IIO ADC support for AD7923

This patch adds support for Analog Devices AD7923 ADC in the IIO Subsystem.

Signed-off-by: Patrick Vasseur <patrick.vasseur@c-s.fr>
Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
Reviewed-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

3 files changed, 311 insertions, 0 deletions

diff --git a/drivers/iio/adc/Kconfig b/drivers/iio/adc/Kconfig
index e372257a8494..00213eaf8aa9 100644
--- a/drivers/iio/adc/Kconfig
+++ b/drivers/iio/adc/Kconfig
@@ -30,6 +30,18 @@ config AD7298
           To compile this driver as a module, choose M here: the
           module will be called ad7298.
 
+config AD7923
+        tristate "Analog Devices AD7923 ADC driver"
+        depends on SPI
+        select IIO_BUFFER
+        select IIO_TRIGGERED_BUFFER
+        help
+          Say yes here to build support for Analog Devices AD7923
+          4 Channel ADC with temperature sensor.
+
+          To compile this driver as a module, choose M here: the
+          module will be called ad7923.
+
 config AD7791
         tristate "Analog Devices AD7791 ADC driver"
         depends on SPI
diff --git a/drivers/iio/adc/Makefile b/drivers/iio/adc/Makefile
index 2d5f10080d8d..ab910ba4664c 100644
--- a/drivers/iio/adc/Makefile
+++ b/drivers/iio/adc/Makefile
@@ -5,6 +5,7 @@
 obj-$(CONFIG_AD_SIGMA_DELTA) += ad_sigma_delta.o
 obj-$(CONFIG_AD7266) += ad7266.o
 obj-$(CONFIG_AD7298) += ad7298.o
+obj-$(CONFIG_AD7923) += ad7923.o
 obj-$(CONFIG_AD7476) += ad7476.o
 obj-$(CONFIG_AD7791) += ad7791.o
 obj-$(CONFIG_AD7793) += ad7793.o
diff --git a/drivers/iio/adc/ad7923.c b/drivers/iio/adc/ad7923.c
new file mode 100644
index 000000000000..28b2bda8f0ec
--- /dev/null
+++ b/drivers/iio/adc/ad7923.c
@@ -0,0 +1,298 @@
+/*
+ * AD7923 SPI ADC driver
+ *
+ * Copyright 2011 Analog Devices Inc (from AD7923 Driver)
+ * Copyright 2012 CS Systemes d'Information
+ *
+ * Licensed under the GPL-2.
+ */
+
+#include <linux/device.h>
+#include <linux/kernel.h>
+#include <linux/slab.h>
+#include <linux/sysfs.h>
+#include <linux/spi/spi.h>
+#include <linux/err.h>
+#include <linux/delay.h>
+#include <linux/module.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>
+
+#define AD7923_WRITE_CR         (1 << 11)       /* write control register */
+#define AD7923_RANGE            (1 << 1)        /* range to REFin */
+#define AD7923_CODING           (1 << 0)        /* coding is straight binary */
+#define AD7923_PM_MODE_AS       (1)             /* auto shutdown */
+#define AD7923_PM_MODE_FS       (2)             /* full shutdown */
+#define AD7923_PM_MODE_OPS      (3)             /* normal operation */
+#define AD7923_CHANNEL_0        (0)             /* analog input 0 */
+#define AD7923_CHANNEL_1        (1)             /* analog input 1 */
+#define AD7923_CHANNEL_2        (2)             /* analog input 2 */
+#define AD7923_CHANNEL_3        (3)             /* analog input 3 */
+#define AD7923_SEQUENCE_OFF     (0)             /* no sequence fonction */
+#define AD7923_SEQUENCE_PROTECT (2)             /* no interrupt write cycle */
+#define AD7923_SEQUENCE_ON      (3)             /* continuous sequence */
+
+#define AD7923_MAX_CHAN         4
+
+#define AD7923_PM_MODE_WRITE(mode)      (mode << 4)     /* write mode */
+#define AD7923_CHANNEL_WRITE(channel)   (channel << 6)  /* write channel */
+#define AD7923_SEQUENCE_WRITE(sequence) (((sequence & 1) << 3) \
+                                        + ((sequence & 2) << 9))
+                                                /* write sequence fonction */
+/* left shift for CR : bit 11 transmit in first */
+#define AD7923_SHIFT_REGISTER   4
+
+/* val = value, dec = left shift, bits = number of bits of the mask */
+#define EXTRACT(val, dec, bits)         ((val >> dec) & ((1 << bits) - 1))
+
+struct ad7923_state {
+        struct spi_device               *spi;
+        struct spi_transfer             ring_xfer[5];
+        struct spi_transfer             scan_single_xfer[2];
+        struct spi_message              ring_msg;
+        struct spi_message              scan_single_msg;
+        /*
+         * DMA (thus cache coherency maintenance) requires the
+         * transfer buffers to live in their own cache lines.
+         */
+        __be16                          rx_buf[4] ____cacheline_aligned;
+        __be16                          tx_buf[4];
+};
+
+#define AD7923_V_CHAN(index)                                            \
+        {                                                               \
+                .type = IIO_VOLTAGE,                                    \
+                .indexed = 1,                                           \
+                .channel = index,                                       \
+                .info_mask = IIO_CHAN_INFO_RAW_SEPARATE_BIT |           \
+                IIO_CHAN_INFO_SCALE_SHARED_BIT,                         \
+                .address = index,                                       \
+                .scan_index = index,                                    \
+                .scan_type = {                                          \
+                        .sign = 'u',                                    \
+                        .realbits = 12,                                 \
+                        .storagebits = 16,                              \
+                        .endianness = IIO_BE,                           \
+                },                                                      \
+        }
+
+static const struct iio_chan_spec ad7923_channels[] = {
+        AD7923_V_CHAN(0),
+        AD7923_V_CHAN(1),
+        AD7923_V_CHAN(2),
+        AD7923_V_CHAN(3),
+        IIO_CHAN_SOFT_TIMESTAMP(4),
+};
+
+/**
+ * ad7923_update_scan_mode() setup the spi transfer buffer for the new scan mask
+ **/
+static int ad7923_update_scan_mode(struct iio_dev *indio_dev,
+        const unsigned long *active_scan_mask)
+{
+        struct ad7923_state *st = iio_priv(indio_dev);
+        int i, cmd, len;
+
+        len = 0;
+        for_each_set_bit(i, active_scan_mask, AD7923_MAX_CHAN) {
+                cmd = AD7923_WRITE_CR | AD7923_CODING | AD7923_RANGE |
+                        AD7923_PM_MODE_WRITE(AD7923_PM_MODE_OPS) |
+                        AD7923_SEQUENCE_WRITE(AD7923_SEQUENCE_OFF) |
+                        AD7923_CHANNEL_WRITE(i);
+                cmd <<= AD7923_SHIFT_REGISTER;
+                st->tx_buf[len++] = cpu_to_be16(cmd);
+        }
+        /* build spi ring message */
+        st->ring_xfer[0].tx_buf = &st->tx_buf[0];
+        st->ring_xfer[0].len = len;
+        st->ring_xfer[0].cs_change = 1;
+
+        spi_message_init(&st->ring_msg);
+        spi_message_add_tail(&st->ring_xfer[0], &st->ring_msg);
+
+        for (i = 0; i < len; i++) {
+                st->ring_xfer[i + 1].rx_buf = &st->rx_buf[i];
+                st->ring_xfer[i + 1].len = 2;
+                st->ring_xfer[i + 1].cs_change = 1;
+                spi_message_add_tail(&st->ring_xfer[i + 1], &st->ring_msg);
+        }
+        /* make sure last transfer cs_change is not set */
+        st->ring_xfer[i + 1].cs_change = 0;
+
+        return 0;
+}
+
+/**
+ * ad7923_trigger_handler() bh of trigger launched polling to ring buffer
+ *
+ * Currently there is no option in this driver to disable the saving of
+ * timestamps within the ring.
+ **/
+static irqreturn_t ad7923_trigger_handler(int irq, void *p)
+{
+        struct iio_poll_func *pf = p;
+        struct iio_dev *indio_dev = pf->indio_dev;
+        struct ad7923_state *st = iio_priv(indio_dev);
+        s64 time_ns = 0;
+        int b_sent;
+
+        b_sent = spi_sync(st->spi, &st->ring_msg);
+        if (b_sent)
+                goto done;
+
+        if (indio_dev->scan_timestamp) {
+                time_ns = iio_get_time_ns();
+                memcpy((u8 *)st->rx_buf + indio_dev->scan_bytes - sizeof(s64),
+                        &time_ns, sizeof(time_ns));
+        }
+
+        iio_push_to_buffers(indio_dev, (u8 *)st->rx_buf);
+
+done:
+        iio_trigger_notify_done(indio_dev->trig);
+
+        return IRQ_HANDLED;
+}
+
+static int ad7923_scan_direct(struct ad7923_state *st, unsigned ch)
+{
+        int ret, cmd;
+
+        cmd = AD7923_WRITE_CR | AD7923_PM_MODE_WRITE(AD7923_PM_MODE_OPS) |
+                AD7923_SEQUENCE_WRITE(AD7923_SEQUENCE_OFF) | AD7923_CODING |
+                AD7923_CHANNEL_WRITE(ch) | AD7923_RANGE;
+        cmd <<= AD7923_SHIFT_REGISTER;
+        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 ad7923_read_raw(struct iio_dev *indio_dev,
+                           struct iio_chan_spec const *chan,
+                           int *val,
+                           int *val2,
+                           long m)
+{
+        int ret;
+        struct ad7923_state *st = iio_priv(indio_dev);
+
+        switch (m) {
+        case IIO_CHAN_INFO_RAW:
+                mutex_lock(&indio_dev->mlock);
+                if (iio_buffer_enabled(indio_dev))
+                        ret = -EBUSY;
+                else
+                        ret = ad7923_scan_direct(st, chan->address);
+                mutex_unlock(&indio_dev->mlock);
+
+                if (ret < 0)
+                        return ret;
+
+                if (chan->address == EXTRACT(ret, 12, 4))
+                        *val = EXTRACT(ret, 0, 12);
+
+                return IIO_VAL_INT;
+        }
+        return -EINVAL;
+}
+
+static const struct iio_info ad7923_info = {
+        .read_raw = &ad7923_read_raw,
+        .update_scan_mode = ad7923_update_scan_mode,
+        .driver_module = THIS_MODULE,
+};
+
+static int ad7923_probe(struct spi_device *spi)
+{
+        struct ad7923_state *st;
+        struct iio_dev *indio_dev = iio_device_alloc(sizeof(*st));
+        int ret;
+
+        if (indio_dev == NULL)
+                return -ENOMEM;
+
+        st = iio_priv(indio_dev);
+
+        spi_set_drvdata(spi, indio_dev);
+
+        st->spi = spi;
+
+        indio_dev->name = spi_get_device_id(spi)->name;
+        indio_dev->dev.parent = &spi->dev;
+        indio_dev->modes = INDIO_DIRECT_MODE;
+        indio_dev->channels = ad7923_channels;
+        indio_dev->num_channels = ARRAY_SIZE(ad7923_channels);
+        indio_dev->info = &ad7923_info;
+
+        /* Setup default message */
+
+        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].rx_buf = &st->rx_buf[0];
+        st->scan_single_xfer[1].len = 2;
+
+        spi_message_init(&st->scan_single_msg);
+        spi_message_add_tail(&st->scan_single_xfer[0], &st->scan_single_msg);
+        spi_message_add_tail(&st->scan_single_xfer[1], &st->scan_single_msg);
+
+        ret = iio_triggered_buffer_setup(indio_dev, NULL,
+                        &ad7923_trigger_handler, NULL);
+        if (ret)
+                goto error_free;
+
+        ret = iio_device_register(indio_dev);
+        if (ret)
+                goto error_cleanup_ring;
+
+        return 0;
+
+error_cleanup_ring:
+        iio_triggered_buffer_cleanup(indio_dev);
+error_free:
+        iio_device_free(indio_dev);
+
+        return ret;
+}
+
+static int ad7923_remove(struct spi_device *spi)
+{
+        struct iio_dev *indio_dev = spi_get_drvdata(spi);
+
+        iio_device_unregister(indio_dev);
+        iio_triggered_buffer_cleanup(indio_dev);
+        iio_device_free(indio_dev);
+
+        return 0;
+}
+
+static const struct spi_device_id ad7923_id[] = {
+        {"ad7923", 0},
+        {}
+};
+MODULE_DEVICE_TABLE(spi, ad7923_id);
+
+static struct spi_driver ad7923_driver = {
+        .driver = {
+                .name   = "ad7923",
+                .owner  = THIS_MODULE,
+        },
+        .probe          = ad7923_probe,
+        .remove         = ad7923_remove,
+        .id_table       = ad7923_id,
+};
+module_spi_driver(ad7923_driver);
+
+MODULE_AUTHOR("Michael Hennerich <hennerich@blackfin.uclinux.org>");
+MODULE_AUTHOR("Patrick Vasseur <patrick.vasseur@c-s.fr>");
+MODULE_DESCRIPTION("Analog Devices AD7923 ADC");
+MODULE_LICENSE("GPL v2");