[PATCH] iio: adc: Add support for TI ADC1x8s102

[Jan Kiszka]

This is an upstream port of an IIO driver for the TI ADC108S102 and
ADC128S102. The former can be found on the Intel Galileo Gen2 and the
Siemens SIMATIC IOT2000. For those boards, ACPI-based enumeration is
included.

Original author: Bogdan Pricop <bogdan.pricop@xxxxxxxxxx>
Ported from Intel Galileo Gen2 BSP to Intel Yocto kernel:
Todor Minchev <todor@xxxxxxxxxxxxx>.

Signed-off-by: Jan Kiszka <jan.kiszka@xxxxxxxxxxx>
---
 drivers/iio/adc/Kconfig                  |  12 +
 drivers/iio/adc/Makefile                 |   1 +
 drivers/iio/adc/ti-adc1x8s102.c          | 408 +++++++++++++++++++++++++++++++
 include/linux/platform_data/adc1x8s102.h |  28 +++
 4 files changed, 449 insertions(+)
 create mode 100644 drivers/iio/adc/ti-adc1x8s102.c
 create mode 100644 include/linux/platform_data/adc1x8s102.h

diff --git a/drivers/iio/adc/Kconfig b/drivers/iio/adc/Kconfig
index dedae7adbce9..edb7254a648c 100644
--- a/drivers/iio/adc/Kconfig
+++ b/drivers/iio/adc/Kconfig
@@ -582,6 +582,18 @@ config TI_ADC128S052
 	  This driver can also be built as a module. If so, the module will be
 	  called ti-adc128s052.
 
+config TI_ADC1x8S102
+	tristate "Texas Instruments ADC1x8S102 driver"
+	depends on SPI
+	select IIO_BUFFER
+	select IIO_TRIGGERED_BUFFER
+	help
+	  Say yes here to build support for Texas Instruments ADC1x8S102 ADC.
+	  Provides direct access via sysfs.
+
+	  To compile this driver as a module, choose M here: the module will
+	  be called ti-adc1x8s102
+
 config TI_ADC161S626
 	tristate "Texas Instruments ADC161S626 1-channel differential ADC"
 	depends on SPI
diff --git a/drivers/iio/adc/Makefile b/drivers/iio/adc/Makefile
index d0012620cd1c..d5d913bc1263 100644
--- a/drivers/iio/adc/Makefile
+++ b/drivers/iio/adc/Makefile
@@ -53,6 +53,7 @@ obj-$(CONFIG_TI_ADC081C) += ti-adc081c.o
 obj-$(CONFIG_TI_ADC0832) += ti-adc0832.o
 obj-$(CONFIG_TI_ADC12138) += ti-adc12138.o
 obj-$(CONFIG_TI_ADC128S052) += ti-adc128s052.o
+obj-$(CONFIG_TI_ADC1x8S102) += ti-adc1x8s102.o
 obj-$(CONFIG_TI_ADC161S626) += ti-adc161s626.o
 obj-$(CONFIG_TI_ADS1015) += ti-ads1015.o
 obj-$(CONFIG_TI_ADS7950) += ti-ads7950.o
diff --git a/drivers/iio/adc/ti-adc1x8s102.c b/drivers/iio/adc/ti-adc1x8s102.c
new file mode 100644
index 000000000000..4f94c371489d
--- /dev/null
+++ b/drivers/iio/adc/ti-adc1x8s102.c
@@ -0,0 +1,408 @@
+/*
+ * TI ADC1x8S102 SPI ADC driver
+ *
+ * Copyright (c) 2013-2015 Intel Corporation.
+ * Copyright (c) 2017 Siemens AG
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms and conditions of the GNU General Public License,
+ * version 2, as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
+ * more details.
+ *
+ * This IIO device driver is is designed to work with the following
+ * analog to digital converters from Texas Instruments:
+ *  ADC108S102
+ *  ADC128S102
+ * The communication with ADC chip is via the SPI bus (mode 3).
+ */
+
+#include <linux/iio/iio.h>
+#include <linux/iio/buffer.h>
+#include <linux/iio/types.h>
+#include <linux/iio/triggered_buffer.h>
+#include <linux/iio/trigger_consumer.h>
+
+#include <linux/interrupt.h>
+#include <linux/module.h>
+#include <linux/spi/spi.h>
+
+#include <linux/platform_data/adc1x8s102.h>
+#include <linux/regulator/consumer.h>
+
+#include <linux/delay.h>
+#include <linux/acpi.h>
+#include <linux/property.h>
+#include <linux/gpio.h>
+
+#include <linux/spi/pxa2xx_spi.h>
+
+/*
+ * Defining the ADC resolution being 12 bits, we can use the same driver for
+ * both ADC108S102 (10 bits resolution) and ADC128S102 (12 bits resolution)
+ * chips. The ADC108S102 effectively returns a 12-bit result with the 2
+ * least-significant bits unset.
+ */
+#define ADC1x8S102_BITS		12
+#define ADC1x8S102_MAX_CHANNELS	8
+
+/* 16-bit SPI command format:
+ *   [15:14] Ignored
+ *   [13:11] 3-bit channel address
+ *   [10:0]  Ignored
+ */
+#define ADC1x8S102_CMD(ch)		(((ch) << (8)) << (3))
+
+/*
+ * 16-bit SPI response format:
+ *   [15:12] Zeros
+ *   [11:0]  12-bit ADC sample (for ADC108S102, [1:0] will always be 0).
+ */
+#define ADC1x8S102_RES_DATA(res)	(res & ((1 << ADC1x8S102_BITS) - 1))
+
+#define ADC1x8S102_GALILEO2_CS	8
+
+struct adc1x8s102_state {
+	struct spi_device		*spi;
+	struct regulator		*reg;
+	u16				ext_vin;
+	/* SPI transfer used by triggered buffer handler*/
+	struct spi_transfer		ring_xfer;
+	/* SPI transfer used by direct scan */
+	struct spi_transfer		scan_single_xfer;
+	/* SPI message used by ring_xfer SPI transfer */
+	struct spi_message		ring_msg;
+	/* SPI message used by scan_single_xfer SPI transfer */
+	struct spi_message		scan_single_msg;
+
+	/* SPI message buffers:
+	 *  tx_buf: |C0|C1|C2|C3|C4|C5|C6|C7|XX|
+	 *  rx_buf: |XX|R0|R1|R2|R3|R4|R5|R6|R7|tt|tt|tt|tt|
+	 *
+	 *  tx_buf: 8 channel read commands, plus 1 dummy command
+	 *  rx_buf: 1 dummy response, 8 channel responses, plus 64-bit timestamp
+	 */
+	__be16				rx_buf[13] ____cacheline_aligned;
+	__be16				tx_buf[9];
+};
+
+#define ADC1X8S102_V_CHAN(index)					\
+	{								\
+		.type = IIO_VOLTAGE,					\
+		.indexed = 1,						\
+		.channel = index,					\
+		.info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |		\
+			BIT(IIO_CHAN_INFO_SCALE),			\
+		.address = index,					\
+		.scan_index = index,					\
+		.scan_type = {						\
+			.sign = 'u',					\
+			.realbits = ADC1x8S102_BITS,			\
+			.storagebits = 16,				\
+			.endianness = IIO_BE,				\
+		},							\
+	}
+
+static const struct iio_chan_spec adc1x8s102_channels[] = {
+	ADC1X8S102_V_CHAN(0),
+	ADC1X8S102_V_CHAN(1),
+	ADC1X8S102_V_CHAN(2),
+	ADC1X8S102_V_CHAN(3),
+	ADC1X8S102_V_CHAN(4),
+	ADC1X8S102_V_CHAN(5),
+	ADC1X8S102_V_CHAN(6),
+	ADC1X8S102_V_CHAN(7),
+	IIO_CHAN_SOFT_TIMESTAMP(8),
+};
+
+static int adc1x8s102_update_scan_mode(struct iio_dev *indio_dev,
+		unsigned long const *active_scan_mask)
+{
+	struct adc1x8s102_state *st;
+	int i, j;
+
+	st = iio_priv(indio_dev);
+
+	/* Fill in the first x shorts of tx_buf with the number of channels
+	 * enabled for sampling by the triggered buffer
+	 */
+	for (i = 0, j = 0; i < ADC1x8S102_MAX_CHANNELS; i++) {
+		if (test_bit(i, active_scan_mask)) {
+			st->tx_buf[j] = cpu_to_be16(ADC1x8S102_CMD(i));
+			j++;
+		}
+	}
+	/* One dummy command added, to clock in the last response */
+	st->tx_buf[j] = 0x00;
+
+	/* build SPI ring message */
+	st->ring_xfer.tx_buf = &st->tx_buf[0];
+	st->ring_xfer.rx_buf = &st->rx_buf[0];
+	st->ring_xfer.len = (j + 1) * sizeof(__be16);
+
+	spi_message_init(&st->ring_msg);
+	spi_message_add_tail(&st->ring_xfer, &st->ring_msg);
+
+	return 0;
+}
+
+static irqreturn_t adc1x8s102_trigger_handler(int irq, void *p)
+{
+	struct iio_poll_func *pf = p;
+	struct iio_dev *indio_dev;
+	struct adc1x8s102_state *st;
+	s64 time_ns = 0;
+	int b_sent;
+
+	indio_dev = pf->indio_dev;
+	st = iio_priv(indio_dev);
+
+	b_sent = spi_sync(st->spi, &st->ring_msg);
+	if (b_sent == 0) {
+		if (indio_dev->scan_timestamp) {
+			time_ns = iio_get_time_ns(indio_dev);
+			memcpy((u8 *)st->rx_buf + st->ring_xfer.len, &time_ns,
+			       sizeof(time_ns));
+		}
+
+		/* Skip the dummy response in the first slot */
+		iio_push_to_buffers(indio_dev, (u8 *)&st->rx_buf[1]);
+	}
+
+	iio_trigger_notify_done(indio_dev->trig);
+
+	return IRQ_HANDLED;
+}
+
+static int adc1x8s102_scan_direct(struct adc1x8s102_state *st, unsigned int ch)
+{
+	int ret;
+
+	st->tx_buf[0] = cpu_to_be16(ADC1x8S102_CMD(ch));
+	ret = spi_sync(st->spi, &st->scan_single_msg);
+	if (ret)
+		return ret;
+
+	/* Skip the dummy response in the first slot */
+	return be16_to_cpu(st->rx_buf[1]);
+}
+
+static int adc1x8s102_read_raw(struct iio_dev *indio_dev,
+			   struct iio_chan_spec const *chan,
+			   int *val,
+			   int *val2,
+			   long m)
+{
+	int ret;
+	struct adc1x8s102_state *st;
+
+	st = iio_priv(indio_dev);
+
+	switch (m) {
+	case IIO_CHAN_INFO_RAW:
+		mutex_lock(&indio_dev->mlock);
+		if (indio_dev->currentmode == INDIO_BUFFER_TRIGGERED) {
+			ret = -EBUSY;
+			dev_warn(&st->spi->dev,
+			 "indio_dev->currentmode is INDIO_BUFFER_TRIGGERED\n");
+		} else {
+			ret = adc1x8s102_scan_direct(st, chan->address);
+		}
+		mutex_unlock(&indio_dev->mlock);
+
+		if (ret < 0)
+			return ret;
+		*val = ADC1x8S102_RES_DATA(ret);
+
+		return IIO_VAL_INT;
+	case IIO_CHAN_INFO_SCALE:
+		switch (chan->type) {
+		case IIO_VOLTAGE:
+			if (st->reg)
+				*val = regulator_get_voltage(st->reg) / 1000;
+			else
+				*val = st->ext_vin;
+
+			*val2 = chan->scan_type.realbits;
+			return IIO_VAL_FRACTIONAL_LOG2;
+		default:
+			dev_warn(&st->spi->dev,
+				 "Invalid channel type %u for channel %d\n",
+				 chan->type, chan->channel);
+			return -EINVAL;
+		}
+	default:
+		dev_warn(&st->spi->dev, "Invalid IIO_CHAN_INFO: %lu\n", m);
+		return -EINVAL;
+	}
+}
+
+static const struct iio_info adc1x8s102_info = {
+	.read_raw		= &adc1x8s102_read_raw,
+	.update_scan_mode	= &adc1x8s102_update_scan_mode,
+	.driver_module		= THIS_MODULE,
+};
+
+#ifdef CONFIG_ACPI
+typedef int (*acpi_setup_handler)(struct spi_device *,
+				  const struct adc1x8s102_platform_data **);
+
+static const struct adc1x8s102_platform_data int3495_platform_data = {
+	.ext_vin = 5000,	/* 5 V */
+};
+
+/* Galileo Gen 2 SPI setup */
+static int
+adc1x8s102_setup_int3495(struct spi_device *spi,
+			 const struct adc1x8s102_platform_data **pdata)
+{
+	struct pxa2xx_spi_chip *chip_data;
+
+	chip_data = devm_kzalloc(&spi->dev, sizeof(*chip_data), GFP_KERNEL);
+	if (!chip_data)
+		return -ENOMEM;
+
+	chip_data->gpio_cs = ADC1x8S102_GALILEO2_CS;
+	spi->controller_data = chip_data;
+	dev_info(&spi->dev, "setting GPIO CS value to %d\n",
+		 chip_data->gpio_cs);
+	spi_setup(spi);
+
+	*pdata = &int3495_platform_data;
+
+	return 0;
+}
+
+static const struct acpi_device_id adc1x8s102_acpi_ids[] = {
+	{ "INT3495",  (kernel_ulong_t)&adc1x8s102_setup_int3495 },
+	{ }
+};
+MODULE_DEVICE_TABLE(acpi, adc1x8s102_acpi_ids);
+#endif
+
+static int adc1x8s102_probe(struct spi_device *spi)
+{
+	const struct adc1x8s102_platform_data *pdata = spi->dev.platform_data;
+	struct adc1x8s102_state *st;
+	struct iio_dev *indio_dev;
+	int ret;
+
+#ifdef CONFIG_ACPI
+	if (ACPI_COMPANION(&spi->dev)) {
+		acpi_setup_handler setup_handler;
+		const struct acpi_device_id *id;
+
+		id = acpi_match_device(adc1x8s102_acpi_ids, &spi->dev);
+		if (!id)
+			return -ENODEV;
+
+		setup_handler = (acpi_setup_handler)id->driver_data;
+		if (setup_handler) {
+			ret = setup_handler(spi, &pdata);
+			if (ret)
+				return ret;
+		}
+	}
+#endif
+
+	if (!pdata) {
+		dev_err(&spi->dev, "Cannot get adc1x8s102 platform data\n");
+		return -ENODEV;
+	}
+
+	indio_dev = devm_iio_device_alloc(&spi->dev, sizeof(*st));
+	if (!indio_dev)
+		return -ENOMEM;
+
+	st = iio_priv(indio_dev);
+	st->ext_vin = pdata->ext_vin;
+
+	/* Use regulator, if available. */
+	st->reg = devm_regulator_get(&spi->dev, "vref");
+	if (IS_ERR(st->reg)) {
+		dev_err(&spi->dev, "Cannot get 'vref' regulator\n");
+		return PTR_ERR(st->reg);
+	}
+	ret = regulator_enable(st->reg);
+	if (ret < 0) {
+		dev_err(&spi->dev, "Cannot enable vref regulator\n");
+		return ret;
+	}
+
+	spi_set_drvdata(spi, indio_dev);
+	st->spi = spi;
+
+	indio_dev->name = spi->modalias;
+	indio_dev->dev.parent = &spi->dev;
+	indio_dev->modes = INDIO_DIRECT_MODE;
+	indio_dev->channels = adc1x8s102_channels;
+	indio_dev->num_channels = ARRAY_SIZE(adc1x8s102_channels);
+	indio_dev->info = &adc1x8s102_info;
+
+	/* Setup default message */
+	st->scan_single_xfer.tx_buf = st->tx_buf;
+	st->scan_single_xfer.rx_buf = st->rx_buf;
+	st->scan_single_xfer.len = 2 * sizeof(__be16);
+	st->scan_single_xfer.cs_change = 0;
+
+	spi_message_init(&st->scan_single_msg);
+	spi_message_add_tail(&st->scan_single_xfer, &st->scan_single_msg);
+
+	ret = iio_triggered_buffer_setup(indio_dev, NULL,
+			&adc1x8s102_trigger_handler, NULL);
+	if (ret)
+		goto error_disable_reg;
+
+	ret = iio_device_register(indio_dev);
+	if (ret) {
+		dev_err(&spi->dev,
+			"Failed to register IIO device\n");
+		goto error_cleanup_ring;
+	}
+	return 0;
+
+error_cleanup_ring:
+	iio_triggered_buffer_cleanup(indio_dev);
+error_disable_reg:
+	regulator_disable(st->reg);
+
+	return ret;
+}
+
+static int adc1x8s102_remove(struct spi_device *spi)
+{
+	struct iio_dev *indio_dev = spi_get_drvdata(spi);
+	struct adc1x8s102_state *st = iio_priv(indio_dev);
+
+	iio_device_unregister(indio_dev);
+	iio_triggered_buffer_cleanup(indio_dev);
+
+	regulator_disable(st->reg);
+
+	return 0;
+}
+
+static const struct spi_device_id adc1x8s102_id[] = {
+	{ "adc1x8s102", 0 },
+	{ }
+};
+MODULE_DEVICE_TABLE(spi, adc1x8s102_id);
+
+static struct spi_driver adc1x8s102_driver = {
+	.driver = {
+		.name   = "adc1x8s102",
+		.owner	= THIS_MODULE,
+		.acpi_match_table = ACPI_PTR(adc1x8s102_acpi_ids),
+	},
+	.probe		= adc1x8s102_probe,
+	.remove		= adc1x8s102_remove,
+	.id_table	= adc1x8s102_id,
+};
+module_spi_driver(adc1x8s102_driver);
+
+MODULE_AUTHOR("Bogdan Pricop <bogdan.pricop@xxxxxxxxxx>");
+MODULE_DESCRIPTION("Texas Instruments ADC1x8S102 driver");
+MODULE_LICENSE("GPL v2");
diff --git a/include/linux/platform_data/adc1x8s102.h b/include/linux/platform_data/adc1x8s102.h
new file mode 100644
index 000000000000..6ad753c99823
--- /dev/null
+++ b/include/linux/platform_data/adc1x8s102.h
@@ -0,0 +1,28 @@
+/*
+ * ADC1x8S102 SPI ADC driver
+ *
+ * Copyright(c) 2013 Intel Corporation.
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms and conditions of the GNU General Public License,
+ * version 2, as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
+ * more details.
+ */
+
+#ifndef __LINUX_PLATFORM_DATA_ADC1x8S102_H__
+#define __LINUX_PLATFORM_DATA_ADC1x8S102_H__
+
+/**
+ * struct adc1x8s102_platform_data - Platform data for the adc1x8s102 ADC driver
+ * @ext_vin: External input voltage range for all voltage input channels
+ *	This is the voltage level of pin VA in millivolts
+ **/
+struct adc1x8s102_platform_data {
+	u16  ext_vin;
+};
+
+#endif /* __LINUX_PLATFORM_DATA_ADC1x8S102_H__ */