dm: adc: add simple ADC uclass implementation

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>

2 files changed, 289 insertions, 0 deletions

diff --git a/include/adc.h b/include/adc.h
new file mode 100644
index 0000000..4b14017
--- /dev/null
+++ b/include/adc.h
@@ -0,0 +1,288 @@
+/*
+ * 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
diff --git a/include/dm/uclass-id.h b/include/dm/uclass-id.h
index 886a44c..d0cf4ce 100644
--- a/include/dm/uclass-id.h
+++ b/include/dm/uclass-id.h
@@ -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 */