Message-Id: <1480352295-1314-1-git-send-email-david@lechnology.com>
Date:   Mon, 28 Nov 2016 10:58:15 -0600
From:   David Lechner <david@...hnology.com>
To:     Jonathan Cameron <jic23@...nel.org>
Cc:     David Lechner <david@...hnology.com>,
        Hartmut Knaack <knaack.h@....de>,
        Lars-Peter Clausen <lars@...afoo.de>,
        Peter Meerwald-Stadler <pmeerw@...erw.net>,
        linux-kernel@...r.kernel.org, linux-iio@...r.kernel.org
Subject: [PATCH v4] iio: adc: New driver for TI ADS7950 chips

This adds a new driver for the TI ADS7950 family of ADC chips. These
communicate using SPI and come in 8/10/12-bit and 4/8/12/16 channel
varieties.

Signed-off-by: David Lechner <david@...hnology.com>
---

v4 changes:
* Change spi_async() back to spi_sync(). (I have learned that this is in a
  threaded interrupt handler, so sleeping is OK.)

v3 changes:

* Use spi_async() instead of spi_sync() in ti_ads7950_trigger_handler()
* Fix scaling in ti_ads7950_read_raw()

v2 changes:

* Got rid of XX wildcards - using ADS7950 everywhere
* Fixed some macro parentheses issues
* Added TI_ prefix to macros to match ti_ prefixes used elsewhere
* Added space in rx_buf for holding timestamp
* Use iio_device_claim_direct_mode() and spi_message_init_with_transfers()
  helper functions
* Don't use dev_info() at end of probe
* Minor spelling and code style fixes

 drivers/iio/adc/Kconfig      |  13 ++
 drivers/iio/adc/Makefile     |   1 +
 drivers/iio/adc/ti-ads7950.c | 490 +++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 504 insertions(+)
 create mode 100644 drivers/iio/adc/ti-ads7950.c

diff --git a/drivers/iio/adc/Kconfig b/drivers/iio/adc/Kconfig
index 6bbee0b..26b32f0 100644
--- a/drivers/iio/adc/Kconfig
+++ b/drivers/iio/adc/Kconfig
@@ -527,6 +527,19 @@ config TI_ADS1015
 	  This driver can also be built as a module. If so, the module will be
 	  called ti-ads1015.
 
+config TI_ADS7950
+	tristate "Texas Instruments ADS7950 ADC driver"
+	depends on SPI
+	select IIO_BUFFER
+	select IIO_TRIGGERED_BUFFER
+	help
+	  Say yes here to build support for Texas Instruments ADS7950, ADS7951,
+	  ADS7952, ADS7953, ADS7954, ADS7955, ADS7956, ADS7957, ADS7958, ADS7959.
+	  ADS7960, ADS7961.
+
+	  To compile this driver as a module, choose M here: the
+	  module will be called ti-ads7950.
+
 config TI_ADS8688
 	tristate "Texas Instruments ADS8688"
 	depends on SPI && OF
diff --git a/drivers/iio/adc/Makefile b/drivers/iio/adc/Makefile
index 9391217..1966801 100644
--- a/drivers/iio/adc/Makefile
+++ b/drivers/iio/adc/Makefile
@@ -49,6 +49,7 @@ obj-$(CONFIG_TI_ADC12138) += ti-adc12138.o
 obj-$(CONFIG_TI_ADC128S052) += ti-adc128s052.o
 obj-$(CONFIG_TI_ADC161S626) += ti-adc161s626.o
 obj-$(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_TWL4030_MADC) += twl4030-madc.o
diff --git a/drivers/iio/adc/ti-ads7950.c b/drivers/iio/adc/ti-ads7950.c
new file mode 100644
index 0000000..0330361
--- /dev/null
+++ b/drivers/iio/adc/ti-ads7950.c
@@ -0,0 +1,490 @@
+/*
+ * Texas Instruments ADS7950 SPI ADC driver
+ *
+ * Copyright 2016 David Lechner <david@...hnology.com>
+ *
+ * Based on iio/ad7923.c:
+ * Copyright 2011 Analog Devices Inc
+ * Copyright 2012 CS Systemes d'Information
+ *
+ * And also on hwmon/ads79xx.c
+ * Copyright (C) 2013 Texas Instruments Incorporated - http://www.ti.com/
+ *	Nishanth Menon
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation version 2.
+ *
+ * This program is distributed "as is" WITHOUT ANY WARRANTY of any
+ * kind, whether express or implied; without even the implied warranty
+ * of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ */
+
+#include <linux/bitops.h>
+#include <linux/device.h>
+#include <linux/err.h>
+#include <linux/interrupt.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/iio/buffer.h>
+#include <linux/iio/iio.h>
+#include <linux/iio/sysfs.h>
+#include <linux/iio/trigger_consumer.h>
+#include <linux/iio/triggered_buffer.h>
+
+#define TI_ADS7950_CR_MANUAL	BIT(12)
+#define TI_ADS7950_CR_WRITE	BIT(11)
+#define TI_ADS7950_CR_CHAN(ch)	((ch) << 7)
+#define TI_ADS7950_CR_RANGE_5V	BIT(6)
+
+#define TI_ADS7950_MAX_CHAN	16
+
+#define TI_ADS7950_TIMESTAMP_SIZE (sizeof(int64_t) / sizeof(__be16))
+
+/* val = value, dec = left shift, bits = number of bits of the mask */
+#define TI_ADS7950_EXTRACT(val, dec, bits) \
+	(((val) >> (dec)) & ((1 << (bits)) - 1))
+
+struct ti_ads7950_state {
+	struct spi_device	*spi;
+	struct spi_transfer	ring_xfer[TI_ADS7950_MAX_CHAN + 2];
+	struct spi_transfer	scan_single_xfer[3];
+	struct spi_message	ring_msg;
+	struct spi_message	scan_single_msg;
+
+	struct regulator	*reg;
+
+	unsigned int		settings;
+
+	/*
+	 * DMA (thus cache coherency maintenance) requires the
+	 * transfer buffers to live in their own cache lines.
+	 */
+	__be16	rx_buf[TI_ADS7950_MAX_CHAN + TI_ADS7950_TIMESTAMP_SIZE]
+							____cacheline_aligned;
+	__be16	tx_buf[TI_ADS7950_MAX_CHAN];
+};
+
+struct ti_ads7950_chip_info {
+	const struct iio_chan_spec *channels;
+	unsigned int num_channels;
+};
+
+enum ti_ads7950_id {
+	TI_ADS7950,
+	TI_ADS7951,
+	TI_ADS7952,
+	TI_ADS7953,
+	TI_ADS7954,
+	TI_ADS7955,
+	TI_ADS7956,
+	TI_ADS7957,
+	TI_ADS7958,
+	TI_ADS7959,
+	TI_ADS7960,
+	TI_ADS7961,
+};
+
+#define TI_ADS7950_V_CHAN(index, bits)				\
+{								\
+	.type = IIO_VOLTAGE,					\
+	.indexed = 1,						\
+	.channel = index,					\
+	.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),		\
+	.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE),	\
+	.address = index,					\
+	.datasheet_name = "CH##index",				\
+	.scan_index = index,					\
+	.scan_type = {						\
+		.sign = 'u',					\
+		.realbits = bits,				\
+		.storagebits = 16,				\
+		.shift = 12 - (bits),				\
+		.endianness = IIO_BE,				\
+	},							\
+}
+
+#define DECLARE_TI_ADS7950_4_CHANNELS(name, bits) \
+const struct iio_chan_spec name ## _channels[] = { \
+	TI_ADS7950_V_CHAN(0, bits), \
+	TI_ADS7950_V_CHAN(1, bits), \
+	TI_ADS7950_V_CHAN(2, bits), \
+	TI_ADS7950_V_CHAN(3, bits), \
+	IIO_CHAN_SOFT_TIMESTAMP(4), \
+}
+
+#define DECLARE_TI_ADS7950_8_CHANNELS(name, bits) \
+const struct iio_chan_spec name ## _channels[] = { \
+	TI_ADS7950_V_CHAN(0, bits), \
+	TI_ADS7950_V_CHAN(1, bits), \
+	TI_ADS7950_V_CHAN(2, bits), \
+	TI_ADS7950_V_CHAN(3, bits), \
+	TI_ADS7950_V_CHAN(4, bits), \
+	TI_ADS7950_V_CHAN(5, bits), \
+	TI_ADS7950_V_CHAN(6, bits), \
+	TI_ADS7950_V_CHAN(7, bits), \
+	IIO_CHAN_SOFT_TIMESTAMP(8), \
+}
+
+#define DECLARE_TI_ADS7950_12_CHANNELS(name, bits) \
+const struct iio_chan_spec name ## _channels[] = { \
+	TI_ADS7950_V_CHAN(0, bits), \
+	TI_ADS7950_V_CHAN(1, bits), \
+	TI_ADS7950_V_CHAN(2, bits), \
+	TI_ADS7950_V_CHAN(3, bits), \
+	TI_ADS7950_V_CHAN(4, bits), \
+	TI_ADS7950_V_CHAN(5, bits), \
+	TI_ADS7950_V_CHAN(6, bits), \
+	TI_ADS7950_V_CHAN(7, bits), \
+	TI_ADS7950_V_CHAN(8, bits), \
+	TI_ADS7950_V_CHAN(9, bits), \
+	TI_ADS7950_V_CHAN(10, bits), \
+	TI_ADS7950_V_CHAN(11, bits), \
+	IIO_CHAN_SOFT_TIMESTAMP(12), \
+}
+
+#define DECLARE_TI_ADS7950_16_CHANNELS(name, bits) \
+const struct iio_chan_spec name ## _channels[] = { \
+	TI_ADS7950_V_CHAN(0, bits), \
+	TI_ADS7950_V_CHAN(1, bits), \
+	TI_ADS7950_V_CHAN(2, bits), \
+	TI_ADS7950_V_CHAN(3, bits), \
+	TI_ADS7950_V_CHAN(4, bits), \
+	TI_ADS7950_V_CHAN(5, bits), \
+	TI_ADS7950_V_CHAN(6, bits), \
+	TI_ADS7950_V_CHAN(7, bits), \
+	TI_ADS7950_V_CHAN(8, bits), \
+	TI_ADS7950_V_CHAN(9, bits), \
+	TI_ADS7950_V_CHAN(10, bits), \
+	TI_ADS7950_V_CHAN(11, bits), \
+	TI_ADS7950_V_CHAN(12, bits), \
+	TI_ADS7950_V_CHAN(13, bits), \
+	TI_ADS7950_V_CHAN(14, bits), \
+	TI_ADS7950_V_CHAN(15, bits), \
+	IIO_CHAN_SOFT_TIMESTAMP(16), \
+}
+
+static DECLARE_TI_ADS7950_4_CHANNELS(ti_ads7950, 12);
+static DECLARE_TI_ADS7950_8_CHANNELS(ti_ads7951, 12);
+static DECLARE_TI_ADS7950_12_CHANNELS(ti_ads7952, 12);
+static DECLARE_TI_ADS7950_16_CHANNELS(ti_ads7953, 12);
+static DECLARE_TI_ADS7950_4_CHANNELS(ti_ads7954, 10);
+static DECLARE_TI_ADS7950_8_CHANNELS(ti_ads7955, 10);
+static DECLARE_TI_ADS7950_12_CHANNELS(ti_ads7956, 10);
+static DECLARE_TI_ADS7950_16_CHANNELS(ti_ads7957, 10);
+static DECLARE_TI_ADS7950_4_CHANNELS(ti_ads7958, 8);
+static DECLARE_TI_ADS7950_8_CHANNELS(ti_ads7959, 8);
+static DECLARE_TI_ADS7950_12_CHANNELS(ti_ads7960, 8);
+static DECLARE_TI_ADS7950_16_CHANNELS(ti_ads7961, 8);
+
+static const struct ti_ads7950_chip_info ti_ads7950_chip_info[] = {
+	[TI_ADS7950] = {
+		.channels	= ti_ads7950_channels,
+		.num_channels	= ARRAY_SIZE(ti_ads7950_channels),
+	},
+	[TI_ADS7951] = {
+		.channels	= ti_ads7951_channels,
+		.num_channels	= ARRAY_SIZE(ti_ads7951_channels),
+	},
+	[TI_ADS7952] = {
+		.channels	= ti_ads7952_channels,
+		.num_channels	= ARRAY_SIZE(ti_ads7952_channels),
+	},
+	[TI_ADS7953] = {
+		.channels	= ti_ads7953_channels,
+		.num_channels	= ARRAY_SIZE(ti_ads7953_channels),
+	},
+	[TI_ADS7954] = {
+		.channels	= ti_ads7954_channels,
+		.num_channels	= ARRAY_SIZE(ti_ads7954_channels),
+	},
+	[TI_ADS7955] = {
+		.channels	= ti_ads7955_channels,
+		.num_channels	= ARRAY_SIZE(ti_ads7955_channels),
+	},
+	[TI_ADS7956] = {
+		.channels	= ti_ads7956_channels,
+		.num_channels	= ARRAY_SIZE(ti_ads7956_channels),
+	},
+	[TI_ADS7957] = {
+		.channels	= ti_ads7957_channels,
+		.num_channels	= ARRAY_SIZE(ti_ads7957_channels),
+	},
+	[TI_ADS7958] = {
+		.channels	= ti_ads7958_channels,
+		.num_channels	= ARRAY_SIZE(ti_ads7958_channels),
+	},
+	[TI_ADS7959] = {
+		.channels	= ti_ads7959_channels,
+		.num_channels	= ARRAY_SIZE(ti_ads7959_channels),
+	},
+	[TI_ADS7960] = {
+		.channels	= ti_ads7960_channels,
+		.num_channels	= ARRAY_SIZE(ti_ads7960_channels),
+	},
+	[TI_ADS7961] = {
+		.channels	= ti_ads7961_channels,
+		.num_channels	= ARRAY_SIZE(ti_ads7961_channels),
+	},
+};
+
+/*
+ * ti_ads7950_update_scan_mode() setup the spi transfer buffer for the new
+ * scan mask
+ */
+static int ti_ads7950_update_scan_mode(struct iio_dev *indio_dev,
+				       const unsigned long *active_scan_mask)
+{
+	struct ti_ads7950_state *st = iio_priv(indio_dev);
+	int i, cmd, len;
+
+	len = 0;
+	for_each_set_bit(i, active_scan_mask, indio_dev->num_channels) {
+		cmd = TI_ADS7950_CR_WRITE | TI_ADS7950_CR_CHAN(i) | st->settings;
+		st->tx_buf[len++] = cpu_to_be16(cmd);
+	}
+
+	/* Data for the 1st channel is not returned until the 3rd transfer */
+	len += 2;
+	for (i = 0; i < len; i++) {
+		if ((i + 2) < len)
+			st->ring_xfer[i].tx_buf = &st->tx_buf[i];
+		if (i >= 2)
+			st->ring_xfer[i].rx_buf = &st->rx_buf[i - 2];
+		st->ring_xfer[i].len = 2;
+		st->ring_xfer[i].cs_change = 1;
+	}
+	/* make sure last transfer's cs_change is not set */
+	st->ring_xfer[len - 1].cs_change = 0;
+
+	spi_message_init_with_transfers(&st->ring_msg, st->ring_xfer, len);
+
+	return 0;
+}
+
+static irqreturn_t ti_ads7950_trigger_handler(int irq, void *p)
+{
+	struct iio_poll_func *pf = p;
+	struct iio_dev *indio_dev = pf->indio_dev;
+	struct ti_ads7950_state *st = iio_priv(indio_dev);
+	int ret;
+
+	ret = spi_sync(st->spi, &st->ring_msg);
+	if (ret < 0)
+		goto out;
+
+	iio_push_to_buffers_with_timestamp(indio_dev, st->rx_buf,
+					   iio_get_time_ns(indio_dev));
+
+out:
+	iio_trigger_notify_done(indio_dev->trig);
+
+	return IRQ_HANDLED;
+}
+
+static int ti_ads7950_scan_direct(struct ti_ads7950_state *st, unsigned int ch)
+{
+	int ret, cmd;
+
+	cmd = TI_ADS7950_CR_WRITE | TI_ADS7950_CR_CHAN(ch) | st->settings;
+	st->tx_buf[0] = cpu_to_be16(cmd);
+
+	ret = spi_sync(st->spi, &st->scan_single_msg);
+	if (ret)
+		return ret;
+
+	return be16_to_cpu(st->rx_buf[0]);
+}
+
+static int ti_ads7950_get_range(struct ti_ads7950_state *st)
+{
+	int vref;
+
+	vref = regulator_get_voltage(st->reg);
+	if (vref < 0)
+		return vref;
+
+	vref /= 1000;
+
+	if (st->settings & TI_ADS7950_CR_RANGE_5V)
+		vref *= 2;
+
+	return vref;
+}
+
+static int ti_ads7950_read_raw(struct iio_dev *indio_dev,
+			       struct iio_chan_spec const *chan,
+			       int *val, int *val2, long m)
+{
+	struct ti_ads7950_state *st = iio_priv(indio_dev);
+	int ret;
+
+	switch (m) {
+	case IIO_CHAN_INFO_RAW:
+
+		ret = iio_device_claim_direct_mode(indio_dev);
+		if (ret < 0)
+			return ret;
+
+		ret = ti_ads7950_scan_direct(st, chan->address);
+		iio_device_release_direct_mode(indio_dev);
+		if (ret < 0)
+			return ret;
+
+		if (chan->address != TI_ADS7950_EXTRACT(ret, 12, 4))
+			return -EIO;
+
+		*val = TI_ADS7950_EXTRACT(ret, chan->scan_type.shift,
+					  chan->scan_type.realbits);
+
+		return IIO_VAL_INT;
+	case IIO_CHAN_INFO_SCALE:
+		ret = ti_ads7950_get_range(st);
+		if (ret < 0)
+			return ret;
+
+		*val = ret;
+		*val2 = (1 << chan->scan_type.realbits) - 1;
+
+		return IIO_VAL_FRACTIONAL;
+	}
+
+	return -EINVAL;
+}
+
+static const struct iio_info ti_ads7950_info = {
+	.read_raw		= &ti_ads7950_read_raw,
+	.update_scan_mode	= ti_ads7950_update_scan_mode,
+	.driver_module		= THIS_MODULE,
+};
+
+static int ti_ads7950_probe(struct spi_device *spi)
+{
+	struct ti_ads7950_state *st;
+	struct iio_dev *indio_dev;
+	const struct ti_ads7950_chip_info *info;
+	int ret;
+
+	indio_dev = devm_iio_device_alloc(&spi->dev, sizeof(*st));
+	if (!indio_dev)
+		return -ENOMEM;
+
+	st = iio_priv(indio_dev);
+
+	spi_set_drvdata(spi, indio_dev);
+
+	st->spi = spi;
+	st->settings = TI_ADS7950_CR_MANUAL | TI_ADS7950_CR_RANGE_5V;
+
+	info = &ti_ads7950_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 = &ti_ads7950_info;
+
+	/*
+	 * Setup default message. The sample is read at the end of the first
+	 * transfer, then it takes one full cycle to convert the sample and one
+	 * more cycle to send the value. The conversion process is driven by
+	 * the SPI clock, which is why we have 3 transfers. The middle one is
+	 * just dummy data sent while the chip is converting the sample that
+	 * was read at the end of the first transfer.
+	 */
+
+	st->scan_single_xfer[0].tx_buf = &st->tx_buf[0];
+	st->scan_single_xfer[0].len = 2;
+	st->scan_single_xfer[0].cs_change = 1;
+	st->scan_single_xfer[1].tx_buf = &st->tx_buf[0];
+	st->scan_single_xfer[1].len = 2;
+	st->scan_single_xfer[1].cs_change = 1;
+	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, "refin");
+	if (IS_ERR(st->reg)) {
+		dev_err(&spi->dev, "Failed get get regulator \"refin\"\n");
+		return PTR_ERR(st->reg);
+	}
+
+	ret = regulator_enable(st->reg);
+	if (ret) {
+		dev_err(&spi->dev, "Failed to enable regulator \"refin\"\n");
+		return ret;
+	}
+
+	ret = iio_triggered_buffer_setup(indio_dev, NULL,
+					 &ti_ads7950_trigger_handler, NULL);
+	if (ret) {
+		dev_err(&spi->dev, "Failed to setup triggered buffer\n");
+		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 ti_ads7950_remove(struct spi_device *spi)
+{
+	struct iio_dev *indio_dev = spi_get_drvdata(spi);
+	struct ti_ads7950_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 ti_ads7950_id[] = {
+	{"ti-ads7950", TI_ADS7950},
+	{"ti-ads7951", TI_ADS7951},
+	{"ti-ads7952", TI_ADS7952},
+	{"ti-ads7953", TI_ADS7953},
+	{"ti-ads7954", TI_ADS7954},
+	{"ti-ads7955", TI_ADS7955},
+	{"ti-ads7956", TI_ADS7956},
+	{"ti-ads7957", TI_ADS7957},
+	{"ti-ads7958", TI_ADS7958},
+	{"ti-ads7959", TI_ADS7959},
+	{"ti-ads7960", TI_ADS7960},
+	{"ti-ads7961", TI_ADS7961},
+	{ }
+};
+MODULE_DEVICE_TABLE(spi, ti_ads7950_id);
+
+static struct spi_driver ti_ads7950_driver = {
+	.driver = {
+		.name	= "ti-ads7950",
+	},
+	.probe		= ti_ads7950_probe,
+	.remove		= ti_ads7950_remove,
+	.id_table	= ti_ads7950_id,
+};
+module_spi_driver(ti_ads7950_driver);
+
+MODULE_AUTHOR("David Lechner <david@...hnology.com>");
+MODULE_DESCRIPTION("TI TI_ADS7950 ADC");
+MODULE_LICENSE("GPL v2");
-- 
2.7.4

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