voltage has a negative polarity
Chose one option, for each supply (Vdd/Vss):
*optional and always checked, supply Voltage constants:
- vdd-supply: phandle to Vdd regulator's node
- vss-supply: phandle to Vss regulator's node
*optional and checked only if the above corresponding, doesn't exist:
- vdd-microvolts: positive reference Voltage value [uV]
- vss-microvolts: negative reference Voltage value [uV]
Example with constant 'Vdd' value:
adc@1000000 {
compatible = "some-adc";
reg = <0xaabb000 0x100>;
status = "enabled";
vdd-microvolts = <1800000>;
};
Example of supply phandle usage, for the ADC's VDD/VSS references as below:
_______ _______
|Sandbox| |Sandbox|
: PMIC : : ADC :
. . . .
| | (Vdd) | AIN0|-->
| BUCK2|-------|VDDref |
| (3.3V)| _|VSSref |
|_______| | |_______|
_|_
For the above PMIC, the node can be defined as follows:
sandbox_pmic {
compatible = "sandbox,pmic";
...
buck2: buck2 {
regulator-name = "SUPPLY_3.3V";
regulator-min-microvolt = <3300000>;
regulator-max-microvolt = <3300000>;
};
...
};
For the above ADC, the node can be defined as follows:
adc@0 {
compatible = "sandbox,adc";
vdd-supply = <&buck2>;
vss-microvolts = <0>;
};
The ADC uclass code, will enable the supply before start of the conversion,
but it will not configure the regulator settings.

2
drivers/Kconfig
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@ -4,6 +4,8 @@ source "drivers/core/Kconfig"
# types of drivers sorted in alphabetical order
source "drivers/adc/Kconfig"
source "drivers/block/Kconfig"
source "drivers/clk/Kconfig"

1
drivers/Makefile
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@ -35,6 +35,7 @@ obj-$(CONFIG_SPL_SATA_SUPPORT) += block/
else
obj-y += adc/
obj-$(CONFIG_DM_DEMO) += demo/
obj-$(CONFIG_BIOSEMU) += bios_emulator/
obj-y += block/

12
drivers/adc/Kconfig Normal file
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config ADC
bool "Enable ADC drivers using Driver Model"
help
This enables ADC API for drivers, which allows driving ADC features
by single and multi-channel methods for:
- start/stop/get data for conversion of a single-channel selected by
a number or multi-channels selected by a bitmask
- get data mask (ADC resolution)
ADC reference Voltage supply options:
- methods for get Vdd/Vss reference Voltage values with polarity
- support supply's phandle with auto-enable
- supply polarity setting in fdt

8
drivers/adc/Makefile Normal file
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#
# Copyright (C) 2015 Samsung Electronics
# Przemyslaw Marczak <p.marczak@samsung.com>
#
# SPDX-License-Identifier: GPL-2.0+
#
obj-$(CONFIG_ADC) += adc-uclass.o

409
drivers/adc/adc-uclass.c Normal file
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/*
* Copyright (C) 2015 Samsung Electronics
* Przemyslaw Marczak <p.marczak@samsung.com>
*
* SPDX-License-Identifier: GPL-2.0+
*/
#include <common.h>
#include <errno.h>
#include <dm.h>
#include <dm/lists.h>
#include <dm/device-internal.h>
#include <dm/uclass-internal.h>
#include <adc.h>
#include <power/regulator.h>
DECLARE_GLOBAL_DATA_PTR;
#define ADC_UCLASS_PLATDATA_SIZE sizeof(struct adc_uclass_platdata)
#define CHECK_NUMBER true
#define CHECK_MASK (!CHECK_NUMBER)
/* TODO: add support for timer uclass (for early calls) */
#ifdef CONFIG_SANDBOX_ARCH
#define sdelay(x) udelay(x)
#else
extern void sdelay(unsigned long loops);
#endif
static int check_channel(struct udevice *dev, int value, bool number_or_mask,
const char *caller_function)
{
struct adc_uclass_platdata *uc_pdata = dev_get_uclass_platdata(dev);
unsigned mask = number_or_mask ? (1 << value) : value;
/* For the real ADC hardware, some ADC channels can be inactive.
* For example if device has 4 analog channels, and only channels
* 1-st and 3-rd are valid, then channel mask is: 0b1010, so request
* with mask 0b1110 should return an error.
*/
if ((uc_pdata->channel_mask >= mask) && (uc_pdata->channel_mask & mask))
return 0;
printf("Error in %s/%s().\nWrong channel selection for device: %s\n",
__FILE__, caller_function, dev->name);
return -EINVAL;
}
static int adc_supply_enable(struct udevice *dev)
{
struct adc_uclass_platdata *uc_pdata = dev_get_uclass_platdata(dev);
const char *supply_type;
int ret = 0;
if (uc_pdata->vdd_supply) {
supply_type = "vdd";
ret = regulator_set_enable(uc_pdata->vdd_supply, true);
}
if (!ret && uc_pdata->vss_supply) {
supply_type = "vss";
ret = regulator_set_enable(uc_pdata->vss_supply, true);
}
if (ret)
error("%s: can't enable %s-supply!", dev->name, supply_type);
return ret;
}
int adc_data_mask(struct udevice *dev, unsigned int *data_mask)
{
struct adc_uclass_platdata *uc_pdata = dev_get_uclass_platdata(dev);
if (!uc_pdata)
return -ENOSYS;
*data_mask = uc_pdata->data_mask;
return 0;
}
int adc_stop(struct udevice *dev)
{
const struct adc_ops *ops = dev_get_driver_ops(dev);
if (!ops->stop)
return -ENOSYS;
return ops->stop(dev);
}
int adc_start_channel(struct udevice *dev, int channel)
{
const struct adc_ops *ops = dev_get_driver_ops(dev);
int ret;
if (!ops->start_channel)
return -ENOSYS;
ret = check_channel(dev, channel, CHECK_NUMBER, __func__);
if (ret)
return ret;
ret = adc_supply_enable(dev);
if (ret)
return ret;
return ops->start_channel(dev, channel);
}
int adc_start_channels(struct udevice *dev, unsigned int channel_mask)
{
const struct adc_ops *ops = dev_get_driver_ops(dev);
int ret;
if (!ops->start_channels)
return -ENOSYS;
ret = check_channel(dev, channel_mask, CHECK_MASK, __func__);
if (ret)
return ret;
ret = adc_supply_enable(dev);
if (ret)
return ret;
return ops->start_channels(dev, channel_mask);
}
int adc_channel_data(struct udevice *dev, int channel, unsigned int *data)
{
struct adc_uclass_platdata *uc_pdata = dev_get_uclass_platdata(dev);
const struct adc_ops *ops = dev_get_driver_ops(dev);
unsigned int timeout_us = uc_pdata->data_timeout_us;
int ret;
if (!ops->channel_data)
return -ENOSYS;
ret = check_channel(dev, channel, CHECK_NUMBER, __func__);
if (ret)
return ret;
do {
ret = ops->channel_data(dev, channel, data);
if (!ret || ret != -EBUSY)
break;
/* TODO: use timer uclass (for early calls). */
sdelay(5);
} while (timeout_us--);
return ret;
}
int adc_channels_data(struct udevice *dev, unsigned int channel_mask,
struct adc_channel *channels)
{
struct adc_uclass_platdata *uc_pdata = dev_get_uclass_platdata(dev);
unsigned int timeout_us = uc_pdata->multidata_timeout_us;
const struct adc_ops *ops = dev_get_driver_ops(dev);
int ret;
if (!ops->channels_data)
return -ENOSYS;
ret = check_channel(dev, channel_mask, CHECK_MASK, __func__);
if (ret)
return ret;
do {
ret = ops->channels_data(dev, channel_mask, channels);
if (!ret || ret != -EBUSY)
break;
/* TODO: use timer uclass (for early calls). */
sdelay(5);
} while (timeout_us--);
return ret;
}
int adc_channel_single_shot(const char *name, int channel, unsigned int *data)
{
struct udevice *dev;
int ret;
ret = uclass_get_device_by_name(UCLASS_ADC, name, &dev);
if (ret)
return ret;
ret = adc_start_channel(dev, channel);
if (ret)
return ret;
ret = adc_channel_data(dev, channel, data);
if (ret)
return ret;
return 0;
}
static int _adc_channels_single_shot(struct udevice *dev,
unsigned int channel_mask,
struct adc_channel *channels)
{
unsigned int data;
int channel, ret;
for (channel = 0; channel <= ADC_MAX_CHANNEL; channel++) {
/* Check channel bit. */
if (!((channel_mask >> channel) & 0x1))
continue;
ret = adc_start_channel(dev, channel);
if (ret)
return ret;
ret = adc_channel_data(dev, channel, &data);
if (ret)
return ret;
channels->id = channel;
channels->data = data;
channels++;
}
return 0;
}
int adc_channels_single_shot(const char *name, unsigned int channel_mask,
struct adc_channel *channels)
{
struct udevice *dev;
int ret;
ret = uclass_get_device_by_name(UCLASS_ADC, name, &dev);
if (ret)
return ret;
ret = adc_start_channels(dev, channel_mask);
if (ret)
goto try_manual;
ret = adc_channels_data(dev, channel_mask, channels);
if (ret)
return ret;
return 0;
try_manual:
if (ret != -ENOSYS)
return ret;
return _adc_channels_single_shot(dev, channel_mask, channels);
}
static int adc_vdd_platdata_update(struct udevice *dev)
{
struct adc_uclass_platdata *uc_pdata = dev_get_uclass_platdata(dev);
int ret;
/* Warning!
* This function can't return supply device before its bind.
* Please pay attention to proper fdt scan sequence. If ADC device
* will bind before its supply regulator device, then the below 'get'
* will return an error.
*/
ret = device_get_supply_regulator(dev, "vdd-supply",
&uc_pdata->vdd_supply);
if (ret)
return ret;
ret = regulator_get_value(uc_pdata->vdd_supply);
if (ret < 0)
return ret;
uc_pdata->vdd_microvolts = ret;
return 0;
}
static int adc_vss_platdata_update(struct udevice *dev)
{
struct adc_uclass_platdata *uc_pdata = dev_get_uclass_platdata(dev);
int ret;
ret = device_get_supply_regulator(dev, "vss-supply",
&uc_pdata->vss_supply);
if (ret)
return ret;
ret = regulator_get_value(uc_pdata->vss_supply);
if (ret < 0)
return ret;
uc_pdata->vss_microvolts = ret;
return 0;
}
int adc_vdd_value(struct udevice *dev, int *uV)
{
struct adc_uclass_platdata *uc_pdata = dev_get_uclass_platdata(dev);
int ret, value_sign = uc_pdata->vdd_polarity_negative ? -1 : 1;
if (!uc_pdata->vdd_supply)
goto nodev;
/* Update the regulator Value. */
ret = adc_vdd_platdata_update(dev);
if (ret)
return ret;
nodev:
if (uc_pdata->vdd_microvolts == -ENODATA)
return -ENODATA;
*uV = uc_pdata->vdd_microvolts * value_sign;
return 0;
}
int adc_vss_value(struct udevice *dev, int *uV)
{
struct adc_uclass_platdata *uc_pdata = dev_get_uclass_platdata(dev);
int ret, value_sign = uc_pdata->vss_polarity_negative ? -1 : 1;
if (!uc_pdata->vss_supply)
goto nodev;
/* Update the regulator Value. */
ret = adc_vss_platdata_update(dev);
if (ret)
return ret;
nodev:
if (uc_pdata->vss_microvolts == -ENODATA)
return -ENODATA;
*uV = uc_pdata->vss_microvolts * value_sign;
return 0;
}
static int adc_vdd_platdata_set(struct udevice *dev)
{
struct adc_uclass_platdata *uc_pdata = dev_get_uclass_platdata(dev);
int ret, offset = dev->of_offset;
const void *fdt = gd->fdt_blob;
char *prop;
prop = "vdd-polarity-negative";
uc_pdata->vdd_polarity_negative = fdtdec_get_bool(fdt, offset, prop);
ret = adc_vdd_platdata_update(dev);
if (ret != -ENOENT)
return ret;
/* No vdd-supply phandle. */
prop = "vdd-microvolts";
uc_pdata->vdd_microvolts = fdtdec_get_int(fdt, offset, prop, -ENODATA);
return 0;
}
static int adc_vss_platdata_set(struct udevice *dev)
{
struct adc_uclass_platdata *uc_pdata = dev_get_uclass_platdata(dev);
int ret, offset = dev->of_offset;
const void *fdt = gd->fdt_blob;
char *prop;
prop = "vss-polarity-negative";
uc_pdata->vss_polarity_negative = fdtdec_get_bool(fdt, offset, prop);
ret = adc_vss_platdata_update(dev);
if (ret != -ENOENT)
return ret;
/* No vss-supply phandle. */
prop = "vss-microvolts";
uc_pdata->vss_microvolts = fdtdec_get_int(fdt, offset, prop, -ENODATA);
return 0;
}
static int adc_pre_probe(struct udevice *dev)
{
int ret;
/* Set ADC VDD platdata: polarity, uV, regulator (phandle). */
ret = adc_vdd_platdata_set(dev);
if (ret)
error("%s: Can't update Vdd. Error: %d", dev->name, ret);
/* Set ADC VSS platdata: polarity, uV, regulator (phandle). */
ret = adc_vss_platdata_set(dev);
if (ret)
error("%s: Can't update Vss. Error: %d", dev->name, ret);
return 0;
}
UCLASS_DRIVER(adc) = {
.id = UCLASS_ADC,
.name = "adc",
.pre_probe = adc_pre_probe,
.per_device_platdata_auto_alloc_size = ADC_UCLASS_PLATDATA_SIZE,
};

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include/adc.h Normal file
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/*
* Copyright (C) 2015 Samsung Electronics
* Przemyslaw Marczak <p.marczak@samsung.com>
*
* SPDX-License-Identifier: GPL-2.0+
*/
#ifndef _ADC_H_
#define _ADC_H_
/* ADC_CHANNEL() - ADC channel bit mask, to select only required channels */
#define ADC_CHANNEL(x) (1 << x)
/* The last possible selected channel with 32-bit mask */
#define ADC_MAX_CHANNEL 31
/**
* adc_data_format: define the ADC output data format, can be useful when
* the device's input Voltage range is bipolar.
* - ADC_DATA_FORMAT_BIN - binary offset
* - ADC_DATA_FORMAT_2S - two's complement
*
* Note: Device's driver should fill the 'data_format' field of its uclass's
* platform data using one of the above data format types.
*/
enum adc_data_format {
ADC_DATA_FORMAT_BIN,
ADC_DATA_FORMAT_2S,
};
/**
* struct adc_channel - structure to hold channel conversion data.
* Useful to keep the result of a multi-channel conversion output.
*
* @id - channel id
* @data - channel conversion data
*/
struct adc_channel {
int id;
unsigned int data;
};
/**
* struct adc_uclass_platdata - basic ADC info
*
* Note: The positive/negative reference Voltage is only a name and it doesn't
* provide an information about the value polarity. It is possible, for both
* values to be a negative or positive. For this purpose the uclass's platform
* data provides a bool fields: 'vdd/vss_supply_is_negative'. This is useful,
* since the regulator API returns only a positive Voltage values.
*
* To get the reference Voltage values with polarity, use functions:
* - adc_vdd_value()
* - adc_vss_value()
* Those are useful for some cases of ADC's references, e.g.:
* * Vdd: +3.3V; Vss: -3.3V -> 6.6 Vdiff
* * Vdd: +3.3V; Vss: +0.3V -> 3.0 Vdiff
* * Vdd: +3.3V; Vss: 0.0V -> 3.3 Vdiff
* The last one is usually standard and doesn't require the fdt polarity info.
*
* For more informations read binding info:
* - doc/device-tree-bindings/adc/adc.txt
*
* @data_mask - conversion output data mask
* @data_timeout_us - single channel conversion timeout
* @multidata_timeout_us - multi channel conversion timeout
* @channel_mask - bit mask of available channels [0:31]
* @vdd_supply - positive reference Voltage supply (regulator)
* @vss_supply - negative reference Voltage supply (regulator)
* @vdd_polarity_negative - positive reference Voltage has negative polarity
* @vss_polarity_negative - negative reference Voltage has negative polarity
* @vdd_microvolts - positive reference Voltage value
* @vss_microvolts - negative reference Voltage value
*/
struct adc_uclass_platdata {
int data_format;
unsigned int data_mask;
unsigned int data_timeout_us;
unsigned int multidata_timeout_us;
unsigned int channel_mask;
struct udevice *vdd_supply;
struct udevice *vss_supply;
bool vdd_polarity_negative;
bool vss_polarity_negative;
int vdd_microvolts;
int vss_microvolts;
};
/**
* struct adc_ops - ADC device operations for single/multi-channel operation.
*/
struct adc_ops {
/**
* start_channel() - start conversion with its default parameters
* for the given channel number.
*
* @dev: ADC device to init
* @channel: analog channel number
* @return: 0 if OK, -ve on error
*/
int (*start_channel)(struct udevice *dev, int channel);
/**
* start_channels() - start conversion with its default parameters
* for the channel numbers selected by the bit mask.
*
* This is optional, useful when the hardware supports multichannel
* conversion by the single software trigger.
*
* @dev: ADC device to init
* @channel_mask: bit mask of selected analog channels
* @return: 0 if OK, -ve on error
*/
int (*start_channels)(struct udevice *dev, unsigned int channel_mask);
/**
* channel_data() - get conversion output data for the given channel.
*
* Note: The implementation of this function should only check, that
* the conversion data is available at the call time. If the hardware
* requires some delay to get the data, then this function should
* return with -EBUSY value. The ADC API will call it in a loop,
* until the data is available or the timeout expires. The maximum
* timeout for this operation is defined by the field 'data_timeout_us'
* in ADC uclasses platform data structure.
*
* @dev: ADC device to trigger
* @channel: selected analog channel number
* @data: returned pointer to selected channel's output data
* @return: 0 if OK, -EBUSY if busy, and other negative on error
*/
int (*channel_data)(struct udevice *dev, int channel,
unsigned int *data);
/**
* channels_data() - get conversion data for the selected channels.
*
* This is optional, useful when multichannel conversion is supported
* by the hardware, by the single software trigger.
*
* For the proper implementation, please look at the 'Note' for the
* above method. The only difference is in used timeout value, which
* is defined by field 'multidata_timeout_us'.
*
* @dev: ADC device to trigger
* @channel_mask: bit mask of selected analog channels
* @channels: returned pointer to array of output data for channels
* selected by the given mask
* @return: 0 if OK, -ve on error
*/
int (*channels_data)(struct udevice *dev, unsigned int channel_mask,
struct adc_channel *channels);
/**
* stop() - stop conversion of the given ADC device
*
* @dev: ADC device to stop
* @return: 0 if OK, -ve on error
*/
int (*stop)(struct udevice *dev);
};
/**
* adc_start_channel() - start conversion for given device/channel and exit.
*
* @dev: ADC device
* @channel: analog channel number
* @return: 0 if OK, -ve on error
*/
int adc_start_channel(struct udevice *dev, int channel);
/**
* adc_start_channels() - start conversion for given device/channels and exit.
*
* Note:
* To use this function, device must implement method: start_channels().
*
* @dev: ADC device to start
* @channel_mask: channel selection - a bit mask
* @channel_mask: bit mask of analog channels
* @return: 0 if OK, -ve on error
*/
int adc_start_channels(struct udevice *dev, unsigned int channel_mask);
/**
* adc_channel_data() - get conversion data for the given device channel number.
*
* @dev: ADC device to read
* @channel: analog channel number
* @data: pointer to returned channel's data
* @return: 0 if OK, -ve on error
*/
int adc_channel_data(struct udevice *dev, int channel, unsigned int *data);
/**
* adc_channels_data() - get conversion data for the channels selected by mask
*
* Note:
* To use this function, device must implement methods:
* - start_channels()
* - channels_data()
*
* @dev: ADC device to read
* @channel_mask: channel selection - a bit mask
* @channels: pointer to structure array of returned data for each channel
* @return: 0 if OK, -ve on error
*/
int adc_channels_data(struct udevice *dev, unsigned int channel_mask,
struct adc_channel *channels);
/**
* adc_data_mask() - get data mask (ADC resolution bitmask) for given ADC device
*
* This can be used if adc uclass platform data is filled.
*
* @dev: ADC device to check
* @data_mask: pointer to the returned data bitmask
* @return: 0 if OK, -ve on error
*/
int adc_data_mask(struct udevice *dev, unsigned int *data_mask);
/**
* adc_channel_single_shot() - get output data of conversion for the ADC
* device's channel. This function searches for the device with the given name,
* starts the given channel conversion and returns the output data.
*
* Note: To use this function, device must implement metods:
* - start_channel()
* - channel_data()
*
* @name: device's name to search
* @channel: device's input channel to init
* @data: pointer to conversion output data
* @return: 0 if OK, -ve on error
*/
int adc_channel_single_shot(const char *name, int channel, unsigned int *data);
/**
* adc_channels_single_shot() - get ADC conversion output data for the selected
* device's channels. This function searches for the device by the given name,
* starts the selected channels conversion and returns the output data as array
* of type 'struct adc_channel'.
*
* Note: This function can be used if device implements one of ADC's single
* or multi-channel operation API. If multi-channel operation is not supported,
* then each selected channel is triggered by the sequence start/data in a loop.
*
* @name: device's name to search
* @channel_mask: channel selection - a bit mask
* @channels: pointer to conversion output data for the selected channels
* @return: 0 if OK, -ve on error
*/
int adc_channels_single_shot(const char *name, unsigned int channel_mask,
struct adc_channel *channels);
/**
* adc_vdd_value() - get the ADC device's positive reference Voltage value
*
* Note: Depending on bool value 'vdd_supply_is_negative' of platform data,
* the returned uV value can be negative, and it's not an error.
*
* @dev: ADC device to check
* @uV: Voltage value with polarization sign (uV)
* @return: 0 on success or -ve on error
*/
int adc_vdd_value(struct udevice *dev, int *uV);
/**
* adc_vss_value() - get the ADC device's negative reference Voltage value
*
* Note: Depending on bool value 'vdd_supply_is_negative' of platform data,
* the returned uV value can be negative, and it's not an error.
*
* @dev: ADC device to check
* @uV: Voltage value with polarization sign (uV)
* @return: 0 on success or -ve on error
*/
int adc_vss_value(struct udevice *dev, int *uV);
/**
* adc_stop() - stop operation for given ADC device.
*
* @dev: ADC device to stop
* @return: 0 if OK, -ve on error
*/
int adc_stop(struct udevice *dev);
#endif

1
include/dm/uclass-id.h
View File

@ -25,6 +25,7 @@ enum uclass_id {
UCLASS_SIMPLE_BUS, /* bus with child devices */
/* U-Boot uclasses start here - in alphabetical order */
UCLASS_ADC, /* Analog-to-digital converter */
UCLASS_CLK, /* Clock source, e.g. used by peripherals */
UCLASS_CPU, /* CPU, typically part of an SoC */
UCLASS_CROS_EC, /* Chrome OS EC */