From: Angelo Dureghello <adureghello@baylibre.com>

Add High Speed ad3552r platform driver.

The ad3552r DAC is controlled by a custom (fpga-based) DAC IP
through the current AXI backend, or similar alternative IIO backend.

Compared to the existing driver (ad3552r.c), that is a simple SPI
driver, this driver is coupled with a DAC IIO backend that finally
controls the ad3552r by a fpga-based "QSPI+DDR" interface, to reach
maximum transfer rate of 33MUPS using dma stream capabilities.

All commands involving QSPI bus read/write are delegated to the backend
through the provided APIs for bus read/write.

Signed-off-by: Angelo Dureghello <adureghello@baylibre.com>
---
 drivers/iio/dac/Kconfig                  |  14 +
 drivers/iio/dac/Makefile                 |   1 +
 drivers/iio/dac/ad3552r-hs.c             | 526 +++++++++++++++++++++++++++++++
 drivers/iio/dac/ad3552r.h                |   7 +
 include/linux/platform_data/ad3552r-hs.h |  18 ++
 5 files changed, 566 insertions(+)

diff --git a/drivers/iio/dac/Kconfig b/drivers/iio/dac/Kconfig
index fa091995d002..fc11698e88f2 100644
--- a/drivers/iio/dac/Kconfig
+++ b/drivers/iio/dac/Kconfig
@@ -6,6 +6,20 @@
 
 menu "Digital to analog converters"
 
+config AD3552R_HS
+	tristate "Analog Devices AD3552R DAC High Speed driver"
+	select ADI_AXI_DAC
+	help
+	  Say yes here to build support for Analog Devices AD3552R
+	  Digital to Analog Converter High Speed driver.
+
+          The driver requires the assistance of an IP core to operate,
+          since data is streamed into target device via DMA, sent over a
+	  QSPI + DDR (Double Data Rate) bus.
+
+	  To compile this driver as a module, choose M here: the
+	  module will be called ad3552r-hs.
+
 config AD3552R
 	tristate "Analog Devices AD3552R DAC driver"
 	depends on SPI_MASTER
diff --git a/drivers/iio/dac/Makefile b/drivers/iio/dac/Makefile
index c92de0366238..d92e08ca93ca 100644
--- a/drivers/iio/dac/Makefile
+++ b/drivers/iio/dac/Makefile
@@ -4,6 +4,7 @@
 #
 
 # When adding new entries keep the list in alphabetical order
+obj-$(CONFIG_AD3552R_HS) += ad3552r-hs.o ad3552r-common.o
 obj-$(CONFIG_AD3552R) += ad3552r.o ad3552r-common.o
 obj-$(CONFIG_AD5360) += ad5360.o
 obj-$(CONFIG_AD5380) += ad5380.o
diff --git a/drivers/iio/dac/ad3552r-hs.c b/drivers/iio/dac/ad3552r-hs.c
new file mode 100644
index 000000000000..4de33988721f
--- /dev/null
+++ b/drivers/iio/dac/ad3552r-hs.c
@@ -0,0 +1,526 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Analog Devices AD3552R
+ * Digital to Analog converter driver, High Speed version
+ *
+ * Copyright 2024 Analog Devices Inc.
+ */
+
+#include <linux/bitfield.h>
+#include <linux/delay.h>
+#include <linux/gpio/consumer.h>
+#include <linux/iio/backend.h>
+#include <linux/iio/buffer.h>
+#include <linux/mod_devicetable.h>
+#include <linux/platform_data/ad3552r-hs.h>
+#include <linux/platform_device.h>
+#include <linux/property.h>
+#include <linux/units.h>
+
+#include "ad3552r.h"
+
+struct ad3552r_hs_state {
+	const struct ad3552r_model_data *model_data;
+	struct gpio_desc *reset_gpio;
+	struct device *dev;
+	struct iio_backend *back;
+	bool single_channel;
+	struct ad3552r_hs_platform_data *data;
+	bool ddr_mode;
+};
+
+static int ad3552r_qspi_update_reg_bits(struct ad3552r_hs_state *st,
+					u32 reg, u32 mask, u32 val,
+					size_t xfer_size)
+{
+	u32 rval;
+	int err;
+
+	err = st->data->bus_reg_read(st->back, reg, &rval, xfer_size);
+	if (err)
+		return err;
+
+	rval &= ~mask;
+	rval |= val;
+
+	return st->data->bus_reg_write(st->back, reg, rval, xfer_size);
+}
+
+static int ad3552r_hs_read_raw(struct iio_dev *indio_dev,
+			       struct iio_chan_spec const *chan,
+			       int *val, int *val2, long mask)
+{
+	struct ad3552r_hs_state *st = iio_priv(indio_dev);
+	int ret;
+
+	switch (mask) {
+	case IIO_CHAN_INFO_SAMP_FREQ: {
+		int sclk;
+
+		ret = iio_backend_read_raw(st->back, chan, &sclk, 0,
+					   IIO_CHAN_INFO_FREQUENCY);
+		if (ret != IIO_VAL_INT)
+			return -EINVAL;
+
+		/* Using 4 lanes (QSPI) */
+		*val = DIV_ROUND_CLOSEST(sclk * 4 * (1 + st->ddr_mode),
+					 chan->scan_type.storagebits);
+
+		return IIO_VAL_INT;
+	}
+	case IIO_CHAN_INFO_RAW:
+		ret = st->data->bus_reg_read(st->back,
+				AD3552R_REG_ADDR_CH_DAC_16B(chan->channel),
+				val, 2);
+		if (ret)
+			return ret;
+
+		return IIO_VAL_INT;
+	default:
+		return -EINVAL;
+	}
+}
+
+static int ad3552r_hs_write_raw(struct iio_dev *indio_dev,
+				struct iio_chan_spec const *chan,
+				int val, int val2, long mask)
+{
+	struct ad3552r_hs_state *st = iio_priv(indio_dev);
+
+	switch (mask) {
+	case IIO_CHAN_INFO_RAW:
+		iio_device_claim_direct_scoped(return -EBUSY, indio_dev) {
+			return st->data->bus_reg_write(st->back,
+				    AD3552R_REG_ADDR_CH_DAC_16B(chan->channel),
+				    val, 2);
+		}
+		unreachable();
+	default:
+		return -EINVAL;
+	}
+}
+
+static int ad3552r_hs_buffer_postenable(struct iio_dev *indio_dev)
+{
+	struct ad3552r_hs_state *st = iio_priv(indio_dev);
+	struct iio_backend_data_fmt fmt = {
+		.type = IIO_BACKEND_DATA_UNSIGNED
+	};
+	int loop_len, val, err;
+
+	/* Inform DAC chip to switch into DDR mode */
+	err = ad3552r_qspi_update_reg_bits(st,
+					   AD3552R_REG_ADDR_INTERFACE_CONFIG_D,
+					   AD3552R_MASK_SPI_CONFIG_DDR,
+					   AD3552R_MASK_SPI_CONFIG_DDR, 1);
+	if (err)
+		return err;
+
+	/* Inform DAC IP to go for DDR mode from now on */
+	err = iio_backend_ddr_enable(st->back);
+	if (err) {
+		dev_warn(st->dev, "could not set DDR mode, not streaming");
+		goto exit_err;
+	}
+
+	st->ddr_mode = true;
+
+	switch (*indio_dev->active_scan_mask) {
+	case AD3552R_CH0_ACTIVE:
+		st->single_channel = true;
+		loop_len = 2;
+		val = AD3552R_REG_ADDR_CH_DAC_16B(0);
+		break;
+	case AD3552R_CH1_ACTIVE:
+		st->single_channel = true;
+		loop_len = 2;
+		val = AD3552R_REG_ADDR_CH_DAC_16B(1);
+		break;
+	case AD3552R_CH0_CH1_ACTIVE:
+		st->single_channel = false;
+		loop_len = 4;
+		val = AD3552R_REG_ADDR_CH_DAC_16B(1);
+		break;
+	default:
+		err = -EINVAL;
+		goto exit_err_ddr;
+	}
+
+	err = st->data->bus_reg_write(st->back, AD3552R_REG_ADDR_STREAM_MODE,
+				      loop_len, 1);
+	if (err)
+		goto exit_err_ddr;
+
+	err = iio_backend_data_transfer_addr(st->back, val);
+	if (err)
+		goto exit_err_ddr;
+
+	err = iio_backend_data_format_set(st->back, 0, &fmt);
+	if (err)
+		goto exit_err_ddr;
+
+	err = iio_backend_data_stream_enable(st->back);
+	if (err)
+		goto exit_err_ddr;
+
+	return 0;
+
+exit_err_ddr:
+	iio_backend_ddr_disable(st->back);
+
+exit_err:
+	ad3552r_qspi_update_reg_bits(st,
+				     AD3552R_REG_ADDR_INTERFACE_CONFIG_D,
+				     AD3552R_MASK_SPI_CONFIG_DDR,
+				     0, 1);
+
+	iio_backend_ddr_disable(st->back);
+
+	st->ddr_mode = false;
+
+	return err;
+}
+
+static int ad3552r_hs_buffer_predisable(struct iio_dev *indio_dev)
+{
+	struct ad3552r_hs_state *st = iio_priv(indio_dev);
+	int err;
+
+	err = iio_backend_data_stream_disable(st->back);
+	if (err)
+		return err;
+
+	/* Inform DAC to set in SDR mode */
+	err = ad3552r_qspi_update_reg_bits(st,
+					   AD3552R_REG_ADDR_INTERFACE_CONFIG_D,
+					   AD3552R_MASK_SPI_CONFIG_DDR,
+					   0, 1);
+	if (err)
+		return err;
+
+	err = iio_backend_ddr_disable(st->back);
+	if (err)
+		return err;
+
+	st->ddr_mode = false;
+
+	return 0;
+}
+
+static int ad3552r_hs_set_output_range(struct ad3552r_hs_state *st,
+				       unsigned int mode)
+{
+	return ad3552r_qspi_update_reg_bits(st,
+				AD3552R_REG_ADDR_CH0_CH1_OUTPUT_RANGE,
+				AD3552R_MASK_CH_OUTPUT_RANGE,
+				FIELD_PREP(AD3552R_MASK_CH0_RANGE, mode) |
+				FIELD_PREP(AD3552R_MASK_CH1_RANGE, mode),
+				1);
+}
+
+static int ad3552r_hs_reset(struct ad3552r_hs_state *st)
+{
+	int err;
+
+	st->reset_gpio = devm_gpiod_get_optional(st->dev,
+						 "reset", GPIOD_OUT_LOW);
+	if (IS_ERR(st->reset_gpio))
+		return PTR_ERR(st->reset_gpio);
+
+	if (st->reset_gpio) {
+		fsleep(10);
+		gpiod_set_value_cansleep(st->reset_gpio, 1);
+	} else {
+		err = ad3552r_qspi_update_reg_bits(st,
+					AD3552R_REG_ADDR_INTERFACE_CONFIG_A,
+					AD3552R_MASK_SOFTWARE_RESET,
+					AD3552R_MASK_SOFTWARE_RESET, 1);
+		if (err)
+			return err;
+	}
+	msleep(100);
+
+	return 0;
+}
+
+static int ad3552r_hs_scratch_pad_test(struct ad3552r_hs_state *st)
+{
+	int err, val;
+
+	err = st->data->bus_reg_write(st->back, AD3552R_REG_ADDR_SCRATCH_PAD,
+				      AD3552R_SCRATCH_PAD_TEST_VAL1, 1);
+	if (err)
+		return err;
+
+	err = st->data->bus_reg_read(st->back, AD3552R_REG_ADDR_SCRATCH_PAD,
+				     &val, 1);
+	if (err)
+		return err;
+
+	if (val != AD3552R_SCRATCH_PAD_TEST_VAL1) {
+		dev_err(st->dev,
+			"SCRATCH_PAD_TEST mismatch. Expected 0x%x, Read 0x%x\n",
+			AD3552R_SCRATCH_PAD_TEST_VAL1, val);
+		return -EIO;
+	}
+
+	err = st->data->bus_reg_write(st->back, AD3552R_REG_ADDR_SCRATCH_PAD,
+				      AD3552R_SCRATCH_PAD_TEST_VAL2, 1);
+	if (err)
+		return err;
+
+	err = st->data->bus_reg_read(st->back, AD3552R_REG_ADDR_SCRATCH_PAD,
+				     &val, 1);
+	if (err)
+		return err;
+
+	if (val != AD3552R_SCRATCH_PAD_TEST_VAL2) {
+		dev_err(st->dev,
+			"SCRATCH_PAD_TEST mismatch. Expected 0x%x, Read 0x%x\n",
+			AD3552R_SCRATCH_PAD_TEST_VAL2, val);
+		return -EIO;
+	}
+
+	return 0;
+}
+
+static int ad3552r_hs_setup_custom_gain(struct ad3552r_hs_state *st,
+					u16 gain, u16 offset)
+{
+	int err;
+
+	err = st->data->bus_reg_write(st->back, AD3552R_REG_ADDR_CH_OFFSET(0),
+				      offset, 1);
+	if (err)
+		return dev_err_probe(st->dev, err, "Error writing register\n");
+
+	err = st->data->bus_reg_write(st->back, AD3552R_REG_ADDR_CH_OFFSET(1),
+				      offset, 1);
+	if (err)
+		return dev_err_probe(st->dev, err, "Error writing register\n");
+
+	err = st->data->bus_reg_write(st->back, AD3552R_REG_ADDR_CH_GAIN(0),
+				      gain, 1);
+	if (err)
+		return dev_err_probe(st->dev, err, "Error writing register\n");
+
+	err = st->data->bus_reg_write(st->back, AD3552R_REG_ADDR_CH_GAIN(1),
+				      gain, 1);
+	if (err)
+		return dev_err_probe(st->dev, err, "Error writing register\n");
+
+	return 0;
+}
+
+static int ad3552r_hs_setup(struct ad3552r_hs_state *st)
+{
+	u8 gs_p, gs_n;
+	s16 goffs;
+	u16 id, rfb;
+	u16 gain = 0, offset = 0;
+	u32 val, range;
+	int err;
+
+	err = ad3552r_hs_reset(st);
+	if (err)
+		return err;
+
+	err = iio_backend_ddr_disable(st->back);
+	if (err)
+		return err;
+
+	err = ad3552r_hs_scratch_pad_test(st);
+	if (err)
+		return err;
+
+	err = st->data->bus_reg_read(st->back, AD3552R_REG_ADDR_PRODUCT_ID_L,
+				     &val, 1);
+	if (err)
+		return err;
+
+	id = val;
+
+	err = st->data->bus_reg_read(st->back, AD3552R_REG_ADDR_PRODUCT_ID_H,
+				     &val, 1);
+	if (err)
+		return err;
+
+	id |= val << 8;
+	if (id != st->model_data->chip_id)
+		dev_info(st->dev, "Chip ID error. Expected 0x%x, Read 0x%x\n",
+			 AD3552R_ID, id);
+
+	err = st->data->bus_reg_write(st->back,
+				      AD3552R_REG_ADDR_SH_REFERENCE_CONFIG,
+				      0, 1);
+	if (err)
+		return err;
+
+	err = st->data->bus_reg_write(st->back,
+				      AD3552R_REG_ADDR_TRANSFER_REGISTER,
+				      AD3552R_MASK_QUAD_SPI |
+				      AD3552R_MASK_STREAM_LENGTH_KEEP_VALUE, 1);
+	if (err)
+		return err;
+
+	err = iio_backend_data_source_set(st->back, 0, IIO_BACKEND_EXTERNAL);
+	if (err)
+		return err;
+
+	err = iio_backend_data_source_set(st->back, 1, IIO_BACKEND_EXTERNAL);
+	if (err)
+		return err;
+
+	err = ad3552r_get_ref_voltage(st->dev);
+	if (err < 0)
+		return err;
+
+	val = err;
+
+	err = ad3552r_qspi_update_reg_bits(st,
+				AD3552R_REG_ADDR_SH_REFERENCE_CONFIG,
+				AD3552R_MASK_REFERENCE_VOLTAGE_SEL,
+				val, 1);
+	if (err)
+		return err;
+
+	err = ad3552r_get_drive_strength(st->dev, &val);
+	if (!err) {
+		err = ad3552r_qspi_update_reg_bits(st,
+					AD3552R_REG_ADDR_INTERFACE_CONFIG_D,
+					AD3552R_MASK_SDO_DRIVE_STRENGTH,
+					val, 1);
+		if (err)
+			return err;
+	}
+
+	struct fwnode_handle *child __free(fwnode_handle) =
+				device_get_named_child_node(st->dev, "channel");
+	if (!child)
+		return -EINVAL;
+
+	/*
+	 * One of "adi,output-range-microvolt" or "custom-output-range-config"
+	 * must be available in fdt.
+	 */
+	err = ad3552r_get_output_range(st->dev, st->model_data, child, &range);
+	if (!err)
+		return ad3552r_hs_set_output_range(st, range);
+	if (err != -ENOENT)
+		return err;
+
+	err = ad3552r_get_custom_gain(st->dev, child, &gs_p, &gs_n, &rfb,
+				      &goffs);
+	if (err)
+		return err;
+
+	gain = ad3552r_calc_custom_gain(gs_p, gs_n, goffs);
+	offset = abs(goffs);
+
+	return ad3552r_hs_setup_custom_gain(st, gain, offset);
+}
+
+static const struct iio_buffer_setup_ops ad3552r_hs_buffer_setup_ops = {
+	.postenable = ad3552r_hs_buffer_postenable,
+	.predisable = ad3552r_hs_buffer_predisable,
+};
+
+#define AD3552R_CHANNEL(ch) { \
+	.type = IIO_VOLTAGE, \
+	.info_mask_separate = BIT(IIO_CHAN_INFO_RAW), \
+	.info_mask_shared_by_all = BIT(IIO_CHAN_INFO_SAMP_FREQ), \
+	.output = 1, \
+	.indexed = 1, \
+	.channel = (ch), \
+	.scan_index = (ch), \
+	.scan_type = { \
+		.sign = 'u', \
+		.realbits = 16, \
+		.storagebits = 16, \
+		.endianness = IIO_BE, \
+	} \
+}
+
+static const struct iio_chan_spec ad3552r_hs_channels[] = {
+	AD3552R_CHANNEL(0),
+	AD3552R_CHANNEL(1),
+};
+
+static const struct iio_info ad3552r_hs_info = {
+	.read_raw = &ad3552r_hs_read_raw,
+	.write_raw = &ad3552r_hs_write_raw,
+};
+
+static int ad3552r_hs_probe(struct platform_device *pdev)
+{
+	struct ad3552r_hs_state *st;
+	struct iio_dev *indio_dev;
+	int ret;
+
+	indio_dev = devm_iio_device_alloc(&pdev->dev, sizeof(*st));
+	if (!indio_dev)
+		return -ENOMEM;
+
+	st = iio_priv(indio_dev);
+	st->dev = &pdev->dev;
+
+	st->data = pdev->dev.platform_data;
+	if (!st->data)
+		dev_err_probe(st->dev, -ENODEV, "No platform data !");
+
+	st->back = devm_iio_backend_get(&pdev->dev, NULL);
+	if (IS_ERR(st->back))
+		return PTR_ERR(st->back);
+
+	ret = devm_iio_backend_enable(&pdev->dev, st->back);
+	if (ret)
+		return ret;
+
+	st->model_data = device_get_match_data(&pdev->dev);
+
+	indio_dev->name = "ad3552r";
+	indio_dev->modes = INDIO_DIRECT_MODE;
+	indio_dev->setup_ops = &ad3552r_hs_buffer_setup_ops;
+	indio_dev->channels = ad3552r_hs_channels;
+	indio_dev->num_channels = ARRAY_SIZE(ad3552r_hs_channels);
+	indio_dev->info = &ad3552r_hs_info;
+
+	ret = devm_iio_backend_request_buffer(&pdev->dev, st->back, indio_dev);
+	if (ret)
+		return ret;
+
+	ret = ad3552r_hs_setup(st);
+	if (ret)
+		return ret;
+
+	return devm_iio_device_register(&pdev->dev, indio_dev);
+}
+
+static const struct ad3552r_model_data ad3552r_model_data = {
+	.model_name = "ad3552r",
+	.chip_id = AD3552R_ID,
+	.num_hw_channels = 2,
+	.ranges_table = ad3552r_ch_ranges,
+	.num_ranges = ARRAY_SIZE(ad3552r_ch_ranges),
+};
+
+static const struct of_device_id ad3552r_hs_of_id[] = {
+	{ .compatible = "adi,ad3552r", .data = &ad3552r_model_data },
+	{ }
+};
+MODULE_DEVICE_TABLE(of, ad3552r_hs_of_id);
+
+static struct platform_driver axi_ad3552r_driver = {
+	.driver = {
+		.name = "ad3552r-axi",
+		.of_match_table = ad3552r_hs_of_id,
+	},
+	.probe = ad3552r_hs_probe,
+};
+module_platform_driver(axi_ad3552r_driver);
+
+MODULE_AUTHOR("Dragos Bogdan <dragos.bogdan@analog.com>");
+MODULE_AUTHOR("Angelo Dureghello <adueghello@baylibre.com>");
+MODULE_DESCRIPTION("AD3552R Driver - AXI IP version");
+MODULE_LICENSE("GPL");
+MODULE_IMPORT_NS(IIO_AD3552R);
diff --git a/drivers/iio/dac/ad3552r.h b/drivers/iio/dac/ad3552r.h
index 088eb8ecfac6..fc00ed4c2565 100644
--- a/drivers/iio/dac/ad3552r.h
+++ b/drivers/iio/dac/ad3552r.h
@@ -38,6 +38,8 @@
 #define AD3552R_REG_ADDR_TRANSFER_REGISTER		0x0F
 #define   AD3552R_MASK_MULTI_IO_MODE			GENMASK(7, 6)
 #define   AD3552R_MASK_STREAM_LENGTH_KEEP_VALUE		BIT(2)
+#define   AD3552R_MASK_DUAL_SPI				BIT(6)
+#define   AD3552R_MASK_QUAD_SPI				BIT(7)
 #define AD3552R_REG_ADDR_INTERFACE_CONFIG_C		0x10
 #define   AD3552R_MASK_CRC_ENABLE			(GENMASK(7, 6) |\
 							 GENMASK(1, 0))
@@ -129,6 +131,11 @@
 #define AD3552R_GAIN_SCALE				1000
 #define AD3552R_LDAC_PULSE_US				100
 
+#define AD3552R_CH0_ACTIVE				BIT(0)
+#define AD3552R_CH1_ACTIVE				BIT(1)
+#define AD3552R_CH0_CH1_ACTIVE				(AD3552R_CH0_ACTIVE | \
+							 AD3552R_CH1_ACTIVE)
+
 #define AD3552R_MAX_RANGES	5
 #define AD3542R_MAX_RANGES	6
 
diff --git a/include/linux/platform_data/ad3552r-hs.h b/include/linux/platform_data/ad3552r-hs.h
new file mode 100644
index 000000000000..4e3213a0c73b
--- /dev/null
+++ b/include/linux/platform_data/ad3552r-hs.h
@@ -0,0 +1,18 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/*
+ * Copyright (c) 2010-2024 Analog Devices Inc.
+ * Copyright (c) 2024 Baylibre, SAS
+ */
+#ifndef __LINUX_PLATFORM_DATA_AD3552R_HS_H__
+#define __LINUX_PLATFORM_DATA_AD3552R_HS_H__
+
+#include <linux/iio/backend.h>
+
+struct ad3552r_hs_platform_data {
+	int (*bus_reg_read)(struct iio_backend *back, u32 reg, u32 *val,
+			    size_t data_size);
+	int (*bus_reg_write)(struct iio_backend *back, u32 reg, u32 val,
+			     size_t data_size);
+};
+
+#endif /* __LINUX_PLATFORM_DATA_AD3552R_HS_H__ */

-- 
2.45.0.rc1

On Tue, 08 Oct 2024 17:43:41 +0200
Angelo Dureghello <adureghello@baylibre.com> wrote:

> From: Angelo Dureghello <adureghello@baylibre.com>
> 
> Add High Speed ad3552r platform driver.
> 
> The ad3552r DAC is controlled by a custom (fpga-based) DAC IP
> through the current AXI backend, or similar alternative IIO backend.
> 
> Compared to the existing driver (ad3552r.c), that is a simple SPI
> driver, this driver is coupled with a DAC IIO backend that finally
> controls the ad3552r by a fpga-based "QSPI+DDR" interface, to reach
> maximum transfer rate of 33MUPS using dma stream capabilities.
> 
> All commands involving QSPI bus read/write are delegated to the backend
> through the provided APIs for bus read/write.
> 
> Signed-off-by: Angelo Dureghello <adureghello@baylibre.com>
> ---
>  drivers/iio/dac/Kconfig                  |  14 +
>  drivers/iio/dac/Makefile                 |   1 +
>  drivers/iio/dac/ad3552r-hs.c             | 526 +++++++++++++++++++++++++++++++
>  drivers/iio/dac/ad3552r.h                |   7 +
>  include/linux/platform_data/ad3552r-hs.h |  18 ++
I'd missed this before.  No obvious reason to put the include in a 'global' location
when for now at least only includers re in drivers/iio/dac/

So please move it there.

Some stuff include/linux/platform_data/ is ancient things dating back to board file
days.

Other than that and things bit Nuno raised, this series looks good to me.
Please drop the first 2 patches from v6 as I've applied those now.

Jonathan


> diff --git a/include/linux/platform_data/ad3552r-hs.h b/include/linux/platform_data/ad3552r-hs.h
> new file mode 100644
> index 000000000000..4e3213a0c73b
> --- /dev/null
> +++ b/include/linux/platform_data/ad3552r-hs.h

This isn't what we'd think of as 'platform_data' normally and it is only used
in drivers/iio/dac/ so I would simply move the header to drivers/iio/dac/ad3552r-hs.h

> @@ -0,0 +1,18 @@
> +/* SPDX-License-Identifier: GPL-2.0-or-later */
> +/*
> + * Copyright (c) 2010-2024 Analog Devices Inc.

Generous on the years.  This one should probably just be new copyright given
the code is effectively new.

> + * Copyright (c) 2024 Baylibre, SAS
> + */
> +#ifndef __LINUX_PLATFORM_DATA_AD3552R_HS_H__
> +#define __LINUX_PLATFORM_DATA_AD3552R_HS_H__
> +
> +#include <linux/iio/backend.h>
For this use a forwards reference

struct iio_backend;

Nice to avoid nests of includes where we can easily do so.

> +
> +struct ad3552r_hs_platform_data {
> +	int (*bus_reg_read)(struct iio_backend *back, u32 reg, u32 *val,
> +			    size_t data_size);
> +	int (*bus_reg_write)(struct iio_backend *back, u32 reg, u32 val,
> +			     size_t data_size);
> +};
> +
> +#endif /* __LINUX_PLATFORM_DATA_AD3552R_HS_H__ */
>