[PATCH v6 0/2] Maxim MAX1241 driver

[PATCH v6 0/2] Maxim MAX1241 driver

[Alexandru Lazar]

Hi everyone,

Here's version 6 of a patch series which adds support for the Maxim
MAX1241, a 12-bit, single-channel, SPI-connected ADC.

Changelog so far:

v6:

* Add separate cleanup actions for vdd and vref regulators respectively
* Change shdn pin name to shutdown. shdn is what the datasheet calls it
  but "shutdown" seems to be semi-standard, at least in the bindings
  (Rob orriginally suggested that I change the name in the docs. Figured
  it made zero sense to have it bear another name in the code)
* Dropped maxItems property in vref binding, made binding dual-licensed
* Changed name of spi node in binding example 

v5:

* Add vdd supply binding
* Reorder include headers -- one of them had escaped the long mechanized
  hand of the Alphabetron
* Drop scan_index and scan_type from channel spec, as the driver
  doesn't support buffered modes
* Drop a useless initialization of a local variable in probe function
* Revise dt-bindings patch subject line, revise maintainer and
  copyright to match the Signed-off: string, drop reference to driver
  from bindings description
* Various readability/cosmetic fixes

v4:

* Dropped explicit documentation of SPI reg property
* Reordered patch series so that dt bindings come first

v3:

* Fixed silly copy-paste error in Kconfig description

v2:

* Removed useeless header includes
* Dropped needlessly verbose stuff in _read and _probe functions
* Dropped useless GPL notice
* Lowered log level of shdn pin status in probe function, now it's
  dev_dbg
* Added proper error checking for the GPIO shutdown pin
* remove now always returns zero (man, I've been wrong about this for
  *years* now...)
* Added regulator disable action, cleanup is now handled via devm
* Drop delay_usecs, use delay.value, delay.unit
* Drop config_of, of_match_ptr call
* Dropped IIO_BUFFER, IIO_TRIGGERED_BUFFER dependencies, set SPI_MASTER
  as dependency, fix indenting.
* DT binding: use correct id, add reg description (looks pretty
  standard), dropped spi-max-frequency, fixed dt_binding_check
  complaints (oops!)

Alexandru Lazar (2):
  dt-bindings: iio: adc: Add MAX1241 bindings
  iio: adc: Add MAX1241 driver

 .../bindings/iio/adc/maxim,max1241.yaml       |  64 +++++
 drivers/iio/adc/Kconfig                       |  10 +
 drivers/iio/adc/Makefile                      |   1 +
 drivers/iio/adc/max1241.c                     | 227 ++++++++++++++++++
 4 files changed, 302 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/iio/adc/maxim,max1241.yaml
 create mode 100644 drivers/iio/adc/max1241.c

-- 
2.20.1

[PATCH v6 1/2] dt-bindings: iio: adc: Add MAX1241 bindings

[Alexandru Lazar]

Add device-tree bindings documentation for the MAX1241 device driver.

Signed-off-by: Alexandru Lazar <alazar@startmail.com>
---
 .../bindings/iio/adc/maxim,max1241.yaml       | 64 +++++++++++++++++++
 1 file changed, 64 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/iio/adc/maxim,max1241.yaml

diff --git a/Documentation/devicetree/bindings/iio/adc/maxim,max1241.yaml b/Documentation/devicetree/bindings/iio/adc/maxim,max1241.yaml
new file mode 100644
index 000000000000..7da9e4153ac1
--- /dev/null
+++ b/Documentation/devicetree/bindings/iio/adc/maxim,max1241.yaml
@@ -0,0 +1,64 @@
+# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
+# Copyright 2020 Alexandru Lazar
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/iio/adc/maxim,max1241.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Maxim MAX1241 12-bit, single-channel analog to digital converter
+
+maintainers:
+  - Alexandru Lazar <alazar@startmail.com>
+
+description: |
+  Bindings for the max1241 12-bit, single-channel ADC device. Datasheet
+  can be found at:
+    https://datasheets.maximintegrated.com/en/ds/MAX1240-MAX1241.pdf
+
+properties:
+  compatible:
+    enum:
+      - maxim,max1241
+
+  reg:
+    maxItems: 1
+
+  vdd-supply:
+    description:
+      Device tree identifier of the regulator that powers the ADC.
+
+  vref-supply:
+    description:
+      Device tree identifier of the regulator that provides the external
+      reference voltage.
+    maxItems: 1
+
+  shutdown-gpios:
+    description:
+      GPIO spec for the GPIO pin connected to the ADC's /SHDN pin. If
+      specified, the /SHDN pin will be asserted between conversions,
+      thus enabling power-down mode.
+    maxItems: 1
+
+required:
+  - compatible
+  - reg
+  - vdd-supply
+  - vref-supply
+
+examples:
+  - |
+    #include <dt-bindings/gpio/gpio.h>
+    spi {
+      #address-cells = <1>;
+      #size-cells = <0>;
+
+        adc@0 {
+            compatible = "maxim,max1241";
+            reg = <0>;
+            vdd-supply = <&adc_vdd>;
+            vref-supply = <&adc_vref>;
+            spi-max-frequency = <1000000>;
+            shutdown-gpios = <&gpio 26 1>;
+        };
+    };
-- 
2.20.1

[PATCH v6 2/2] iio: adc: Add MAX1241 driver

[Alexandru Lazar]

Add driver for the Maxim MAX1241 12-bit, single-channel ADC.

Reviewed-by: Alexandru Ardelean <alexandru.ardelean@analog.com>
Signed-off-by: Alexandru Lazar <alazar@startmail.com>
---
 drivers/iio/adc/Kconfig   |  10 ++
 drivers/iio/adc/Makefile  |   1 +
 drivers/iio/adc/max1241.c | 227 ++++++++++++++++++++++++++++++++++++++
 3 files changed, 238 insertions(+)
 create mode 100644 drivers/iio/adc/max1241.c

diff --git a/drivers/iio/adc/Kconfig b/drivers/iio/adc/Kconfig
index 5d8540b7b427..55f6462cd93f 100644
--- a/drivers/iio/adc/Kconfig
+++ b/drivers/iio/adc/Kconfig
@@ -566,6 +566,16 @@ config MAX1118
 	  To compile this driver as a module, choose M here: the module will be
 	  called max1118.
 
+config MAX1241
+	tristate "Maxim max1241 ADC driver"
+	depends on SPI_MASTER
+	help
+	  Say yes here to build support for Maxim max1241 12-bit, single-channel
+	  ADC.
+
+	  To compile this driver as a module, choose M here: the module will be
+	  called max1241.
+
 config MAX1363
 	tristate "Maxim max1363 ADC driver"
 	depends on I2C
diff --git a/drivers/iio/adc/Makefile b/drivers/iio/adc/Makefile
index a1f1fbec0f87..37d6f17559dc 100644
--- a/drivers/iio/adc/Makefile
+++ b/drivers/iio/adc/Makefile
@@ -54,6 +54,7 @@ obj-$(CONFIG_LTC2497) += ltc2497.o
 obj-$(CONFIG_MAX1027) += max1027.o
 obj-$(CONFIG_MAX11100) += max11100.o
 obj-$(CONFIG_MAX1118) += max1118.o
+obj-$(CONFIG_MAX1241) += max1241.o
 obj-$(CONFIG_MAX1363) += max1363.o
 obj-$(CONFIG_MAX9611) += max9611.o
 obj-$(CONFIG_MCP320X) += mcp320x.o
diff --git a/drivers/iio/adc/max1241.c b/drivers/iio/adc/max1241.c
new file mode 100644
index 000000000000..541939c7abca
--- /dev/null
+++ b/drivers/iio/adc/max1241.c
@@ -0,0 +1,227 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * MAX1241 low-power, 12-bit serial ADC
+ *
+ * Datasheet: https://datasheets.maximintegrated.com/en/ds/MAX1240-MAX1241.pdf
+ */
+
+#include <linux/delay.h>
+#include <linux/gpio/consumer.h>
+#include <linux/iio/iio.h>
+#include <linux/module.h>
+#include <linux/regulator/consumer.h>
+#include <linux/spi/spi.h>
+
+#define MAX1241_VAL_MASK GENMASK(11, 0)
+#define MAX1241_SHUTDOWN_DELAY_USEC 4
+
+enum max1241_id {
+	max1241,
+};
+
+struct max1241 {
+	struct spi_device *spi;
+	struct mutex lock;
+	struct regulator *vdd;
+	struct regulator *vref;
+	struct gpio_desc *shutdown;
+
+	__be16 data ____cacheline_aligned;
+};
+
+static const struct iio_chan_spec max1241_channels[] = {
+	{
+		.type = IIO_VOLTAGE,
+		.indexed = 1,
+		.channel = 0,
+		.info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |
+				BIT(IIO_CHAN_INFO_SCALE),
+	},
+};
+
+static int max1241_read(struct max1241 *adc)
+{
+	struct spi_transfer xfers[] = {
+		/*
+		 * Begin conversion by bringing /CS low for at least
+		 * tconv us.
+		 */
+		{
+			.len = 0,
+			.delay.value = 8,
+			.delay.unit = SPI_DELAY_UNIT_USECS,
+		},
+		/*
+		 * Then read two bytes of data in our RX buffer.
+		 */
+		{
+			.rx_buf = &adc->data,
+			.len = 2,
+		},
+	};
+
+	return spi_sync_transfer(adc->spi, xfers, ARRAY_SIZE(xfers));
+}
+
+static int max1241_read_raw(struct iio_dev *indio_dev,
+			struct iio_chan_spec const *chan,
+			int *val, int *val2, long mask)
+{
+	int ret, vref_uV;
+	struct max1241 *adc = iio_priv(indio_dev);
+
+	switch (mask) {
+	case IIO_CHAN_INFO_RAW:
+		mutex_lock(&adc->lock);
+
+		if (adc->shutdown) {
+			gpiod_set_value(adc->shutdown, 0);
+			udelay(MAX1241_SHUTDOWN_DELAY_USEC);
+			ret = max1241_read(adc);
+			gpiod_set_value(adc->shutdown, 1);
+		} else
+			ret = max1241_read(adc);
+
+		if (ret) {
+			mutex_unlock(&adc->lock);
+			return ret;
+		}
+
+		*val = (be16_to_cpu(adc->data) >> 3) & MAX1241_VAL_MASK;
+
+		mutex_unlock(&adc->lock);
+		return IIO_VAL_INT;
+	case IIO_CHAN_INFO_SCALE:
+		vref_uV = regulator_get_voltage(adc->vref);
+
+		if (vref_uV < 0)
+			return vref_uV;
+
+		*val = vref_uV / 1000;
+		*val2 = 12;
+
+		return IIO_VAL_FRACTIONAL_LOG2;
+	default:
+		return -EINVAL;
+	}
+}
+
+static const struct iio_info max1241_info = {
+	.read_raw = max1241_read_raw,
+};
+
+static void max1241_disable_vdd_action(void *data)
+{
+	struct max1241 *adc = data;
+	struct device *dev = &adc->spi->dev;
+	int err;
+
+	err = regulator_disable(adc->vdd);
+	if (err)
+		dev_err(dev, "could not disable vdd regulator.\n");
+}
+
+static void max1241_disable_vref_action(void *data)
+{
+	struct max1241 *adc = data;
+	struct device *dev = &adc->spi->dev;
+	int err;
+
+	err = regulator_disable(adc->vref);
+	if (err)
+		dev_err(dev, "could not disable vref regulator.\n");
+}
+
+static int max1241_probe(struct spi_device *spi)
+{
+	struct device *dev = &spi->dev;
+	struct iio_dev *indio_dev;
+	struct max1241 *adc;
+	int ret;
+
+	indio_dev = devm_iio_device_alloc(dev, sizeof(*adc));
+	if (!indio_dev)
+		return -ENOMEM;
+
+	adc = iio_priv(indio_dev);
+	adc->spi = spi;
+	mutex_init(&adc->lock);
+
+	spi_set_drvdata(spi, indio_dev);
+
+	adc->vdd = devm_regulator_get(dev, "vdd");
+	if (IS_ERR(adc->vdd)) {
+		dev_err(dev, "failed to get vdd regulator\n");
+		return PTR_ERR(adc->vdd);
+	}
+
+	ret = regulator_enable(adc->vdd);
+	if (ret)
+		return ret;
+
+	ret = devm_add_action_or_reset(dev, max1241_disable_vdd_action, adc);
+	if (ret) {
+		dev_err(dev, "could not set up vdd regulator cleanup action\n");
+		return ret;
+	}
+
+	adc->vref = devm_regulator_get(dev, "vref");
+	if (IS_ERR(adc->vref)) {
+		dev_err(dev, "failed to get vref regulator\n");
+		return PTR_ERR(adc->vref);
+	}
+
+	ret = regulator_enable(adc->vref);
+	if (ret)
+		return ret;
+
+	ret = devm_add_action_or_reset(dev, max1241_disable_vref_action, adc);
+	if (ret) {
+		dev_err(dev, "could not set up vref regulator cleanup action\n");
+		return ret;
+	}
+
+	adc->shutdown = devm_gpiod_get_optional(dev, "shutdown",
+						GPIOD_OUT_HIGH);
+	if (IS_ERR(adc->shutdown))
+		return PTR_ERR(adc->shutdown);
+
+	if (adc->shutdown)
+		dev_dbg(dev, "shutdown pin passed, low-power mode enabled");
+	else
+		dev_dbg(dev, "no shutdown pin passed, low-power mode disabled");
+
+	indio_dev->name = spi_get_device_id(spi)->name;
+	indio_dev->dev.parent = dev;
+	indio_dev->info = &max1241_info;
+	indio_dev->modes = INDIO_DIRECT_MODE;
+	indio_dev->channels = max1241_channels;
+	indio_dev->num_channels = ARRAY_SIZE(max1241_channels);
+
+	return devm_iio_device_register(dev, indio_dev);
+}
+
+static const struct spi_device_id max1241_id[] = {
+	{ "max1241", max1241 },
+	{}
+};
+
+static const struct of_device_id max1241_dt_ids[] = {
+	{ .compatible = "maxim,max1241" },
+	{}
+};
+MODULE_DEVICE_TABLE(of, max1241_dt_ids);
+
+static struct spi_driver max1241_spi_driver = {
+	.driver = {
+		.name = "max1241",
+		.of_match_table = max1241_dt_ids,
+	},
+	.probe = max1241_probe,
+	.id_table = max1241_id,
+};
+module_spi_driver(max1241_spi_driver);
+
+MODULE_AUTHOR("Alexandru Lazar <alazar@startmail.com>");
+MODULE_DESCRIPTION("MAX1241 ADC driver");
+MODULE_LICENSE("GPL v2");
-- 
2.20.1

Re: [PATCH v6 2/2] iio: adc: Add MAX1241 driver

[Andy Shevchenko]

On Wed, Apr 1, 2020 at 9:47 PM Alexandru Lazar <alazar@startmail.com> wrote:
>
> Add driver for the Maxim MAX1241 12-bit, single-channel ADC.
>

Perhaps put data sheet link as Datasheet: tag here?

> Reviewed-by: Alexandru Ardelean <alexandru.ardelean@analog.com>
> Signed-off-by: Alexandru Lazar <alazar@startmail.com>

...

> +       indio_dev->name = spi_get_device_id(spi)->name;

Shouldn't be rather part number?
Jonathan?

-- 
With Best Regards,
Andy Shevchenko

Re: [PATCH v6 2/2] iio: adc: Add MAX1241 driver

[Lars-Peter Clausen]

On 4/2/20 8:45 PM, Andy Shevchenko wrote:
> On Wed, Apr 1, 2020 at 9:47 PM Alexandru Lazar <alazar@startmail.com> wrote:
>> Add driver for the Maxim MAX1241 12-bit, single-channel ADC.
>>
> Perhaps put data sheet link as Datasheet: tag here?
>
>> Reviewed-by: Alexandru Ardelean <alexandru.ardelean@analog.com>
>> Signed-off-by: Alexandru Lazar <alazar@startmail.com>
> ...
>
>> +       indio_dev->name = spi_get_device_id(spi)->name;
> Shouldn't be rather part number?
> Jonathan?

This is the part number as defined in the spi_device id table :)

+static const struct spi_device_id max1241_id[] = {
+	{ "max1241", max1241 },
+	{}
+};

- Lars

Re: [PATCH v6 2/2] iio: adc: Add MAX1241 driver

[Andy Shevchenko]

On Thu, Apr 2, 2020 at 9:55 PM Lars-Peter Clausen <lars@metafoo.de> wrote:
> On 4/2/20 8:45 PM, Andy Shevchenko wrote:
> > On Wed, Apr 1, 2020 at 9:47 PM Alexandru Lazar <alazar@startmail.com> wrote:
> >> Add driver for the Maxim MAX1241 12-bit, single-channel ADC.
> >>
> > Perhaps put data sheet link as Datasheet: tag here?
> >
> >> Reviewed-by: Alexandru Ardelean <alexandru.ardelean@analog.com>
> >> Signed-off-by: Alexandru Lazar <alazar@startmail.com>
> > ...
> >
> >> +       indio_dev->name = spi_get_device_id(spi)->name;
> > Shouldn't be rather part number?
> > Jonathan?
>
> This is the part number as defined in the spi_device id table :)

Okay!

> +static const struct spi_device_id max1241_id[] = {
> +       { "max1241", max1241 },
> +       {}
> +};


-- 
With Best Regards,
Andy Shevchenko

Re: [PATCH v6 2/2] iio: adc: Add MAX1241 driver

[Alexandru Lazar]

On Thu, Apr 02, 2020 at 09:45:32PM +0300, Andy Shevchenko wrote:
> On Wed, Apr 1, 2020 at 9:47 PM Alexandru Lazar <alazar@startmail.com> wrote:
> >
> > Add driver for the Maxim MAX1241 12-bit, single-channel ADC.
> >
> 
> Perhaps put data sheet link as Datasheet: tag here?

Sure, makes sense. I'll send a v7 in a jiffy.