iio: adc: tlc4541: add support for TI tlc4541 adc

This adds TI's tlc4541 16-bit ADC driver. Which is a single channel
ADC. Supports raw and trigger buffer access.
Also supports the tlc3541 14-bit device, which has not been tested.
Implementation of the tlc3541 is fairly straight forward thou.

Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Phil Reid <preid@electromag.com.au>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

drivers/iio/adc/Kconfig

@@ -612,6 +612,18 @@ config TI_AM335X_ADC
 	  To compile this driver as a module, choose M here: the module will be
 	  called ti_am335x_adc.
 
+config TI_TLC4541
+	tristate "Texas Instruments TLC4541 ADC driver"
+	depends on SPI
+	select IIO_BUFFER
+	select IIO_TRIGGERED_BUFFER
+	help
+	  Say yes here to build support for Texas Instruments TLC4541 / TLC3541
+	  ADC chips.
+
+	  This driver can also be built as a module. If so, the module will be
+	  called ti-tlc4541.
+
 config TWL4030_MADC
 	tristate "TWL4030 MADC (Monitoring A/D Converter)"
 	depends on TWL4030_CORE

drivers/iio/adc/Makefile

@@ -56,6 +56,7 @@ obj-$(CONFIG_TI_ADS1015) += ti-ads1015.o
 obj-$(CONFIG_TI_ADS7950) += ti-ads7950.o
 obj-$(CONFIG_TI_ADS8688) += ti-ads8688.o
 obj-$(CONFIG_TI_AM335X_ADC) += ti_am335x_adc.o
+obj-$(CONFIG_TI_TLC4541) += ti-tlc4541.o
 obj-$(CONFIG_TWL4030_MADC) += twl4030-madc.o
 obj-$(CONFIG_TWL6030_GPADC) += twl6030-gpadc.o
 obj-$(CONFIG_VF610_ADC) += vf610_adc.o

drivers/iio/adc/max11100.c

@@ -30,7 +30,6 @@
 #define MAX11100_LSB_DIV		(1 << 16)
 
 struct max11100_state {
-	const struct max11100_chip_desc *desc;
 	struct regulator *vref_reg;
 	struct spi_device *spi;
 
@@ -49,14 +48,6 @@ static struct iio_chan_spec max11100_channels[] = {
 	},
 };
 
-static struct max11100_chip_desc {
-	unsigned int num_chan;
-	const struct iio_chan_spec *channels;
-} max11100_desc = {
-	.num_chan = ARRAY_SIZE(max11100_channels),
-	.channels = max11100_channels,
-};
-
 static int max11100_read_single(struct iio_dev *indio_dev, int *val)
 {
 	int ret;
@@ -127,15 +118,14 @@ static int max11100_probe(struct spi_device *spi)
 
 	state = iio_priv(indio_dev);
 	state->spi = spi;
-	state->desc = &max11100_desc;
 
 	indio_dev->dev.parent = &spi->dev;
 	indio_dev->dev.of_node = spi->dev.of_node;
 	indio_dev->name = "max11100";
 	indio_dev->info = &max11100_info;
 	indio_dev->modes = INDIO_DIRECT_MODE;
-	indio_dev->channels = state->desc->channels;
-	indio_dev->num_channels = state->desc->num_chan;
+	indio_dev->channels = max11100_channels,
+	indio_dev->num_channels = ARRAY_SIZE(max11100_channels),
 
 	state->vref_reg = devm_regulator_get(&spi->dev, "vref");
 	if (IS_ERR(state->vref_reg))
@@ -162,9 +152,8 @@ static int max11100_remove(struct spi_device *spi)
 	struct iio_dev *indio_dev = spi_get_drvdata(spi);
 	struct max11100_state *state = iio_priv(indio_dev);
 
-	regulator_disable(state->vref_reg);
-
 	iio_device_unregister(indio_dev);
+	regulator_disable(state->vref_reg);
 
 	return 0;
 }

drivers/iio/adc/ti-tlc4541.c

@@ -0,0 +1,271 @@
+/*
+ * TI tlc4541 ADC Driver
+ *
+ * Copyright (C) 2017 Phil Reid
+ *
+ * Datasheets can be found here:
+ * http://www.ti.com/lit/gpn/tlc3541
+ * http://www.ti.com/lit/gpn/tlc4541
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ * The tlc4541 requires 24 clock cycles to start a transfer.
+ * Conversion then takes 2.94us to complete before data is ready
+ * Data is returned MSB first.
+ */
+
+#include <linux/delay.h>
+#include <linux/device.h>
+#include <linux/err.h>
+#include <linux/interrupt.h>
+#include <linux/iio/iio.h>
+#include <linux/iio/sysfs.h>
+#include <linux/iio/buffer.h>
+#include <linux/iio/trigger_consumer.h>
+#include <linux/iio/triggered_buffer.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/regulator/consumer.h>
+#include <linux/slab.h>
+#include <linux/spi/spi.h>
+#include <linux/sysfs.h>
+
+struct tlc4541_state {
+	struct spi_device               *spi;
+	struct regulator                *reg;
+	struct spi_transfer             scan_single_xfer[3];
+	struct spi_message              scan_single_msg;
+
+	/*
+	 * DMA (thus cache coherency maintenance) requires the
+	 * transfer buffers to live in their own cache lines.
+	 * 2 bytes data + 6 bytes padding + 8 bytes timestamp when
+	 * call iio_push_to_buffers_with_timestamp.
+	 */
+	__be16                          rx_buf[8] ____cacheline_aligned;
+};
+
+struct tlc4541_chip_info {
+	const struct iio_chan_spec *channels;
+	unsigned int num_channels;
+};
+
+enum tlc4541_id {
+	TLC3541,
+	TLC4541,
+};
+
+#define TLC4541_V_CHAN(bits, bitshift) {                              \
+		.type = IIO_VOLTAGE,                                  \
+		.info_mask_separate       = BIT(IIO_CHAN_INFO_RAW),   \
+		.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE), \
+		.scan_type = {                                        \
+			.sign = 'u',                                  \
+			.realbits = (bits),                           \
+			.storagebits = 16,                            \
+			.shift = (bitshift),                          \
+			.endianness = IIO_BE,                         \
+		},                                                    \
+	}
+
+#define DECLARE_TLC4541_CHANNELS(name, bits, bitshift) \
+const struct iio_chan_spec name ## _channels[] = { \
+	TLC4541_V_CHAN(bits, bitshift), \
+	IIO_CHAN_SOFT_TIMESTAMP(1), \
+}
+
+static DECLARE_TLC4541_CHANNELS(tlc3541, 14, 2);
+static DECLARE_TLC4541_CHANNELS(tlc4541, 16, 0);
+
+static const struct tlc4541_chip_info tlc4541_chip_info[] = {
+	[TLC3541] = {
+		.channels = tlc3541_channels,
+		.num_channels = ARRAY_SIZE(tlc3541_channels),
+	},
+	[TLC4541] = {
+		.channels = tlc4541_channels,
+		.num_channels = ARRAY_SIZE(tlc4541_channels),
+	},
+};
+
+static irqreturn_t tlc4541_trigger_handler(int irq, void *p)
+{
+	struct iio_poll_func *pf = p;
+	struct iio_dev *indio_dev = pf->indio_dev;
+	struct tlc4541_state *st = iio_priv(indio_dev);
+	int ret;
+
+	ret = spi_sync(st->spi, &st->scan_single_msg);
+	if (ret < 0)
+		goto done;
+
+	iio_push_to_buffers_with_timestamp(indio_dev, st->rx_buf,
+					   iio_get_time_ns(indio_dev));
+
+done:
+	iio_trigger_notify_done(indio_dev->trig);
+	return IRQ_HANDLED;
+}
+
+static int tlc4541_get_range(struct tlc4541_state *st)
+{
+	int vref;
+
+	vref = regulator_get_voltage(st->reg);
+	if (vref < 0)
+		return vref;
+
+	vref /= 1000;
+
+	return vref;
+}
+
+static int tlc4541_read_raw(struct iio_dev *indio_dev,
+			    struct iio_chan_spec const *chan,
+			    int *val,
+			    int *val2,
+			    long m)
+{
+	int ret = 0;
+	struct tlc4541_state *st = iio_priv(indio_dev);
+
+	switch (m) {
+	case IIO_CHAN_INFO_RAW:
+		ret = iio_device_claim_direct_mode(indio_dev);
+		if (ret)
+			return ret;
+		ret = spi_sync(st->spi, &st->scan_single_msg);
+		iio_device_release_direct_mode(indio_dev);
+		if (ret < 0)
+			return ret;
+		*val = be16_to_cpu(st->rx_buf[0]);
+		*val = *val >> chan->scan_type.shift;
+		*val &= GENMASK(chan->scan_type.realbits - 1, 0);
+		return IIO_VAL_INT;
+	case IIO_CHAN_INFO_SCALE:
+		ret = tlc4541_get_range(st);
+		if (ret < 0)
+			return ret;
+		*val = ret;
+		*val2 = chan->scan_type.realbits;
+		return IIO_VAL_FRACTIONAL_LOG2;
+	}
+	return -EINVAL;
+}
+
+static const struct iio_info tlc4541_info = {
+	.read_raw = &tlc4541_read_raw,
+	.driver_module = THIS_MODULE,
+};
+
+static int tlc4541_probe(struct spi_device *spi)
+{
+	struct tlc4541_state *st;
+	struct iio_dev *indio_dev;
+	const struct tlc4541_chip_info *info;
+	int ret;
+	int8_t device_init = 0;
+
+	indio_dev = devm_iio_device_alloc(&spi->dev, sizeof(*st));
+	if (indio_dev == NULL)
+		return -ENOMEM;
+
+	st = iio_priv(indio_dev);
+
+	spi_set_drvdata(spi, indio_dev);
+
+	st->spi = spi;
+
+	info = &tlc4541_chip_info[spi_get_device_id(spi)->driver_data];
+
+	indio_dev->name = spi_get_device_id(spi)->name;
+	indio_dev->dev.parent = &spi->dev;
+	indio_dev->modes = INDIO_DIRECT_MODE;
+	indio_dev->channels = info->channels;
+	indio_dev->num_channels = info->num_channels;
+	indio_dev->info = &tlc4541_info;
+
+	/* perform reset */
+	spi_write(spi, &device_init, 1);
+
+	/* Setup default message */
+	st->scan_single_xfer[0].rx_buf = &st->rx_buf[0];
+	st->scan_single_xfer[0].len = 3;
+	st->scan_single_xfer[1].delay_usecs = 3;
+	st->scan_single_xfer[2].rx_buf = &st->rx_buf[0];
+	st->scan_single_xfer[2].len = 2;
+
+	spi_message_init_with_transfers(&st->scan_single_msg,
+					st->scan_single_xfer, 3);
+
+	st->reg = devm_regulator_get(&spi->dev, "vref");
+	if (IS_ERR(st->reg))
+		return PTR_ERR(st->reg);
+
+	ret = regulator_enable(st->reg);
+	if (ret)
+		return ret;
+
+	ret = iio_triggered_buffer_setup(indio_dev, NULL,
+			&tlc4541_trigger_handler, NULL);
+	if (ret)
+		goto error_disable_reg;
+
+	ret = iio_device_register(indio_dev);
+	if (ret)
+		goto error_cleanup_buffer;
+
+	return 0;
+
+error_cleanup_buffer:
+	iio_triggered_buffer_cleanup(indio_dev);
+error_disable_reg:
+	regulator_disable(st->reg);
+
+	return ret;
+}
+
+static int tlc4541_remove(struct spi_device *spi)
+{
+	struct iio_dev *indio_dev = spi_get_drvdata(spi);
+	struct tlc4541_state *st = iio_priv(indio_dev);
+
+	iio_device_unregister(indio_dev);
+	iio_triggered_buffer_cleanup(indio_dev);
+	regulator_disable(st->reg);
+
+	return 0;
+}
+
+#ifdef CONFIG_OF
+static const struct of_device_id tlc4541_dt_ids[] = {
+	{ .compatible = "ti,tlc3541", },
+	{ .compatible = "ti,tlc4541", },
+	{}
+};
+MODULE_DEVICE_TABLE(of, tlc4541_dt_ids);
+#endif
+
+static const struct spi_device_id tlc4541_id[] = {
+	{"tlc3541", TLC3541},
+	{"tlc4541", TLC4541},
+	{}
+};
+MODULE_DEVICE_TABLE(spi, tlc4541_id);
+
+static struct spi_driver tlc4541_driver = {
+	.driver = {
+		.name   = "tlc4541",
+		.of_match_table = of_match_ptr(tlc4541_dt_ids),
+	},
+	.probe          = tlc4541_probe,
+	.remove         = tlc4541_remove,
+	.id_table       = tlc4541_id,
+};
+module_spi_driver(tlc4541_driver);
+
+MODULE_AUTHOR("Phil Reid <preid@electromag.com.au>");
+MODULE_DESCRIPTION("Texas Instruments TLC4541 ADC");
+MODULE_LICENSE("GPL v2");