iio: amplifiers: New driver for AD8366 Dual-Digital Variable Gain Amplifier

Changes since V1:

Apply review feedback:
	Introduce and use IIO_CHAN_INFO_HARDWAREGAIN
	Introduce and use Use IIO_VAL_INT_PLUS_MICRO_DB

Modify out of staging include paths.
Convert to new iio core API naming.

Changes since V2:

more sanity checking in write_raw

Signed-off-by: Michael Hennerich <michael.hennerich@analog.com>
Acked-by: Jonathan Cameron <jic23@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

5 files changed, 248 insertions, 0 deletions

diff --git a/drivers/iio/Kconfig b/drivers/iio/Kconfig
index 3ab7d48d0b0a..bb1e35c811da 100644
--- a/drivers/iio/Kconfig
+++ b/drivers/iio/Kconfig
@@ -48,4 +48,6 @@ config IIO_CONSUMERS_PER_TRIGGER
         This value controls the maximum number of consumers that a
         given trigger may handle. Default is 2.
 
+source "drivers/iio/amplifiers/Kconfig"
+
 endif # IIO
diff --git a/drivers/iio/Makefile b/drivers/iio/Makefile
index d5fc57d12eac..55524916aa56 100644
--- a/drivers/iio/Makefile
+++ b/drivers/iio/Makefile
@@ -8,3 +8,5 @@ industrialio-$(CONFIG_IIO_BUFFER) += industrialio-buffer.o
 industrialio-$(CONFIG_IIO_TRIGGER) += industrialio-trigger.o
 
 obj-$(CONFIG_IIO_KFIFO_BUF) += kfifo_buf.o
+
+obj-y += amplifiers/
diff --git a/drivers/iio/amplifiers/Kconfig b/drivers/iio/amplifiers/Kconfig
new file mode 100644
index 000000000000..05d707ed7d4f
--- /dev/null
+++ b/drivers/iio/amplifiers/Kconfig
@@ -0,0 +1,17 @@
+#
+# Gain Amplifiers, etc.
+#
+menu "Amplifiers"
+
+config AD8366
+        tristate "Analog Devices AD8366 VGA"
+        depends on SPI
+        select BITREVERSE
+        help
+          Say yes here to build support for Analog Devices AD8366
+          SPI Dual-Digital Variable Gain Amplifier (VGA).
+
+          To compile this driver as a module, choose M here: the
+          module will be called ad8366.
+
+endmenu
diff --git a/drivers/iio/amplifiers/Makefile b/drivers/iio/amplifiers/Makefile
new file mode 100644
index 000000000000..a6ca366908e0
--- /dev/null
+++ b/drivers/iio/amplifiers/Makefile
@@ -0,0 +1,5 @@
+#
+# Makefile iio/amplifiers
+#
+
+obj-$(CONFIG_AD8366) += ad8366.o
diff --git a/drivers/iio/amplifiers/ad8366.c b/drivers/iio/amplifiers/ad8366.c
new file mode 100644
index 000000000000..d8281cdbfc4a
--- /dev/null
+++ b/drivers/iio/amplifiers/ad8366.c
@@ -0,0 +1,222 @@
+/*
+ * AD8366 SPI Dual-Digital Variable Gain Amplifier (VGA)
+ *
+ * Copyright 2012 Analog Devices Inc.
+ *
+ * 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/regulator/consumer.h>
+#include <linux/err.h>
+#include <linux/module.h>
+#include <linux/bitrev.h>
+
+#include <linux/iio/iio.h>
+#include <linux/iio/sysfs.h>
+
+struct ad8366_state {
+        struct spi_device       *spi;
+        struct regulator        *reg;
+        unsigned char           ch[2];
+        /*
+         * DMA (thus cache coherency maintenance) requires the
+         * transfer buffers to live in their own cache lines.
+         */
+        unsigned char           data[2] ____cacheline_aligned;
+};
+
+static int ad8366_write(struct iio_dev *indio_dev,
+                        unsigned char ch_a, char unsigned ch_b)
+{
+        struct ad8366_state *st = iio_priv(indio_dev);
+        int ret;
+
+        ch_a = bitrev8(ch_a & 0x3F);
+        ch_b = bitrev8(ch_b & 0x3F);
+
+        st->data[0] = ch_b >> 4;
+        st->data[1] = (ch_b << 4) | (ch_a >> 2);
+
+        ret = spi_write(st->spi, st->data, ARRAY_SIZE(st->data));
+        if (ret < 0)
+                dev_err(&indio_dev->dev, "write failed (%d)", ret);
+
+        return ret;
+}
+
+static int ad8366_read_raw(struct iio_dev *indio_dev,
+                           struct iio_chan_spec const *chan,
+                           int *val,
+                           int *val2,
+                           long m)
+{
+        struct ad8366_state *st = iio_priv(indio_dev);
+        int ret;
+        unsigned code;
+
+        mutex_lock(&indio_dev->mlock);
+        switch (m) {
+        case IIO_CHAN_INFO_HARDWAREGAIN:
+                code = st->ch[chan->channel];
+
+                /* Values in dB */
+                code = code * 253 + 4500;
+                *val = code / 1000;
+                *val2 = (code % 1000) * 1000;
+
+                ret = IIO_VAL_INT_PLUS_MICRO_DB;
+                break;
+        default:
+                ret = -EINVAL;
+        }
+        mutex_unlock(&indio_dev->mlock);
+
+        return ret;
+};
+
+static int ad8366_write_raw(struct iio_dev *indio_dev,
+                            struct iio_chan_spec const *chan,
+                            int val,
+                            int val2,
+                            long mask)
+{
+        struct ad8366_state *st = iio_priv(indio_dev);
+        unsigned code;
+        int ret;
+
+        if (val < 0 || val2 < 0)
+                return -EINVAL;
+
+        /* Values in dB */
+        code = (((u8)val * 1000) + ((u32)val2 / 1000));
+
+        if (code > 20500 || code < 4500)
+                return -EINVAL;
+
+        code = (code - 4500) / 253;
+
+        mutex_lock(&indio_dev->mlock);
+        switch (mask) {
+        case IIO_CHAN_INFO_HARDWAREGAIN:
+                st->ch[chan->channel] = code;
+                ret = ad8366_write(indio_dev, st->ch[0], st->ch[1]);
+                break;
+        default:
+                ret = -EINVAL;
+        }
+        mutex_unlock(&indio_dev->mlock);
+
+        return ret;
+}
+
+static const struct iio_info ad8366_info = {
+        .read_raw = &ad8366_read_raw,
+        .write_raw = &ad8366_write_raw,
+        .driver_module = THIS_MODULE,
+};
+
+#define AD8366_CHAN(_channel) {                         \
+        .type = IIO_VOLTAGE,                            \
+        .output = 1,                                    \
+        .indexed = 1,                                   \
+        .channel = _channel,                            \
+        .info_mask = IIO_CHAN_INFO_HARDWAREGAIN_SEPARATE_BIT,\
+}
+
+static const struct iio_chan_spec ad8366_channels[] = {
+        AD8366_CHAN(0),
+        AD8366_CHAN(1),
+};
+
+static int __devinit ad8366_probe(struct spi_device *spi)
+{
+        struct iio_dev *indio_dev;
+        struct ad8366_state *st;
+        int ret;
+
+        indio_dev = iio_device_alloc(sizeof(*st));
+        if (indio_dev == NULL)
+                return -ENOMEM;
+
+        st = iio_priv(indio_dev);
+
+        st->reg = regulator_get(&spi->dev, "vcc");
+        if (!IS_ERR(st->reg)) {
+                ret = regulator_enable(st->reg);
+                if (ret)
+                        goto error_put_reg;
+        }
+
+        spi_set_drvdata(spi, indio_dev);
+        st->spi = spi;
+
+        indio_dev->dev.parent = &spi->dev;
+        indio_dev->name = spi_get_device_id(spi)->name;
+        indio_dev->info = &ad8366_info;
+        i