IIO: ADC: New driver for the AD7298 8-channel SPI ADC

This patch adds support for the
AD7298:  8-Channel, 1MSPS, 12-Bit SAR ADC with Temperature Sensor
via SPI bus.

This patch replaces the existing ad7298.c driver completely.
It was necessary since, the old driver did not comply with the
IIO ABI for such devices.

Changes since V1:
IIO: ADC: New driver for the AD7298 8-channel SPI ADC

Add documentation for new sysfs file tempX_input.
Simplify bit defines.
Remove outdated comments.
Fix indention style.
ad7298_show_temp():
	Add locking.
	Simplify temperature calculation.
	Change temperature result from degrees into milli degrees Celsius.
	Rename file according to new sysfs ABI documentation

Add timestamp attributes.
Revise timestamp handling accordingly.
Preset timestamp generation.

Signed-off-by: Michael Hennerich <michael.hennerich@analog.com>
Acked-by: Jonathan Cameron <jic23@cam.ac.uk>
Reviewed-by: Shubhrajyoti <Shubhrajyoti@ti.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

1 files changed, 258 insertions, 0 deletions

diff --git a/drivers/staging/iio/adc/ad7298_ring.c b/drivers/staging/iio/adc/ad7298_ring.c
new file mode 100644
index 000000000000..19d1aced1e6c
--- /dev/null
+++ b/drivers/staging/iio/adc/ad7298_ring.c
@@ -0,0 +1,258 @@
+/*
+ * AD7298 SPI ADC driver
+ *
+ * Copyright 2011 Analog Devices Inc.
+ *
+ * Licensed under the GPL-2.
+ */
+
+#include <linux/interrupt.h>
+#include <linux/workqueue.h>
+#include <linux/device.h>
+#include <linux/kernel.h>
+#include <linux/slab.h>
+#include <linux/sysfs.h>
+#include <linux/spi/spi.h>
+
+#include "../iio.h"
+#include "../ring_generic.h"
+#include "../ring_sw.h"
+#include "../trigger.h"
+#include "../sysfs.h"
+
+#include "ad7298.h"
+
+static IIO_SCAN_EL_C(in0, 0, 0, NULL);
+static IIO_SCAN_EL_C(in1, 1, 0, NULL);
+static IIO_SCAN_EL_C(in2, 2, 0, NULL);
+static IIO_SCAN_EL_C(in3, 3, 0, NULL);
+static IIO_SCAN_EL_C(in4, 4, 0, NULL);
+static IIO_SCAN_EL_C(in5, 5, 0, NULL);
+static IIO_SCAN_EL_C(in6, 6, 0, NULL);
+static IIO_SCAN_EL_C(in7, 7, 0, NULL);
+
+static IIO_SCAN_EL_TIMESTAMP(8);
+static IIO_CONST_ATTR_SCAN_EL_TYPE(timestamp, s, 64, 64);
+
+static IIO_CONST_ATTR(in_type, "u12/16") ;
+
+static struct attribute *ad7298_scan_el_attrs[] = {
+	&iio_scan_el_in0.dev_attr.attr,
+	&iio_const_attr_in0_index.dev_attr.attr,
+	&iio_scan_el_in1.dev_attr.attr,
+	&iio_const_attr_in1_index.dev_attr.attr,
+	&iio_scan_el_in2.dev_attr.attr,
+	&iio_const_attr_in2_index.dev_attr.attr,
+	&iio_scan_el_in3.dev_attr.attr,
+	&iio_const_attr_in3_index.dev_attr.attr,
+	&iio_scan_el_in4.dev_attr.attr,
+	&iio_const_attr_in4_index.dev_attr.attr,
+	&iio_scan_el_in5.dev_attr.attr,
+	&iio_const_attr_in5_index.dev_attr.attr,
+	&iio_scan_el_in6.dev_attr.attr,
+	&iio_const_attr_in6_index.dev_attr.attr,
+	&iio_scan_el_in7.dev_attr.attr,
+	&iio_const_attr_in7_index.dev_attr.attr,
+	&iio_const_attr_timestamp_index.dev_attr.attr,
+	&iio_scan_el_timestamp.dev_attr.attr,
+	&iio_const_attr_timestamp_type.dev_attr.attr,
+	&iio_const_attr_in_type.dev_attr.attr,
+	NULL,
+};
+
+static struct attribute_group ad7298_scan_el_group = {
+	.name = "scan_elements",
+	.attrs = ad7298_scan_el_attrs,
+};
+
+int ad7298_scan_from_ring(struct ad7298_state *st, long ch)
+{
+	struct iio_ring_buffer *ring = st->indio_dev->ring;
+	int ret;
+	u16 *ring_data;
+
+	if (!(ring->scan_mask & (1 << ch))) {
+		ret = -EBUSY;
+		goto error_ret;
+	}
+
+	ring_data = kmalloc(ring->access.get_bytes_per_datum(ring), GFP_KERNEL);
+	if (ring_data == NULL) {
+		ret = -ENOMEM;
+		goto error_ret;
+	}
+	ret = ring->access.read_last(ring, (u8 *) ring_data);
+	if (ret)
+		goto error_free_ring_data;
+
+	ret = be16_to_cpu(ring_data[ch]);
+
+error_free_ring_data:
+	kfree(ring_data);
+error_ret:
+	return ret;
+}
+
+/**
+ * ad7298_ring_preenable() setup the parameters of the ring before enabling
+ *
+ * The complex nature of the setting of the number of bytes per datum is due
+ * to this driver currently ensuring that the timestamp is stored at an 8
+ * byte boundary.
+ **/
+static int ad7298_ring_preenable(struct iio_dev *indio_dev)
+{
+	struct ad7298_state *st = indio_dev->dev_data;
+	struct iio_ring_buffer *ring = indio_dev->ring;
+	size_t d_size;
+	int i, m;
+	unsigned short command;
+
+	d_size = ring->scan_count * (AD7298_STORAGE_BITS / 8);
+
+	if (ring->scan_timestamp) {
+		d_size += sizeof(s64);
+
+		if (d_size % sizeof(s64))
+			d_size += sizeof(s64) - (d_size % sizeof(s64));
+	}
+
+	if (ring->access.set_bytes_per_datum)
+		ring->access.set_bytes_per_datum(ring, d_size);
+
+	st->d_size = d_size;
+
+	command = AD7298_WRITE | st->ext_ref;
+
+	for (i = 0, m = AD7298_CH(0); i < AD7298_MAX_CHAN; i++, m >>= 1)
+		if (ring->scan_mask & (1 << i))
+			command |= m;
+
+	st->tx_buf[0] = cpu_to_be16(command);
+
+	/* build spi ring message */
+	st->ring_xfer[0].tx_buf = &st->tx_buf[0];
+	st->ring_xfer[0].len = 2;
+	st->ring_xfer[0].cs_change = 1;
+	st->ring_xfer[1].tx_buf = &st->tx_buf[1];
+	st->ring_xfer[1].len = 2;
+	st->ring_xfer[1].cs_change = 1;
+
+	spi_message_init(&st->ring_msg);
+	spi_message_add_tail(&st->ring_xfer[0], &st->ring_msg);
+	spi_message_add_tail(&st->ring_xfer[1], &st->ring_msg);
+
+	for (i = 0; i < ring->scan_count; i++) {
+		st->ring_xfer[i + 2].rx_buf = &st->rx_buf[i];
+		st->ring_xfer[i + 2].len = 2;
+		st->ring_xfer[i + 2].cs_change = 1;
+		spi_message_add_tail(&st->ring_xfer[i + 2], &st->ring_msg);
+	}
+	/* make sure last transfer cs_change is not set */
+	st->ring_xfer[i + 1].cs_change = 0;
+
+	return 0;
+}
+
+/**
+ * ad7298_poll_func_th() th of trigger launched polling to ring buffer
+ *
+ * As sampling only occurs on spi comms occuring, leave timestamping until
+ * then.  Some triggers will generate their own time stamp.  Currently
+ * there is no way of notifying them when no one cares.
+ **/
+static void ad7298_poll_func_th(struct iio_dev *indio_dev, s64 time)
+{
+	struct ad7298_state *st = indio_dev->dev_data;
+
+	schedule_work(&st->poll_work);
+	return;
+}
+
+/**
+ * ad7298_poll_bh_to_ring() bh of trigger launched polling to ring buffer
+ * @work_s:	the work struct through which this was scheduled
+ *
+ * Currently there is no option in this driver to disable the saving of
+ * timestamps within the ring.
+ * I think the one copy of this at a time was to avoid problems if the
+ * trigger was set far too high and the reads then locked up the computer.
+ **/
+static void ad7298_poll_bh_to_ring(struct work_struct *work_s)
+{
+	struct ad7298_state *st = container_of(work_s, struct ad7298_state,
+						  poll_work);
+	struct iio_dev *indio_dev = st->indio_dev;
+	struct iio_sw_ring_buffer *sw_ring = iio_to_sw_ring(indio_dev->ring);
+	struct iio_ring_buffer *ring = indio_dev->ring;
+	s64 time_ns;
+	__u16 buf[16];
+	int b_sent, i;
+
+	/* Ensure only one copy of this function running at a time */
+	if (atomic_inc_return(&st->protect_ring) > 1)
+		return;
+
+	b_sent = spi_sync(st->spi, &st->ring_msg);
+	if (b_sent)
+		goto done;
+
+	if (ring->scan_timestamp) {
+		time_ns = iio_get_time_ns();
+		memcpy((u8 *)buf + st->d_size - sizeof(s64),
+			&time_ns, sizeof(time_ns));
+	}
+
+	for (i = 0; i < ring->scan_count; i++)
+		buf[i] = be16_to_cpu(st->rx_buf[i]);
+
+	indio_dev->ring->access.store_to(&sw_ring->buf, (u8 *)buf, time_ns);
+done:
+	atomic_dec(&st->protect_ring);
+}
+
+int ad7298_register_ring_funcs_and_init(struct iio_dev *indio_dev)
+{
+	struct ad7298_state *st = indio_dev->dev_data;
+	int ret;
+
+	indio_dev->ring = iio_sw_rb_allocate(indio_dev);
+	if (!indio_dev->ring) {
+		ret = -ENOMEM;
+		goto error_ret;
+	}
+	/* Effectively select the ring buffer implementation */
+	iio_ring_sw_register_funcs(&indio_dev->ring->access);
+	ret = iio_alloc_pollfunc(indio_dev, NULL, &ad7298_poll_func_th);
+	if (ret)
+		goto error_deallocate_sw_rb;
+
+	/* Ring buffer functions - here trigger setup related */
+
+	indio_dev->ring->preenable = &ad7298_ring_preenable;
+	indio_dev->ring->postenable = &iio_triggered_ring_postenable;
+	indio_dev->ring->predisable = &iio_triggered_ring_predisable;
+	indio_dev->ring->scan_el_attrs = &ad7298_scan_el_group;
+	indio_dev->ring->scan_timestamp = true;
+
+	INIT_WORK(&st->poll_work, &ad7298_poll_bh_to_ring);
+
+	/* Flag that polled ring buffering is possible */
+	indio_dev->modes |= INDIO_RING_TRIGGERED;
+	return 0;
+error_deallocate_sw_rb:
+	iio_sw_rb_free(indio_dev->ring);
+error_ret:
+	return ret;
+}
+
+void ad7298_ring_cleanup(struct iio_dev *indio_dev)
+{
+	if (indio_dev->trig) {
+		iio_put_trigger(indio_dev->trig);
+		iio_trigger_dettach_poll_func(indio_dev->trig,
+					      indio_dev->pollfunc);
+	}
+	kfree(indio_dev->pollfunc);
+	iio_sw_rb_free(indio_dev->ring);
+}