iio: adc: adi-axi-adc: add platform children support

This is a preparation for the next commit adding support for register
read and write functions on AD7606.
Since sometimes a bus will be used, it has been agreed during ad3552's
driver implementation that the device's driver bus is the backend, whose
device node will be a child node.
To provide the special callbacks for setting the register, axi-adc needs
to pass them to the child device's driver through platform data.

Signed-off-by: Angelo Dureghello <adureghello@baylibre.com>
Link: https://patch.msgid.link/20250210-wip-bl-ad7606_add_backend_sw_mode-v4-5-160df18b1da7@baylibre.com
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

2 files changed, 81 insertions, 0 deletions

diff --git a/drivers/iio/adc/ad7606_bus_iface.h b/drivers/iio/adc/ad7606_bus_iface.h
new file mode 100644
index 000000000000..f2c979a9b7f3
--- /dev/null
+++ b/drivers/iio/adc/ad7606_bus_iface.h
@@ -0,0 +1,16 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/*
+ * Copyright (c) 2010-2024 Analog Devices Inc.
+ * Copyright (c) 2025 Baylibre, SAS
+ */
+#ifndef __LINUX_PLATFORM_DATA_AD7606_H__
+#define __LINUX_PLATFORM_DATA_AD7606_H__
+
+struct iio_backend;
+
+struct ad7606_platform_data {
+	int (*bus_reg_read)(struct iio_backend *back, u32 reg, u32 *val);
+	int (*bus_reg_write)(struct iio_backend *back, u32 reg, u32 val);
+};
+
+#endif /* __LINUX_PLATFORM_DATA_AD7606_H__ */
diff --git a/drivers/iio/adc/adi-axi-adc.c b/drivers/iio/adc/adi-axi-adc.c
index 04f7d7d3890b..182ad14e4949 100644
--- a/drivers/iio/adc/adi-axi-adc.c
+++ b/drivers/iio/adc/adi-axi-adc.c
@@ -334,6 +334,36 @@ static const struct regmap_config axi_adc_regmap_config = {
 	.reg_stride = 4,
 };
 
+static void axi_adc_child_remove(void *data)
+{
+	platform_device_unregister(data);
+}
+
+static int axi_adc_create_platform_device(struct adi_axi_adc_state *st,
+					  struct fwnode_handle *child)
+{
+	struct platform_device_info pi = {
+	    .parent = st->dev,
+	    .name = fwnode_get_name(child),
+	    .id = PLATFORM_DEVID_AUTO,
+	    .fwnode = child,
+	    .data = st->info->pdata,
+	    .size_data = st->info->pdata_sz,
+	};
+	struct platform_device *pdev;
+	int ret;
+
+	pdev = platform_device_register_full(&pi);
+	if (IS_ERR(pdev))
+		return PTR_ERR(pdev);
+
+	ret = devm_add_action_or_reset(st->dev, axi_adc_child_remove, pdev);
+	if (ret)
+		return ret;
+
+	return 0;
+}
+
 static const struct iio_backend_ops adi_axi_adc_ops = {
 	.enable = axi_adc_enable,
 	.disable = axi_adc_disable,
@@ -417,6 +447,28 @@ static int adi_axi_adc_probe(struct platform_device *pdev)
 		return dev_err_probe(&pdev->dev, ret,
 				     "failed to register iio backend\n");
 
+	device_for_each_child_node_scoped(&pdev->dev, child) {
+		int val;
+
+		if (!st->info->has_child_nodes)
+			return dev_err_probe(&pdev->dev, -EINVAL,
+					     "invalid fdt axi-dac compatible.");
+
+		/* Processing only reg 0 node */
+		ret = fwnode_property_read_u32(child, "reg", &val);
+		if (ret)
+			return dev_err_probe(&pdev->dev, ret,
+					     "invalid reg property.");
+		if (val != 0)
+			return dev_err_probe(&pdev->dev, -EINVAL,
+					     "invalid node address.");
+
+		ret = axi_adc_create_platform_device(st, child);
+		if (ret)
+			return dev_err_probe(&pdev->dev, -EINVAL,
+					     "cannot create device.");
+	}
+
 	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),
@@ -430,6 +482,19 @@ static const struct axi_adc_info adc_generic = {
 	.backend_info = &adi_axi_adc_generic,
 };
 
+static const struct ad7606_platform_data ad7606_pdata = {
+	.bus_reg_read = ad7606_bus_reg_read,
+	.bus_reg_write = ad7606_bus_reg_write,
+};
+
+static const struct axi_adc_info adc_ad7606 = {
+	.version = ADI_AXI_PCORE_VER(10, 0, 'a'),
+	.backend_info = &adi_axi_adc_generic,
+	.pdata = &ad7606_pdata,
+	.pdata_sz = sizeof(ad7606_pdata),
+	.has_child_nodes = true,
+};
+
 /* 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 = &adc_generic },