ti-ads8344.c

  1// SPDX-License-Identifier: GPL-2.0+
  2/*
  3 * ADS8344 16-bit 8-Channel ADC driver
  4 *
  5 * Author: Gregory CLEMENT <gregory.clement@bootlin.com>
  6 *
  7 * Datasheet: https://www.ti.com/lit/ds/symlink/ads8344.pdf
  8 */
  9
 10#include <linux/delay.h>
 11#include <linux/iio/buffer.h>
 12#include <linux/iio/iio.h>
 13#include <linux/module.h>
 14#include <linux/regulator/consumer.h>
 15#include <linux/spi/spi.h>
 16
 17#define ADS8344_START BIT(7)
 18#define ADS8344_SINGLE_END BIT(2)
 19#define ADS8344_CHANNEL(channel) ((channel) << 4)
 20#define ADS8344_CLOCK_INTERNAL 0x2 /* PD1 = 1 and PD0 = 0 */
 21
 22struct ads8344 {
 23	struct spi_device *spi;
 24	struct regulator *reg;
 25	/*
 26	 * Lock protecting access to adc->tx_buff and rx_buff,
 27	 * especially from concurrent read on sysfs file.
 28	 */
 29	struct mutex lock;
 30
 31	u8 tx_buf __aligned(IIO_DMA_MINALIGN);
 32	u8 rx_buf[3];
 33};
 34
 35#define ADS8344_VOLTAGE_CHANNEL(chan, addr)				\
 36	{								\
 37		.type = IIO_VOLTAGE,					\
 38		.indexed = 1,						\
 39		.channel = chan,					\
 40		.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),		\
 41		.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE),	\
 42		.address = addr,					\
 43	}
 44
 45#define ADS8344_VOLTAGE_CHANNEL_DIFF(chan1, chan2, addr)		\
 46	{								\
 47		.type = IIO_VOLTAGE,					\
 48		.indexed = 1,						\
 49		.channel = (chan1),					\
 50		.channel2 = (chan2),					\
 51		.differential = 1,					\
 52		.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),		\
 53		.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE),	\
 54		.address = addr,					\
 55	}
 56
 57static const struct iio_chan_spec ads8344_channels[] = {
 58	ADS8344_VOLTAGE_CHANNEL(0, 0),
 59	ADS8344_VOLTAGE_CHANNEL(1, 4),
 60	ADS8344_VOLTAGE_CHANNEL(2, 1),
 61	ADS8344_VOLTAGE_CHANNEL(3, 5),
 62	ADS8344_VOLTAGE_CHANNEL(4, 2),
 63	ADS8344_VOLTAGE_CHANNEL(5, 6),
 64	ADS8344_VOLTAGE_CHANNEL(6, 3),
 65	ADS8344_VOLTAGE_CHANNEL(7, 7),
 66	ADS8344_VOLTAGE_CHANNEL_DIFF(0, 1, 8),
 67	ADS8344_VOLTAGE_CHANNEL_DIFF(2, 3, 9),
 68	ADS8344_VOLTAGE_CHANNEL_DIFF(4, 5, 10),
 69	ADS8344_VOLTAGE_CHANNEL_DIFF(6, 7, 11),
 70	ADS8344_VOLTAGE_CHANNEL_DIFF(1, 0, 12),
 71	ADS8344_VOLTAGE_CHANNEL_DIFF(3, 2, 13),
 72	ADS8344_VOLTAGE_CHANNEL_DIFF(5, 4, 14),
 73	ADS8344_VOLTAGE_CHANNEL_DIFF(7, 6, 15),
 74};
 75
 76static int ads8344_adc_conversion(struct ads8344 *adc, int channel,
 77				  bool differential)
 78{
 79	struct spi_device *spi = adc->spi;
 80	int ret;
 81
 82	adc->tx_buf = ADS8344_START;
 83	if (!differential)
 84		adc->tx_buf |= ADS8344_SINGLE_END;
 85	adc->tx_buf |= ADS8344_CHANNEL(channel);
 86	adc->tx_buf |= ADS8344_CLOCK_INTERNAL;
 87
 88	ret = spi_write(spi, &adc->tx_buf, 1);
 89	if (ret)
 90		return ret;
 91
 92	udelay(9);
 93
 94	ret = spi_read(spi, adc->rx_buf, sizeof(adc->rx_buf));
 95	if (ret)
 96		return ret;
 97
 98	return adc->rx_buf[0] << 9 | adc->rx_buf[1] << 1 | adc->rx_buf[2] >> 7;
 99}
100
101static int ads8344_read_raw(struct iio_dev *iio,
102			    struct iio_chan_spec const *channel, int *value,
103			    int *shift, long mask)
104{
105	struct ads8344 *adc = iio_priv(iio);
106
107	switch (mask) {
108	case IIO_CHAN_INFO_RAW:
109		mutex_lock(&adc->lock);
110		*value = ads8344_adc_conversion(adc, channel->address,
111						channel->differential);
112		mutex_unlock(&adc->lock);
113		if (*value < 0)
114			return *value;
115
116		return IIO_VAL_INT;
117	case IIO_CHAN_INFO_SCALE:
118		*value = regulator_get_voltage(adc->reg);
119		if (*value < 0)
120			return *value;
121
122		/* convert regulator output voltage to mV */
123		*value /= 1000;
124		*shift = 16;
125
126		return IIO_VAL_FRACTIONAL_LOG2;
127	default:
128		return -EINVAL;
129	}
130}
131
132static const struct iio_info ads8344_info = {
133	.read_raw = ads8344_read_raw,
134};
135
136static void ads8344_reg_disable(void *data)
137{
138	regulator_disable(data);
139}
140
141static int ads8344_probe(struct spi_device *spi)
142{
143	struct iio_dev *indio_dev;
144	struct ads8344 *adc;
145	int ret;
146
147	indio_dev = devm_iio_device_alloc(&spi->dev, sizeof(*adc));
148	if (!indio_dev)
149		return -ENOMEM;
150
151	adc = iio_priv(indio_dev);
152	adc->spi = spi;
153	mutex_init(&adc->lock);
154
155	indio_dev->name = dev_name(&spi->dev);
156	indio_dev->info = &ads8344_info;
157	indio_dev->modes = INDIO_DIRECT_MODE;
158	indio_dev->channels = ads8344_channels;
159	indio_dev->num_channels = ARRAY_SIZE(ads8344_channels);
160
161	adc->reg = devm_regulator_get(&spi->dev, "vref");
162	if (IS_ERR(adc->reg))
163		return PTR_ERR(adc->reg);
164
165	ret = regulator_enable(adc->reg);
166	if (ret)
167		return ret;
168
169	ret = devm_add_action_or_reset(&spi->dev, ads8344_reg_disable, adc->reg);
170	if (ret)
171		return ret;
172
173	return devm_iio_device_register(&spi->dev, indio_dev);
174}
175
176static const struct of_device_id ads8344_of_match[] = {
177	{ .compatible = "ti,ads8344", },
178	{ }
179};
180MODULE_DEVICE_TABLE(of, ads8344_of_match);
181
182static struct spi_driver ads8344_driver = {
183	.driver = {
184		.name = "ads8344",
185		.of_match_table = ads8344_of_match,
186	},
187	.probe = ads8344_probe,
188};
189module_spi_driver(ads8344_driver);
190
191MODULE_AUTHOR("Gregory CLEMENT <gregory.clement@bootlin.com>");
192MODULE_DESCRIPTION("ADS8344 driver");
193MODULE_LICENSE("GPL");