iio: adc: adi-axi-adc: add support for AXI ADC IP core

This change adds support for the Analog Devices Generic AXI ADC IP core.
The IP core is used for interfacing with analog-to-digital (ADC) converters
that require either a high-speed serial interface (JESD204B/C) or a source
synchronous parallel interface (LVDS/CMOS).

Usually, some other interface type (i.e SPI) is used as a control interface
for the actual ADC, while the IP core (controlled via this driver), will
interface to the data-lines of the ADC and handle the streaming of data
into memory via DMA.

Because of this, the AXI ADC driver needs the other SPI-ADC driver to
register with it. The SPI-ADC needs to be register via the SPI framework,
while the AXI ADC registers as a platform driver. The two cannot be ordered
in a hierarchy as both drivers have their own registers, and trying to
organize this [in a hierarchy becomes] problematic when trying to map
memory/registers.

There are some modes where the AXI ADC can operate as standalone ADC, but
those will be implemented at a later point in time.

DocLink: https://wiki.analog.com/resources/fpga/docs/axi_adc_ip

Signed-off-by: Michael Hennerich <[e-mail]>
Signed-off-by: Lars-Peter Clausen <[e-mail]>
Signed-off-by: Alexandru Ardelean <[e-mail]>
Signed-off-by: Jonathan Cameron <[e-mail]>

drivers/iio/adc/Kconfig

···
 	  To compile this driver as a module, choose M here: the module will be
 	  called ad799x.
 
+config ADI_AXI_ADC
+	tristate "Analog Devices Generic AXI ADC IP core driver"
+	select IIO_BUFFER
+	select IIO_BUFFER_HW_CONSUMER
+	select IIO_BUFFER_DMAENGINE
+	help
+	  Say yes here to build support for Analog Devices Generic
+	  AXI ADC IP core. The IP core is used for interfacing with
+	  analog-to-digital (ADC) converters that require either a high-speed
+	  serial interface (JESD204B/C) or a source synchronous parallel
+	  interface (LVDS/CMOS).
+	  Typically (for such devices) SPI will be used for configuration only,
+	  while this IP core handles the streaming of data into memory via DMA.
+
+	  Link: https://wiki.analog.com/resources/fpga/docs/axi_adc_ip
+	  If unsure, say N (but it's safe to say "Y").
+
+	  To compile this driver as a module, choose M here: the
+	  module will be called adi-axi-adc.
+
 config ASPEED_ADC
 	tristate "Aspeed ADC"
 	depends on ARCH_ASPEED || COMPILE_TEST

drivers/iio/adc/Makefile

···
 obj-$(CONFIG_AD7887) += ad7887.o
 obj-$(CONFIG_AD7949) += ad7949.o
 obj-$(CONFIG_AD799X) += ad799x.o
+obj-$(CONFIG_ADI_AXI_ADC) += adi-axi-adc.o
 obj-$(CONFIG_ASPEED_ADC) += aspeed_adc.o
 obj-$(CONFIG_AT91_ADC) += at91_adc.o
 obj-$(CONFIG_AT91_SAMA5D2_ADC) += at91-sama5d2_adc.o

drivers/iio/adc/adi-axi-adc.c

···
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Analog Devices Generic AXI ADC IP core
+ * Link: https://wiki.analog.com/resources/fpga/docs/axi_adc_ip
+ *
+ * Copyright 2012-2020 Analog Devices Inc.
+ */
+
+#include <linux/bitfield.h>
+#include <linux/clk.h>
+#include <linux/io.h>
+#include <linux/delay.h>
+#include <linux/module.h>
+#include <linux/of_device.h>
+#include <linux/platform_device.h>
+#include <linux/slab.h>
+
+#include <linux/iio/iio.h>
+#include <linux/iio/sysfs.h>
+#include <linux/iio/buffer.h>
+#include <linux/iio/buffer-dmaengine.h>
+
+#include <linux/fpga/adi-axi-common.h>
+#include <linux/iio/adc/adi-axi-adc.h>
+
+/**
+ * Register definitions:
+ *   https://wiki.analog.com/resources/fpga/docs/axi_adc_ip#register_map
+ */
+
+/* ADC controls */
+
+#define ADI_AXI_REG_RSTN			0x0040
+#define   ADI_AXI_REG_RSTN_CE_N			BIT(2)
+#define   ADI_AXI_REG_RSTN_MMCM_RSTN		BIT(1)
+#define   ADI_AXI_REG_RSTN_RSTN			BIT(0)
+
+/* ADC Channel controls */
+
+#define ADI_AXI_REG_CHAN_CTRL(c)		(0x0400 + (c) * 0x40)
+#define   ADI_AXI_REG_CHAN_CTRL_LB_OWR		BIT(11)
+#define   ADI_AXI_REG_CHAN_CTRL_PN_SEL_OWR	BIT(10)
+#define   ADI_AXI_REG_CHAN_CTRL_IQCOR_EN	BIT(9)
+#define   ADI_AXI_REG_CHAN_CTRL_DCFILT_EN	BIT(8)
+#define   ADI_AXI_REG_CHAN_CTRL_FMT_SIGNEXT	BIT(6)
+#define   ADI_AXI_REG_CHAN_CTRL_FMT_TYPE	BIT(5)
+#define   ADI_AXI_REG_CHAN_CTRL_FMT_EN		BIT(4)
+#define   ADI_AXI_REG_CHAN_CTRL_PN_TYPE_OWR	BIT(1)
+#define   ADI_AXI_REG_CHAN_CTRL_ENABLE		BIT(0)
+
+#define ADI_AXI_REG_CHAN_CTRL_DEFAULTS		\
+	(ADI_AXI_REG_CHAN_CTRL_FMT_SIGNEXT |	\
+	 ADI_AXI_REG_CHAN_CTRL_FMT_EN |		\
+	 ADI_AXI_REG_CHAN_CTRL_ENABLE)
+
+struct adi_axi_adc_core_info {
+	unsigned int				version;
+};
+
+struct adi_axi_adc_state {
+	struct mutex				lock;
+
+	struct adi_axi_adc_client		*client;
+	void __iomem				*regs;
+};
+
+struct adi_axi_adc_client {
+	struct list_head			entry;
+	struct adi_axi_adc_conv			conv;
+	struct adi_axi_adc_state		*state;
+	struct device				*dev;
+	const struct adi_axi_adc_core_info	*info;
+};
+
+static LIST_HEAD(registered_clients);
+static DEFINE_MUTEX(registered_clients_lock);
+
+static struct adi_axi_adc_client *conv_to_client(struct adi_axi_adc_conv *conv)
+{
+	return container_of(conv, struct adi_axi_adc_client, conv);
+}
+
+void *adi_axi_adc_conv_priv(struct adi_axi_adc_conv *conv)
+{
+	struct adi_axi_adc_client *cl = conv_to_client(conv);
+
+	return (char *)cl + ALIGN(sizeof(struct adi_axi_adc_client), IIO_ALIGN);
+}
+EXPORT_SYMBOL_GPL(adi_axi_adc_conv_priv);
+
+static void adi_axi_adc_write(struct adi_axi_adc_state *st,
+			      unsigned int reg,
+			      unsigned int val)
+{
+	iowrite32(val, st->regs + reg);
+}
+
+static unsigned int adi_axi_adc_read(struct adi_axi_adc_state *st,
+				     unsigned int reg)
+{
+	return ioread32(st->regs + reg);
+}
+
+static int adi_axi_adc_config_dma_buffer(struct device *dev,
+					 struct iio_dev *indio_dev)
+{
+	struct iio_buffer *buffer;
+	const char *dma_name;
+
+	if (!device_property_present(dev, "dmas"))
+		return 0;
+
+	if (device_property_read_string(dev, "dma-names", &dma_name))
+		dma_name = "rx";
+
+	buffer = devm_iio_dmaengine_buffer_alloc(indio_dev->dev.parent,
+						 dma_name);
+	if (IS_ERR(buffer))
+		return PTR_ERR(buffer);
+
+	indio_dev->modes |= INDIO_BUFFER_HARDWARE;
+	iio_device_attach_buffer(indio_dev, buffer);
+
+	return 0;
+}
+
+static int adi_axi_adc_read_raw(struct iio_dev *indio_dev,
+				struct iio_chan_spec const *chan,
+				int *val, int *val2, long mask)
+{
+	struct adi_axi_adc_state *st = iio_priv(indio_dev);
+	struct adi_axi_adc_conv *conv = &st->client->conv;
+
+	if (!conv->read_raw)
+		return -EOPNOTSUPP;
+
+	return conv->read_raw(conv, chan, val, val2, mask);
+}
+
+static int adi_axi_adc_write_raw(struct iio_dev *indio_dev,
+				 struct iio_chan_spec const *chan,
+				 int val, int val2, long mask)
+{
+	struct adi_axi_adc_state *st = iio_priv(indio_dev);
+	struct adi_axi_adc_conv *conv = &st->client->conv;
+
+	if (!conv->write_raw)
+		return -EOPNOTSUPP;
+
+	return conv->write_raw(conv, chan, val, val2, mask);
+}
+
+static int adi_axi_adc_update_scan_mode(struct iio_dev *indio_dev,
+					const unsigned long *scan_mask)
+{
+	struct adi_axi_adc_state *st = iio_priv(indio_dev);
+	struct adi_axi_adc_conv *conv = &st->client->conv;
+	unsigned int i, ctrl;
+
+	for (i = 0; i < conv->chip_info->num_channels; i++) {
+		ctrl = adi_axi_adc_read(st, ADI_AXI_REG_CHAN_CTRL(i));
+
+		if (test_bit(i, scan_mask))
+			ctrl |= ADI_AXI_REG_CHAN_CTRL_ENABLE;
+		else
+			ctrl &= ~ADI_AXI_REG_CHAN_CTRL_ENABLE;
+
+		adi_axi_adc_write(st, ADI_AXI_REG_CHAN_CTRL(i), ctrl);
+	}
+
+	return 0;
+}
+
+static struct adi_axi_adc_conv *adi_axi_adc_conv_register(struct device *dev,
+							  size_t sizeof_priv)
+{
+	struct adi_axi_adc_client *cl;
+	size_t alloc_size;
+
+	alloc_size = ALIGN(sizeof(struct adi_axi_adc_client), IIO_ALIGN);
+	if (sizeof_priv)
+		alloc_size += ALIGN(sizeof_priv, IIO_ALIGN);
+
+	cl = kzalloc(alloc_size, GFP_KERNEL);
+	if (!cl)
+		return ERR_PTR(-ENOMEM);
+
+	mutex_lock(&registered_clients_lock);
+
+	cl->dev = get_device(dev);
+
+	list_add_tail(&cl->entry, &registered_clients);
+
+	mutex_unlock(&registered_clients_lock);
+
+	return &cl->conv;
+}
+
+static void adi_axi_adc_conv_unregister(struct adi_axi_adc_conv *conv)
+{
+	struct adi_axi_adc_client *cl = conv_to_client(conv);
+
+	mutex_lock(&registered_clients_lock);
+
+	list_del(&cl->entry);
+	put_device(cl->dev);
+
+	mutex_unlock(&registered_clients_lock);
+
+	kfree(cl);
+}
+
+static void devm_adi_axi_adc_conv_release(struct device *dev, void *res)
+{
+	adi_axi_adc_conv_unregister(*(struct adi_axi_adc_conv **)res);
+}
+
+struct adi_axi_adc_conv *devm_adi_axi_adc_conv_register(struct device *dev,
+							size_t sizeof_priv)
+{
+	struct adi_axi_adc_conv **ptr, *conv;
+
+	ptr = devres_alloc(devm_adi_axi_adc_conv_release, sizeof(*ptr),
+			   GFP_KERNEL);
+	if (!ptr)
+		return ERR_PTR(-ENOMEM);
+
+	conv = adi_axi_adc_conv_register(dev, sizeof_priv);
+	if (IS_ERR(conv)) {
+		devres_free(ptr);
+		return ERR_CAST(conv);
+	}
+
+	*ptr = conv;
+	devres_add(dev, ptr);
+
+	return conv;
+}
+EXPORT_SYMBOL_GPL(devm_adi_axi_adc_conv_register);
+
+static ssize_t in_voltage_scale_available_show(struct device *dev,
+					       struct device_attribute *attr,
+					       char *buf)
+{
+	struct iio_dev *indio_dev = dev_to_iio_dev(dev);
+	struct adi_axi_adc_state *st = iio_priv(indio_dev);
+	struct adi_axi_adc_conv *conv = &st->client->conv;
+	size_t len = 0;
+	int i;
+
+	for (i = 0; i < conv->chip_info->num_scales; i++) {
+		const unsigned int *s = conv->chip_info->scale_table[i];
+
+		len += scnprintf(buf + len, PAGE_SIZE - len,
+				 "%u.%06u ", s[0], s[1]);
+	}
+	buf[len - 1] = '\n';
+
+	return len;
+}
+
+static IIO_DEVICE_ATTR_RO(in_voltage_scale_available, 0);
+
+enum {
+	ADI_AXI_ATTR_SCALE_AVAIL,
+};
+
+#define ADI_AXI_ATTR(_en_, _file_)			\
+	[ADI_AXI_ATTR_##_en_] = &iio_dev_attr_##_file_.dev_attr.attr
+
+static struct attribute *adi_axi_adc_attributes[] = {
+	ADI_AXI_ATTR(SCALE_AVAIL, in_voltage_scale_available),
+	NULL
+};
+
+static umode_t axi_adc_attr_is_visible(struct kobject *kobj,
+				       struct attribute *attr, int n)
+{
+	struct device *dev = container_of(kobj, struct device, kobj);
+	struct iio_dev *indio_dev = dev_to_iio_dev(dev);
+	struct adi_axi_adc_state *st = iio_priv(indio_dev);
+	struct adi_axi_adc_conv *conv = &st->client->conv;
+
+	switch (n) {
+	case ADI_AXI_ATTR_SCALE_AVAIL:
+		if (!conv->chip_info->num_scales)
+			return 0;
+		return attr->mode;
+	default:
+		return attr->mode;
+	}
+}
+
+static const struct attribute_group adi_axi_adc_attribute_group = {
+	.attrs = adi_axi_adc_attributes,
+	.is_visible = axi_adc_attr_is_visible,
+};
+
+static const struct iio_info adi_axi_adc_info = {
+	.read_raw = &adi_axi_adc_read_raw,
+	.write_raw = &adi_axi_adc_write_raw,
+	.attrs = &adi_axi_adc_attribute_group,
+	.update_scan_mode = &adi_axi_adc_update_scan_mode,
+};
+
+static const struct adi_axi_adc_core_info adi_axi_adc_10_0_a_info = {
+	.version = ADI_AXI_PCORE_VER(10, 0, 'a'),
+};
+
+static struct adi_axi_adc_client *adi_axi_adc_attach_client(struct device *dev)
+{
+	const struct adi_axi_adc_core_info *info;
+	struct adi_axi_adc_client *cl;
+	struct device_node *cln;
+
+	info = of_device_get_match_data(dev);
+	if (!info)
+		return ERR_PTR(-ENODEV);
+
+	cln = of_parse_phandle(dev->of_node, "adi,adc-dev", 0);
+	if (!cln) {
+		dev_err(dev, "No 'adi,adc-dev' node defined\n");
+		return ERR_PTR(-ENODEV);
+	}
+
+	mutex_lock(&registered_clients_lock);
+
+	list_for_each_entry(cl, &registered_clients, entry) {
+		if (!cl->dev)
+			continue;
+
+		if (cl->dev->of_node != cln)
+			continue;
+
+		if (!try_module_get(dev->driver->owner)) {
+			mutex_unlock(&registered_clients_lock);
+			return ERR_PTR(-ENODEV);
+		}
+
+		get_device(dev);
+		cl->info = info;
+		mutex_unlock(&registered_clients_lock);
+		return cl;
+	}
+
+	mutex_unlock(&registered_clients_lock);
+
+	return ERR_PTR(-EPROBE_DEFER);
+}
+
+static int adi_axi_adc_setup_channels(struct device *dev,
+				      struct adi_axi_adc_state *st)
+{
+	struct adi_axi_adc_conv *conv = &st->client->conv;
+	int i, ret;
+
+	if (conv->preenable_setup) {
+		ret = conv->preenable_setup(conv);
+		if (ret)
+			return ret;
+	}
+
+	for (i = 0; i < conv->chip_info->num_channels; i++) {
+		adi_axi_adc_write(st, ADI_AXI_REG_CHAN_CTRL(i),
+				  ADI_AXI_REG_CHAN_CTRL_DEFAULTS);
+	}
+
+	return 0;
+}
+
+static void axi_adc_reset(struct adi_axi_adc_state *st)
+{
+	adi_axi_adc_write(st, ADI_AXI_REG_RSTN, 0);
+	mdelay(10);
+	adi_axi_adc_write(st, ADI_AXI_REG_RSTN, ADI_AXI_REG_RSTN_MMCM_RSTN);
+	mdelay(10);
+	adi_axi_adc_write(st, ADI_AXI_REG_RSTN,
+			  ADI_AXI_REG_RSTN_RSTN | ADI_AXI_REG_RSTN_MMCM_RSTN);
+}
+
+static void adi_axi_adc_cleanup(void *data)
+{
+	struct adi_axi_adc_client *cl = data;
+
+	put_device(cl->dev);
+	module_put(cl->dev->driver->owner);
+}
+
+static int adi_axi_adc_probe(struct platform_device *pdev)
+{
+	struct adi_axi_adc_conv *conv;
+	struct iio_dev *indio_dev;
+	struct adi_axi_adc_client *cl;
+	struct adi_axi_adc_state *st;
+	unsigned int ver;
+	int ret;
+
+	cl = adi_axi_adc_attach_client(&pdev->dev);
+	if (IS_ERR(cl))
+		return PTR_ERR(cl);
+
+	ret = devm_add_action_or_reset(&pdev->dev, adi_axi_adc_cleanup, cl);
+	if (ret)
+		return ret;
+
+	indio_dev = devm_iio_device_alloc(&pdev->dev, sizeof(*st));
+	if (indio_dev == NULL)
+		return -ENOMEM;
+
+	st = iio_priv(indio_dev);
+	st->client = cl;
+	cl->state = st;
+	mutex_init(&st->lock);
+
+	st->regs = devm_platform_ioremap_resource(pdev, 0);
+	if (IS_ERR(st->regs))
+		return PTR_ERR(st->regs);
+
+	conv = &st->client->conv;
+
+	axi_adc_reset(st);
+
+	ver = adi_axi_adc_read(st, ADI_AXI_REG_VERSION);
+
+	if (cl->info->version > ver) {
+		dev_err(&pdev->dev,
+			"IP core version is too old. Expected %d.%.2d.%c, Reported %d.%.2d.%c\n",
+			ADI_AXI_PCORE_VER_MAJOR(cl->info->version),
+			ADI_AXI_PCORE_VER_MINOR(cl->info->version),
+			ADI_AXI_PCORE_VER_PATCH(cl->info->version),
+			ADI_AXI_PCORE_VER_MAJOR(ver),
+			ADI_AXI_PCORE_VER_MINOR(ver),
+			ADI_AXI_PCORE_VER_PATCH(ver));
+		return -ENODEV;
+	}
+
+	indio_dev->info = &adi_axi_adc_info;
+	indio_dev->dev.parent = &pdev->dev;
+	indio_dev->name = "adi-axi-adc";
+	indio_dev->modes = INDIO_DIRECT_MODE;
+	indio_dev->num_channels = conv->chip_info->num_channels;
+	indio_dev->channels = conv->chip_info->channels;
+
+	ret = adi_axi_adc_config_dma_buffer(&pdev->dev, indio_dev);
+	if (ret)
+		return ret;
+
+	ret = adi_axi_adc_setup_channels(&pdev->dev, st);
+	if (ret)
+		return ret;
+
+	ret = devm_iio_device_register(&pdev->dev, indio_dev);
+	if (ret)
+		return ret;
+
+	dev_info(&pdev->dev, "AXI ADC IP core (%d.%.2d.%c) probed\n",
+		 ADI_AXI_PCORE_VER_MAJOR(ver),
+		 ADI_AXI_PCORE_VER_MINOR(ver),
+		 ADI_AXI_PCORE_VER_PATCH(ver));
+
+	return 0;
+}
+
+/* Match table for of_platform binding */
+static const struct of_device_id adi_axi_adc_of_match[] = {
+	{ .compatible = "adi,axi-adc-10.0.a", .data = &adi_axi_adc_10_0_a_info },
+	{ /* end of list */ }
+};
+MODULE_DEVICE_TABLE(of, adi_axi_adc_of_match);
+
+static struct platform_driver adi_axi_adc_driver = {
+	.driver = {
+		.name = KBUILD_MODNAME,
+		.of_match_table = adi_axi_adc_of_match,
+	},
+	.probe = adi_axi_adc_probe,
+};
+module_platform_driver(adi_axi_adc_driver);
+
+MODULE_AUTHOR("Michael Hennerich <[e-mail]>");
+MODULE_DESCRIPTION("Analog Devices Generic AXI ADC IP core driver");
+MODULE_LICENSE("GPL v2");

include/linux/iio/adc/adi-axi-adc.h

···
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Analog Devices Generic AXI ADC IP core driver/library
+ * Link: https://wiki.analog.com/resources/fpga/docs/axi_adc_ip
+ *
+ * Copyright 2012-2020 Analog Devices Inc.
+ */
+#ifndef __ADI_AXI_ADC_H__
+#define __ADI_AXI_ADC_H__
+
+struct device;
+struct iio_chan_spec;
+
+/**
+ * struct adi_axi_adc_chip_info - Chip specific information
+ * @name		Chip name
+ * @id			Chip ID (usually product ID)
+ * @channels		Channel specifications of type @struct axi_adc_chan_spec
+ * @num_channels	Number of @channels
+ * @scale_table		Supported scales by the chip; tuples of 2 ints
+ * @num_scales		Number of scales in the table
+ * @max_rate		Maximum sampling rate supported by the device
+ */
+struct adi_axi_adc_chip_info {
+	const char			*name;
+	unsigned int			id;
+
+	const struct iio_chan_spec	*channels;
+	unsigned int			num_channels;
+
+	const unsigned int		(*scale_table)[2];
+	int				num_scales;
+
+	unsigned long			max_rate;
+};
+
+/**
+ * struct adi_axi_adc_conv - data of the ADC attached to the AXI ADC
+ * @chip_info		chip info details for the client ADC
+ * @preenable_setup	op to run in the client before enabling the AXI ADC
+ * @reg_access		IIO debugfs_reg_access hook for the client ADC
+ * @read_raw		IIO read_raw hook for the client ADC
+ * @write_raw		IIO write_raw hook for the client ADC
+ */
+struct adi_axi_adc_conv {
+	const struct adi_axi_adc_chip_info		*chip_info;
+
+	int (*preenable_setup)(struct adi_axi_adc_conv *conv);
+	int (*reg_access)(struct adi_axi_adc_conv *conv, unsigned int reg,
+			  unsigned int writeval, unsigned int *readval);
+	int (*read_raw)(struct adi_axi_adc_conv *conv,
+			struct iio_chan_spec const *chan,
+			int *val, int *val2, long mask);
+	int (*write_raw)(struct adi_axi_adc_conv *conv,
+			 struct iio_chan_spec const *chan,
+			 int val, int val2, long mask);
+};
+
+struct adi_axi_adc_conv *devm_adi_axi_adc_conv_register(struct device *dev,
+							size_t sizeof_priv);
+
+void *adi_axi_adc_conv_priv(struct adi_axi_adc_conv *conv);
+
+#endif