Add a generic driver to support sigma delta modulators.
Typically, this device is a hardware connected to an IIO device
in charge of the conversion. The device is exposed as an IIO backend
device. This backend device and the associated conversion device
can be seen as an aggregate device from IIO framework.
Signed-off-by: Olivier Moysan <olivier.moysan@xxxxxxxxxxx>
---
drivers/iio/adc/Kconfig | 10 +++
drivers/iio/adc/Makefile | 1 +
drivers/iio/adc/sd_adc_backend.c | 110 +++++++++++++++++++++++++++++++
3 files changed, 121 insertions(+)
create mode 100644 drivers/iio/adc/sd_adc_backend.c
diff --git a/drivers/iio/adc/Kconfig b/drivers/iio/adc/Kconfig
index 3d91015af6ea..f3dfdaa80678 100644
--- a/drivers/iio/adc/Kconfig
+++ b/drivers/iio/adc/Kconfig
@@ -1155,6 +1155,16 @@ config SPEAR_ADC
To compile this driver as a module, choose M here: the
module will be called spear_adc.
+config SD_ADC_BACKEND
+ tristate "Generic sigma delta modulator IIO backend"
+ select IIO_BACKEND
+ help
+ Select this option to enables sigma delta modulator. This driver can
+ support generic sigma delta modulators, as IIO backend devices.
+
+ This driver can also be built as a module. If so, the module
+ will be called sd_adc_backend.
+
config SD_ADC_MODULATOR
tristate "Generic sigma delta modulator"
select IIO_BUFFER
diff --git a/drivers/iio/adc/Makefile b/drivers/iio/adc/Makefile
index 37ac689a0209..9aee2e4307d7 100644
--- a/drivers/iio/adc/Makefile
+++ b/drivers/iio/adc/Makefile
@@ -139,3 +139,4 @@ obj-$(CONFIG_VIPERBOARD_ADC) += viperboard_adc.o
obj-$(CONFIG_XILINX_AMS) += xilinx-ams.o
xilinx-xadc-y := xilinx-xadc-core.o xilinx-xadc-events.o
obj-$(CONFIG_XILINX_XADC) += xilinx-xadc.o
+obj-$(CONFIG_SD_ADC_BACKEND) += sd_adc_backend.o
diff --git a/drivers/iio/adc/sd_adc_backend.c b/drivers/iio/adc/sd_adc_backend.c
new file mode 100644
index 000000000000..556a49dc537b
--- /dev/null
+++ b/drivers/iio/adc/sd_adc_backend.c
@@ -0,0 +1,110 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Generic sigma delta modulator IIO backend
+ *
+ * Copyright (C) 2024, STMicroelectronics - All Rights Reserved
+ */
+
+#include <linux/iio/backend.h>
+#include <linux/iio/iio.h>
+#include <linux/module.h>
+#include <linux/mod_devicetable.h>
+#include <linux/platform_device.h>
+#include <linux/regulator/consumer.h>
+
+struct iio_sd_backend_priv {
+ struct regulator *vref;
+ int vref_mv;
+};
+
+static int sd_backend_enable(struct iio_backend *backend)
+{
+ struct iio_sd_backend_priv *priv = iio_backend_get_priv(backend);
+
+ return regulator_enable(priv->vref);
+};
+
+static void sd_backend_disable(struct iio_backend *backend)
+{
+ struct iio_sd_backend_priv *priv = iio_backend_get_priv(backend);
+
+ regulator_disable(priv->vref);
+};
+
+static int sd_backend_read(struct iio_backend *backend, int *val, int *val2, long mask)
+{
+ struct iio_sd_backend_priv *priv = iio_backend_get_priv(backend);
+
+ switch (mask) {
+ case IIO_CHAN_INFO_SCALE:
+ *val = priv->vref_mv;
+ *val2 = 0;
+ return IIO_VAL_INT;
+
+ case IIO_CHAN_INFO_OFFSET:
+ *val = 0;
+ *val2 = 0;
+ return IIO_VAL_INT;
+ }
+
+ return -EINVAL;
+};
+
+static const struct iio_backend_ops sd_backend_ops = {
+ .enable = sd_backend_enable,
+ .disable = sd_backend_disable,
+ .read_raw = sd_backend_read,
+};
+
+static int iio_sd_backend_probe(struct platform_device *pdev)
+{
+ struct device *dev = &pdev->dev;
+ struct regulator *vref;
+ struct iio_sd_backend_priv *priv;
+ int ret;
+
+ priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
+ if (!priv)
+ return -ENOMEM;
+
+ vref = devm_regulator_get_optional(dev, "vref");
+ if (IS_ERR(vref)) {
+ if (PTR_ERR(vref) != -ENODEV)
+ return dev_err_probe(dev, PTR_ERR(vref), "Failed to get vref\n");
+ } else {
+ ret = regulator_get_voltage(vref);
+ if (ret < 0)
+ return ret;
+
+ priv->vref = vref;
+ priv->vref_mv = ret / 1000;
+ }
+
+ ret = devm_iio_backend_register(&pdev->dev, &sd_backend_ops, priv);
+ if (ret)
+ return ret;
+
+ return 0;
+};
+
+static const struct of_device_id sd_backend_of_match[] = {
+ { .compatible = "sd-backend" },
+ { .compatible = "ads1201" },
+ { }
+};
+MODULE_DEVICE_TABLE(of, sd_backend_of_match);
+
+static struct platform_driver iio_sd_backend_adc = {
+ .driver = {
+ .name = "iio_sd_adc_backend",
+ .of_match_table = sd_backend_of_match,
+ },
+ .probe = iio_sd_backend_probe,
+};
+
+module_platform_driver(iio_sd_backend_adc);
+
+MODULE_DESCRIPTION("Basic sigma delta modulator IIO backend");
+MODULE_AUTHOR("Olivier Moysan <olivier.moysan@xxxxxxxxxxx>");
+MODULE_LICENSE("GPL");
+MODULE_IMPORT_NS(IIO_BACKEND);
--
2.25.1
