[PATCH v4 1/2] dt-bindings: iio: adc: Add TI ADS1100 and ADS1000

[PATCH v4 1/2] dt-bindings: iio: adc: Add TI ADS1100 and ADS1000

[Mike Looijmans]

The ADS1100 is a 16-bit ADC (at 8 samples per second).
The ADS1000 is similar, but has a fixed data rate.

Signed-off-by: Mike Looijmans <mike.looijmans@topic.nl>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>

---

(no changes since v2)

Changes in v2:
"reg" property is mandatory.
Add vdd-supply and #io-channel-cells

 .../bindings/iio/adc/ti,ads1100.yaml          | 46 +++++++++++++++++++
 1 file changed, 46 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/iio/adc/ti,ads1100.yaml

diff --git a/Documentation/devicetree/bindings/iio/adc/ti,ads1100.yaml b/Documentation/devicetree/bindings/iio/adc/ti,ads1100.yaml
new file mode 100644
index 000000000000..970ccab15e1e
--- /dev/null
+++ b/Documentation/devicetree/bindings/iio/adc/ti,ads1100.yaml
@@ -0,0 +1,46 @@
+# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/iio/adc/ti,ads1100.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: TI ADS1100/ADS1000 single channel I2C analog to digital converter
+
+maintainers:
+  - Mike Looijmans <mike.looijmans@topic.nl>
+
+description: |
+  Datasheet at: https://www.ti.com/lit/gpn/ads1100
+
+properties:
+  compatible:
+    enum:
+      - ti,ads1100
+      - ti,ads1000
+
+  reg:
+    maxItems: 1
+
+  vdd-supply: true
+
+  "#io-channel-cells":
+    const: 0
+
+required:
+  - compatible
+  - reg
+
+additionalProperties: false
+
+examples:
+  - |
+    i2c {
+        #address-cells = <1>;
+        #size-cells = <0>;
+
+        adc@49 {
+            compatible = "ti,ads1100";
+            reg = <0x49>;
+        };
+    };
+...
-- 
2.17.1


Met vriendelijke groet / kind regards,

Mike Looijmans
System Expert


TOPIC Embedded Products B.V.
Materiaalweg 4, 5681 RJ Best
The Netherlands

T: +31 (0) 499 33 69 69
E: mike.looijmans@topicproducts.com
W: www.topic.nl

Please consider the environment before printing this e-mail

[PATCH v4 2/2] iio: adc: Add TI ADS1100 and ADS1000

[Mike Looijmans]

The ADS1100 is a 16-bit ADC (at 8 samples per second).
The ADS1000 is similar, but has a fixed data rate.

Signed-off-by: Mike Looijmans <mike.looijmans@topic.nl>

---

Changes in v4:
Use post-increment
Formatting fixes (commas, indents, empty line)
Use 'ffs' and explain gain formula
Use dev_set_drvdata/dev_get_drvdata for pm_ methods
Use units.h for micro-to-milli conversion

Changes in v3:
Add #include linux/bitfield.h and linux/bits.h

Changes in v2:
Remove "driver for" from title
Use proper PM_RUNTIME macros
Fix indents
Use dev_err_probe()
Unsigned index and post-increment
Use GENMASK and FIELD_GET
remove ads1100_set_conv_mode
remove Kconfig BUFFER dependencies
remove unused #include
Set SCALE instead of HARDWAREGAIN
Use devm_add_action_or_reset

 drivers/iio/adc/Kconfig      |  10 +
 drivers/iio/adc/Makefile     |   1 +
 drivers/iio/adc/ti-ads1100.c | 442 +++++++++++++++++++++++++++++++++++
 3 files changed, 453 insertions(+)
 create mode 100644 drivers/iio/adc/ti-ads1100.c

diff --git a/drivers/iio/adc/Kconfig b/drivers/iio/adc/Kconfig
index 63f80d747cbd..257efb25a92e 100644
--- a/drivers/iio/adc/Kconfig
+++ b/drivers/iio/adc/Kconfig
@@ -1207,6 +1207,16 @@ config TI_ADS1015
 	  This driver can also be built as a module. If so, the module will be
 	  called ti-ads1015.
 
+config TI_ADS1100
+	tristate "Texas Instruments ADS1100 and ADS1000 ADC"
+	depends on I2C
+	help
+	  If you say yes here you get support for Texas Instruments ADS1100 and
+	  ADS1000 ADC chips.
+
+	  This driver can also be built as a module. If so, the module will be
+	  called ti-ads1100.
+
 config TI_ADS7950
 	tristate "Texas Instruments ADS7950 ADC driver"
 	depends on SPI && GPIOLIB
diff --git a/drivers/iio/adc/Makefile b/drivers/iio/adc/Makefile
index 4ef41a7dfac6..61ef600fab99 100644
--- a/drivers/iio/adc/Makefile
+++ b/drivers/iio/adc/Makefile
@@ -107,6 +107,7 @@ obj-$(CONFIG_TI_ADC108S102) += ti-adc108s102.o
 obj-$(CONFIG_TI_ADC128S052) += ti-adc128s052.o
 obj-$(CONFIG_TI_ADC161S626) += ti-adc161s626.o
 obj-$(CONFIG_TI_ADS1015) += ti-ads1015.o
+obj-$(CONFIG_TI_ADS1100) += ti-ads1100.o
 obj-$(CONFIG_TI_ADS7950) += ti-ads7950.o
 obj-$(CONFIG_TI_ADS8344) += ti-ads8344.o
 obj-$(CONFIG_TI_ADS8688) += ti-ads8688.o
diff --git a/drivers/iio/adc/ti-ads1100.c b/drivers/iio/adc/ti-ads1100.c
new file mode 100644
index 000000000000..2189634dccbf
--- /dev/null
+++ b/drivers/iio/adc/ti-ads1100.c
@@ -0,0 +1,442 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * ADS1100 - Texas Instruments Analog-to-Digital Converter
+ *
+ * Copyright (c) 2023, Topic Embedded Products
+ *
+ * Datasheet: https://www.ti.com/lit/gpn/ads1100
+ * IIO driver for ADS1100 and ADS1000 ADC 16-bit I2C
+ */
+
+#include <linux/bitfield.h>
+#include <linux/bits.h>
+#include <linux/delay.h>
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/i2c.h>
+#include <linux/mutex.h>
+#include <linux/property.h>
+#include <linux/pm_runtime.h>
+#include <linux/regulator/consumer.h>
+#include <linux/units.h>
+
+#include <linux/iio/iio.h>
+#include <linux/iio/types.h>
+
+/* The ADS1100 has a single byte config register */
+
+/* Conversion in progress bit */
+#define ADS1100_CFG_ST_BSY	BIT(7)
+/* Single conversion bit */
+#define ADS1100_CFG_SC		BIT(4)
+/* Data rate */
+#define ADS1100_DR_MASK		GENMASK(3, 2)
+/* Gain */
+#define ADS1100_PGA_MASK	GENMASK(1, 0)
+
+#define ADS1100_CONTINUOUS	0
+#define	ADS1100_SINGLESHOT	ADS1100_CFG_SC
+
+#define ADS1100_SLEEP_DELAY_MS	2000
+
+static const int ads1100_data_rate[] = {128, 32, 16, 8};
+static const int ads1100_data_rate_bits[] = {12, 14, 15, 16};
+
+struct ads1100_data {
+	struct i2c_client *client;
+	struct regulator *reg_vdd;
+	struct mutex lock;
+	int scale_avail[2 * 4]; /* 4 gain settings */
+	u8 config;
+	bool supports_data_rate; /* Only the ADS1100 can select the rate */
+};
+
+static const struct iio_chan_spec ads1100_channel = {
+	.type = IIO_VOLTAGE,
+	.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),
+	.info_mask_shared_by_all =
+				BIT(IIO_CHAN_INFO_SCALE) |
+				BIT(IIO_CHAN_INFO_SAMP_FREQ),
+	.info_mask_shared_by_all_available =
+				BIT(IIO_CHAN_INFO_SCALE) |
+				BIT(IIO_CHAN_INFO_SAMP_FREQ),
+	.scan_type = {
+		.sign = 's',
+		.realbits = 16,
+		.storagebits = 16,
+		.endianness = IIO_CPU,
+	},
+	.datasheet_name = "AIN",
+};
+
+static int ads1100_set_config_bits(struct ads1100_data *data, u8 mask, u8 value)
+{
+	int ret;
+	u8 config = (data->config & ~mask) | (value & mask);
+
+	if (data->config == config)
+		return 0; /* Already done */
+
+	ret = i2c_master_send(data->client, &config, 1);
+	if (ret < 0)
+		return ret;
+
+	data->config = config;
+	return 0;
+};
+
+static int ads1100_data_bits(struct ads1100_data *data)
+{
+	return ads1100_data_rate_bits[FIELD_GET(ADS1100_DR_MASK, data->config)];
+}
+
+static int ads1100_get_adc_result(struct ads1100_data *data, int chan, int *val)
+{
+	int ret;
+	__be16 buffer;
+	s16 value;
+
+	if (chan != 0)
+		return -EINVAL;
+
+	ret = pm_runtime_resume_and_get(&data->client->dev);
+	if (ret < 0)
+		return ret;
+
+	ret = i2c_master_recv(data->client, (char *)&buffer, sizeof(buffer));
+
+	pm_runtime_mark_last_busy(&data->client->dev);
+	pm_runtime_put_autosuspend(&data->client->dev);
+
+	if (ret < 0) {
+		dev_err(&data->client->dev, "I2C read fail: %d\n", ret);
+		return ret;
+	}
+
+	/* Value is always 16-bit 2's complement */
+	value = be16_to_cpu(buffer);
+	/* Shift result to compensate for bit resolution vs. sample rate */
+	value <<= 16 - ads1100_data_bits(data);
+	*val = sign_extend32(value, 15);
+
+	return 0;
+}
+
+static int ads1100_set_scale(struct ads1100_data *data, int val, int val2)
+{
+	int microvolts;
+	int gain;
+	int regval;
+
+	/* With Vdd between 2.7 and 5V, the scale is always below 1 */
+	if (val)
+		return -EINVAL;
+
+	if (!val2)
+		return -EINVAL;
+
+	microvolts = regulator_get_voltage(data->reg_vdd);
+	/*
+	 * val2 is in 'micro' units, n = val2 / 1000000
+	 * result must be millivolts, d = microvolts / 1000
+	 * the full-scale value is d/n, corresponds to 2^15,
+	 * hence the gain = (d / n) >> 15, factoring out the 1000 and moving the
+	 * bitshift so everything fits in 32-bits yields this formula.
+	 */
+	gain = ((microvolts + BIT(14)) >> 15) * 1000 / val2;
+	if (gain <= 0 || gain > 8)
+		return -EINVAL;
+
+	regval = ffs(gain) - 1;
+	ads1100_set_config_bits(data, ADS1100_PGA_MASK, regval);
+	return 0;
+}
+
+static int ads1100_set_data_rate(struct ads1100_data *data, int chan, int rate)
+{
+	unsigned int i;
+	unsigned int size;
+
+	size = data->supports_data_rate ? ARRAY_SIZE(ads1100_data_rate) : 1;
+	for (i = 0; i < size; i++) {
+		if (ads1100_data_rate[i] == rate)
+			return ads1100_set_config_bits(
+					data, ADS1100_DR_MASK,
+					FIELD_PREP(ADS1100_DR_MASK, i));
+	}
+
+	return -EINVAL;
+}
+
+static int ads1100_get_vdd_millivolts(struct ads1100_data *data)
+{
+	return regulator_get_voltage(data->reg_vdd) / (MICRO / MILLI);
+}
+
+static void ads1100_calc_scale_avail(struct ads1100_data *data)
+{
+	int millivolts = ads1100_get_vdd_millivolts(data);
+	unsigned int i;
+
+	for (i = 0; i < ARRAY_SIZE(data->scale_avail) / 2; i++) {
+		data->scale_avail[i * 2 + 0] = millivolts;
+		data->scale_avail[i * 2 + 1] = 15 + i;
+	}
+}
+
+static int ads1100_read_avail(struct iio_dev *indio_dev,
+			      struct iio_chan_spec const *chan,
+			      const int **vals, int *type, int *length,
+			      long mask)
+{
+	struct ads1100_data *data = iio_priv(indio_dev);
+
+	if (chan->type != IIO_VOLTAGE)
+		return -EINVAL;
+
+	switch (mask) {
+	case IIO_CHAN_INFO_SAMP_FREQ:
+		*type = IIO_VAL_INT;
+		*vals = ads1100_data_rate;
+		if (data->supports_data_rate)
+			*length = ARRAY_SIZE(ads1100_data_rate);
+		else
+			*length = 1;
+		return IIO_AVAIL_LIST;
+	case IIO_CHAN_INFO_SCALE:
+		*type = IIO_VAL_FRACTIONAL_LOG2;
+		*vals = data->scale_avail;
+		*length = ARRAY_SIZE(data->scale_avail);
+		return IIO_AVAIL_LIST;
+	default:
+		return -EINVAL;
+	}
+}
+
+static int ads1100_read_raw(struct iio_dev *indio_dev,
+			    struct iio_chan_spec const *chan, int *val,
+			    int *val2, long mask)
+{
+	int ret;
+	struct ads1100_data *data = iio_priv(indio_dev);
+
+	mutex_lock(&data->lock);
+	switch (mask) {
+	case IIO_CHAN_INFO_RAW:
+		ret = iio_device_claim_direct_mode(indio_dev);
+		if (ret)
+			break;
+
+		ret = ads1100_get_adc_result(data, chan->address, val);
+		if (ret >= 0)
+			ret = IIO_VAL_INT;
+		iio_device_release_direct_mode(indio_dev);
+		break;
+	case IIO_CHAN_INFO_SCALE:
+		/* full-scale is the supply voltage in millivolts */
+		*val = ads1100_get_vdd_millivolts(data);
+		*val2 = 15 + FIELD_GET(ADS1100_PGA_MASK, data->config);
+		ret = IIO_VAL_FRACTIONAL_LOG2;
+		break;
+	case IIO_CHAN_INFO_SAMP_FREQ:
+		*val = ads1100_data_rate[FIELD_GET(ADS1100_DR_MASK,
+						   data->config)];
+		ret = IIO_VAL_INT;
+		break;
+	default:
+		ret = -EINVAL;
+		break;
+	}
+	mutex_unlock(&data->lock);
+
+	return ret;
+}
+
+static int ads1100_write_raw(struct iio_dev *indio_dev,
+			     struct iio_chan_spec const *chan, int val,
+			     int val2, long mask)
+{
+	struct ads1100_data *data = iio_priv(indio_dev);
+	int ret;
+
+	mutex_lock(&data->lock);
+	switch (mask) {
+	case IIO_CHAN_INFO_SCALE:
+		ret = ads1100_set_scale(data, val, val2);
+		break;
+	case IIO_CHAN_INFO_SAMP_FREQ:
+		ret = ads1100_set_data_rate(data, chan->address, val);
+		break;
+	default:
+		ret = -EINVAL;
+		break;
+	}
+	mutex_unlock(&data->lock);
+
+	return ret;
+}
+
+static const struct iio_info ads1100_info = {
+	.read_avail	= ads1100_read_avail,
+	.read_raw	= ads1100_read_raw,
+	.write_raw	= ads1100_write_raw,
+};
+
+static int ads1100_setup(struct ads1100_data *data)
+{
+	int ret;
+	u8 buffer[3];
+
+	/* Setup continuous sampling mode at 8sps */
+	buffer[0] = ADS1100_DR_MASK | ADS1100_CONTINUOUS;
+	ret = i2c_master_send(data->client, buffer, 1);
+	if (ret < 0)
+		return ret;
+
+	ret = i2c_master_recv(data->client, buffer, sizeof(buffer));
+	if (ret < 0)
+		return ret;
+
+	/* Config register returned in third byte, strip away the busy status */
+	data->config = buffer[2] & ~ADS1100_CFG_ST_BSY;
+
+	/* Detect the sample rate capability by checking the DR bits */
+	data->supports_data_rate = FIELD_GET(ADS1100_DR_MASK, buffer[2]) != 0;
+
+	return 0;
+}
+
+static void ads1100_reg_disable(void *reg)
+{
+	regulator_disable(reg);
+}
+
+static void ads1100_disable_continuous(void *data)
+{
+	ads1100_set_config_bits(data, ADS1100_CFG_SC, ADS1100_SINGLESHOT);
+}
+
+static int ads1100_probe(struct i2c_client *client)
+{
+	struct iio_dev *indio_dev;
+	struct ads1100_data *data;
+	struct device *dev = &client->dev;
+	int ret;
+
+	indio_dev = devm_iio_device_alloc(dev, sizeof(*data));
+	if (!indio_dev)
+		return -ENOMEM;
+
+	data = iio_priv(indio_dev);
+	dev_set_drvdata(dev, data);
+	data->client = client;
+	mutex_init(&data->lock);
+
+	indio_dev->name = "ads1100";
+	indio_dev->modes = INDIO_DIRECT_MODE;
+	indio_dev->channels = &ads1100_channel;
+	indio_dev->num_channels = 1;
+	indio_dev->info = &ads1100_info;
+
+	data->reg_vdd = devm_regulator_get(dev, "vdd");
+	if (IS_ERR(data->reg_vdd))
+		return dev_err_probe(dev, PTR_ERR(data->reg_vdd),
+				     "Failed to get vdd regulator\n");
+
+	ret = regulator_enable(data->reg_vdd);
+	if (ret < 0)
+		return dev_err_probe(dev, PTR_ERR(data->reg_vdd),
+				     "Failed to enable vdd regulator\n");
+
+	ret = devm_add_action_or_reset(dev, ads1100_reg_disable, data->reg_vdd);
+	if (ret)
+		return ret;
+
+	ret = ads1100_setup(data);
+	if (ret)
+		return dev_err_probe(dev, ret,
+				     "Failed to communicate with device\n");
+
+	ret = devm_add_action_or_reset(dev, ads1100_disable_continuous, data);
+	if (ret)
+		return ret;
+
+	ads1100_calc_scale_avail(data);
+
+	pm_runtime_set_autosuspend_delay(dev, ADS1100_SLEEP_DELAY_MS);
+	pm_runtime_use_autosuspend(dev);
+	pm_runtime_set_active(dev);
+	ret = devm_pm_runtime_enable(dev);
+	if (ret)
+		return dev_err_probe(dev, ret, "Failed to enable pm_runtime\n");
+
+	ret = devm_iio_device_register(dev, indio_dev);
+	if (ret)
+		return dev_err_probe(dev, ret,
+				     "Failed to register IIO device\n");
+
+	return 0;
+}
+
+static int ads1100_runtime_suspend(struct device *dev)
+{
+	struct ads1100_data *data = dev_get_drvdata(dev);
+
+	ads1100_set_config_bits(data, ADS1100_CFG_SC, ADS1100_SINGLESHOT);
+	regulator_disable(data->reg_vdd);
+
+	return 0;
+}
+
+static int ads1100_runtime_resume(struct device *dev)
+{
+	struct ads1100_data *data = dev_get_drvdata(dev);
+	int ret;
+
+	ret = regulator_enable(data->reg_vdd);
+	if (ret) {
+		dev_err(&data->client->dev, "Failed to enable Vdd\n");
+		return ret;
+	}
+
+	/*
+	 * We'll always change the mode bit in the config register, so there is
+	 * no need here to "force" a write to the config register. If the device
+	 * has been power-cycled, we'll re-write its config register now.
+	 */
+	return ads1100_set_config_bits(data, ADS1100_CFG_SC, ADS1100_CONTINUOUS);
+}
+
+static DEFINE_RUNTIME_DEV_PM_OPS(ads1100_pm_ops,
+				 ads1100_runtime_suspend,
+				 ads1100_runtime_resume,
+				 NULL);
+
+static const struct i2c_device_id ads1100_id[] = {
+	{ "ads1100" },
+	{ "ads1000" },
+	{}
+};
+MODULE_DEVICE_TABLE(i2c, ads1100_id);
+
+static const struct of_device_id ads1100_of_match[] = {
+	{ .compatible = "ti,ads1100" },
+	{ .compatible = "ti,ads1000" },
+	{}
+};
+MODULE_DEVICE_TABLE(of, ads1100_of_match);
+
+static struct i2c_driver ads1100_driver = {
+	.driver = {
+		.name = "ads1100",
+		.of_match_table = ads1100_of_match,
+		.pm = pm_ptr(&ads1100_pm_ops),
+	},
+	.probe_new	= ads1100_probe,
+	.id_table	= ads1100_id,
+};
+module_i2c_driver(ads1100_driver);
+
+MODULE_AUTHOR("Mike Looijmans <mike.looijmans@topic.nl>");
+MODULE_DESCRIPTION("Texas Instruments ADS1100 ADC driver");
+MODULE_LICENSE("GPL");
-- 
2.17.1


Met vriendelijke groet / kind regards,

Mike Looijmans
System Expert


TOPIC Embedded Products B.V.
Materiaalweg 4, 5681 RJ Best
The Netherlands

T: +31 (0) 499 33 69 69
E: mike.looijmans@topicproducts.com
W: www.topic.nl

Please consider the environment before printing this e-mail

Re: [PATCH v4 2/2] iio: adc: Add TI ADS1100 and ADS1000

[Andy Shevchenko]

On Mon, Mar 06, 2023 at 02:13:12PM +0100, Mike Looijmans wrote:
> The ADS1100 is a 16-bit ADC (at 8 samples per second).
> The ADS1000 is similar, but has a fixed data rate.

...

> +	/* Value is always 16-bit 2's complement */
> +	value = be16_to_cpu(buffer);

+ Blank line?

> +	/* Shift result to compensate for bit resolution vs. sample rate */
> +	value <<= 16 - ads1100_data_bits(data);

+ Blank line?

> +	*val = sign_extend32(value, 15);

...

> +	microvolts = regulator_get_voltage(data->reg_vdd);
> +	/*
> +	 * val2 is in 'micro' units, n = val2 / 1000000
> +	 * result must be millivolts, d = microvolts / 1000
> +	 * the full-scale value is d/n, corresponds to 2^15,
> +	 * hence the gain = (d / n) >> 15, factoring out the 1000 and moving the
> +	 * bitshift so everything fits in 32-bits yields this formula.
> +	 */
> +	gain = ((microvolts + BIT(14)) >> 15) * 1000 / val2;

Perhaps adding MICROVOLT_PER_MILLIVOLT (to units.h) and use it here?

Besides that it's seems like

	microvolts = regulator_get_voltage(data->reg_vdd);
	gain = DIV_ROUNDUP_CLOSEST(microvolts, BIT(15)) *
	       MICROVOLT_PER_MILLIVOLT / val2;

> +	if (gain <= 0 || gain > 8)
> +		return -EINVAL;

As I commented out in the previous discussion (please, give a chance to the
reviewers to answer before issuing a new version of the series) this better
to be

	if (gain < BIT(0) || gain > BIT(3))

which will show the nature of power of two implicitly.

> +	regval = ffs(gain) - 1;
> +	ads1100_set_config_bits(data, ADS1100_PGA_MASK, regval);

Can be unified in one line.

> +	return 0;
> +}

...

> +			return ads1100_set_config_bits(
> +					data, ADS1100_DR_MASK,
> +					FIELD_PREP(ADS1100_DR_MASK, i));

Wrong indentation.
Please, check all your code for this kind of issues.

-- 
With Best Regards,
Andy Shevchenko

Re: [PATCH v4 2/2] iio: adc: Add TI ADS1100 and ADS1000

[Mike Looijmans]

Met vriendelijke groet / kind regards,

Mike Looijmans
System Expert


TOPIC Embedded Products B.V.
Materiaalweg 4, 5681 RJ Best
The Netherlands

T: +31 (0) 499 33 69 69
E: mike.looijmans@topicproducts.com
W: www.topic.nl

Please consider the environment before printing this e-mail
On 06-03-2023 14:29, Andy Shevchenko wrote:
> On Mon, Mar 06, 2023 at 02:13:12PM +0100, Mike Looijmans wrote:
>> The ADS1100 is a 16-bit ADC (at 8 samples per second).
>> The ADS1000 is similar, but has a fixed data rate.
> ...
>
>> +	microvolts = regulator_get_voltage(data->reg_vdd);
>> +	/*
>> +	 * val2 is in 'micro' units, n = val2 / 1000000
>> +	 * result must be millivolts, d = microvolts / 1000
>> +	 * the full-scale value is d/n, corresponds to 2^15,
>> +	 * hence the gain = (d / n) >> 15, factoring out the 1000 and moving the
>> +	 * bitshift so everything fits in 32-bits yields this formula.
>> +	 */
>> +	gain = ((microvolts + BIT(14)) >> 15) * 1000 / val2;
> Perhaps adding MICROVOLT_PER_MILLIVOLT (to units.h) and use it here?

Would that require a separate patch?

I fear that would get feedback like "why not MICROCOULOB_PER_MILLICOULOMB".

If I fill in the equation then that "1000" is actually 
MICROVOLT_PER_MICROVOLT_PER_MILLIVOLT, which would evaluate to simply 
"MILLIVOLT".


>
> Besides that it's seems like
>
> 	microvolts = regulator_get_voltage(data->reg_vdd);
> 	gain = DIV_ROUNDUP_CLOSEST(microvolts, BIT(15)) *
> 	       MICROVOLT_PER_MILLIVOLT / val2;

Yeah, the DIV_ROUNDUP_CLOSEST is more readable.


>> +	if (gain <= 0 || gain > 8)
>> +		return -EINVAL;
> As I commented out in the previous discussion (please, give a chance to the
> reviewers to answer before issuing a new version of the series) this better
> to be
>
> 	if (gain < BIT(0) || gain > BIT(3))
>
> which will show the nature of power of two implicitly.
>
>> +	regval = ffs(gain) - 1;
>> +	ads1100_set_config_bits(data, ADS1100_PGA_MASK, regval);
> Can be unified in one line.

Combining it all, I'd arrive at this code:

     gain = DIV_ROUNDUP_CLOSEST(microvolts, BIT(15)) * MILLI / val2;
     if (gain < BIT(0) || gain > BIT(3))
         return -EINVAL;

     ads1100_set_config_bits(data, ADS1100_PGA_MASK, ffs(gain) - 1);


>> +	return 0;
>> +}
> ...
>
>> +			return ads1100_set_config_bits(
>> +					data, ADS1100_DR_MASK,
>> +					FIELD_PREP(ADS1100_DR_MASK, i));
> Wrong indentation.
> Please, check all your code for this kind of issues.
>
I always run it through checkpatch.pl but that didn't report on this 
indentation.

A bit of digging in the scripts directory yields "Lindent". Feeding my 
file to that indeed changes those lines (and some others too). I'll run 
my next patch through that.

-- 
Mike Looijmans

Re: [PATCH v4 2/2] iio: adc: Add TI ADS1100 and ADS1000

[Andy Shevchenko]

On Mon, Mar 06, 2023 at 03:44:23PM +0100, Mike Looijmans wrote:
> On 06-03-2023 14:29, Andy Shevchenko wrote:

...

> Combining it all, I'd arrive at this code:
> 
>     gain = DIV_ROUNDUP_CLOSEST(microvolts, BIT(15)) * MILLI / val2;
>     if (gain < BIT(0) || gain > BIT(3))
>         return -EINVAL;
> 
>     ads1100_set_config_bits(data, ADS1100_PGA_MASK, ffs(gain) - 1);

Fine by me.

...

> > > +			return ads1100_set_config_bits(
> > > +					data, ADS1100_DR_MASK,
> > > +					FIELD_PREP(ADS1100_DR_MASK, i));
> > Wrong indentation.
> > Please, check all your code for this kind of issues.
> > 
> I always run it through checkpatch.pl but that didn't report on this
> indentation.

Checkpatch is:

1) not comprehensive;
2) not must-to-follow;

tool.

Use your common sense. You have a lot of room on the previous line at least
for 'data'. Trailing opening ( is not good indentation. But sometimes might
be unavoidable.

> A bit of digging in the scripts directory yields "Lindent". Feeding my file
> to that indeed changes those lines (and some others too). I'll run my next
> patch through that.

If it will look nice, why not?

-- 
With Best Regards,
Andy Shevchenko