[PATCH v7 1/2] dt-bindings: iio: adc: add max14001

[PATCH v7 1/2] dt-bindings: iio: adc: add max14001

[Kim Seer Paller]

The MAX14001 is a configurable, isolated 10-bit ADC for multi-range
binary inputs.

Signed-off-by: Kim Seer Paller <kimseer.paller@analog.com>
---
V6 -> V7: No changes.
V5 -> V6: Removed tags.
V3 -> V5: Added spaces between prefixes in subject. Fixed MAINTAINERS reference.

 .../bindings/iio/adc/adi,max14001.yaml        | 54 +++++++++++++++++++
 MAINTAINERS                                   |  7 +++
 2 files changed, 61 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/iio/adc/adi,max14001.yaml

diff --git a/Documentation/devicetree/bindings/iio/adc/adi,max14001.yaml b/Documentation/devicetree/bindings/iio/adc/adi,max14001.yaml
new file mode 100644
index 000000000000..9d03c611fca3
--- /dev/null
+++ b/Documentation/devicetree/bindings/iio/adc/adi,max14001.yaml
@@ -0,0 +1,54 @@
+# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
+# Copyright 2023 Analog Devices Inc.
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/iio/adc/adi,max14001.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Analog Devices MAX14001 ADC
+
+maintainers:
+  - Kim Seer Paller <kimseer.paller@analog.com>
+
+description: |
+    Single channel 10 bit ADC with SPI interface. Datasheet
+    can be found here:
+      https://www.analog.com/media/en/technical-documentation/data-sheets/MAX14001-MAX14002.pdf
+
+properties:
+  compatible:
+    enum:
+      - adi,max14001
+
+  reg:
+    maxItems: 1
+
+  spi-max-frequency:
+    maximum: 5000000
+
+  vref-supply:
+    description: Voltage reference to establish input scaling.
+
+required:
+  - compatible
+  - reg
+
+allOf:
+  - $ref: /schemas/spi/spi-peripheral-props.yaml#
+
+unevaluatedProperties: false
+
+examples:
+  - |
+    spi {
+        #address-cells = <1>;
+        #size-cells = <0>;
+
+        adc@0 {
+            compatible = "adi,max14001";
+            reg = <0>;
+            spi-max-frequency = <5000000>;
+            vref-supply = <&vref_reg>;
+        };
+    };
+...
diff --git a/MAINTAINERS b/MAINTAINERS
index f794002a192e..dcea2c31f920 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -12670,6 +12670,13 @@ S:	Maintained
 F:	Documentation/devicetree/bindings/sound/max9860.txt
 F:	sound/soc/codecs/max9860.*
 
+MAX14001 IIO ADC DRIVER
+M:	Kim Seer Paller <kimseer.paller@analog.com>
+L:	linux-iio@vger.kernel.org
+S:	Supported
+W:	https://ez.analog.com/linux-software-drivers
+F:	Documentation/devicetree/bindings/iio/adc/adi,max14001.yaml
+
 MAXBOTIX ULTRASONIC RANGER IIO DRIVER
 M:	Andreas Klinger <ak@it-klinger.de>
 L:	linux-iio@vger.kernel.org

base-commit: 6f449d52b90fdd927fcf9df0388701de6d5381c6
-- 
2.34.1

[PATCH v7 2/2] iio: adc: max14001: New driver

[Kim Seer Paller]

The MAX14001 is configurable, isolated 10-bit ADCs for multi-range
binary inputs.

Signed-off-by: Kim Seer Paller <kimseer.paller@analog.com>
---
V6 -> V7: Swapped ADC external vref source and regulator_get_voltage 
calls. Added forced cast and comment to addressed endian warning.
V5 -> V6: Replaced fixed length assignment with dynamic size 
assignment in xfers struct initialization. Removed .channel 
assignment in max14001_channels definition.
V4 -> V5: No changes.
V3 -> V4: Removed regmap setup, structures, and include.

 MAINTAINERS                |   1 +
 drivers/iio/adc/Kconfig    |  10 ++
 drivers/iio/adc/Makefile   |   1 +
 drivers/iio/adc/max14001.c | 340 +++++++++++++++++++++++++++++++++++++
 4 files changed, 352 insertions(+)
 create mode 100644 drivers/iio/adc/max14001.c

diff --git a/MAINTAINERS b/MAINTAINERS
index dcea2c31f920..b527cf471d7a 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -12676,6 +12676,7 @@ L:	linux-iio@vger.kernel.org
 S:	Supported
 W:	https://ez.analog.com/linux-software-drivers
 F:	Documentation/devicetree/bindings/iio/adc/adi,max14001.yaml
+F:	drivers/iio/adc/max14001.c
 
 MAXBOTIX ULTRASONIC RANGER IIO DRIVER
 M:	Andreas Klinger <ak@it-klinger.de>
diff --git a/drivers/iio/adc/Kconfig b/drivers/iio/adc/Kconfig
index eb2b09ef5d5b..e599d166e98d 100644
--- a/drivers/iio/adc/Kconfig
+++ b/drivers/iio/adc/Kconfig
@@ -706,6 +706,16 @@ config MAX11410
 	  To compile this driver as a module, choose M here: the module will be
 	  called max11410.
 
+config MAX14001
+	tristate "Analog Devices MAX14001 ADC driver"
+	depends on SPI
+	help
+	  Say yes here to build support for Analog Devices MAX14001 Configurable,
+	  Isolated 10-bit ADCs for Multi-Range Binary Inputs.
+
+	  To compile this driver as a module, choose M here: the module will be
+	  called max14001.
+
 config MAX1241
 	tristate "Maxim max1241 ADC driver"
 	depends on SPI_MASTER
diff --git a/drivers/iio/adc/Makefile b/drivers/iio/adc/Makefile
index e07e4a3e6237..9f8964258f03 100644
--- a/drivers/iio/adc/Makefile
+++ b/drivers/iio/adc/Makefile
@@ -65,6 +65,7 @@ obj-$(CONFIG_MAX11100) += max11100.o
 obj-$(CONFIG_MAX1118) += max1118.o
 obj-$(CONFIG_MAX11205) += max11205.o
 obj-$(CONFIG_MAX11410) += max11410.o
+obj-$(CONFIG_MAX14001) += max14001.o
 obj-$(CONFIG_MAX1241) += max1241.o
 obj-$(CONFIG_MAX1363) += max1363.o
 obj-$(CONFIG_MAX9611) += max9611.o
diff --git a/drivers/iio/adc/max14001.c b/drivers/iio/adc/max14001.c
new file mode 100644
index 000000000000..b767cf86c5e3
--- /dev/null
+++ b/drivers/iio/adc/max14001.c
@@ -0,0 +1,340 @@
+// SPDX-License-Identifier: (GPL-2.0-only OR BSD-3-Clause)
+/*
+ * Analog Devices MAX14001 ADC driver
+ *
+ * Copyright 2023 Analog Devices Inc.
+ */
+
+#include <linux/bitfield.h>
+#include <linux/bitrev.h>
+#include <linux/device.h>
+#include <linux/iio/iio.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/mod_devicetable.h>
+#include <linux/property.h>
+#include <linux/regulator/consumer.h>
+#include <linux/spi/spi.h>
+#include <linux/slab.h>
+#include <linux/types.h>
+
+#include <asm/unaligned.h>
+
+/* MAX14001 Registers Address */
+#define MAX14001_ADC			0x00
+#define MAX14001_FADC			0x01
+#define MAX14001_FLAGS			0x02
+#define MAX14001_FLTEN			0x03
+#define MAX14001_THL			0x04
+#define MAX14001_THU			0x05
+#define MAX14001_INRR			0x06
+#define MAX14001_INRT			0x07
+#define MAX14001_INRP			0x08
+#define MAX14001_CFG			0x09
+#define MAX14001_ENBL			0x0A
+#define MAX14001_ACT			0x0B
+#define MAX14001_WEN			0x0C
+
+#define MAX14001_VERIFICATION_REG(x)	((x) + 0x10)
+
+#define MAX14001_CFG_EXRF		BIT(5)
+
+#define MAX14001_ADDR_MASK		GENMASK(15, 11)
+#define MAX14001_DATA_MASK		GENMASK(9, 0)
+#define MAX14001_FILTER_MASK		GENMASK(3, 2)
+
+#define MAX14001_SET_WRITE_BIT		BIT(10)
+#define MAX14001_WRITE_WEN		0x294
+
+struct max14001_state {
+	struct spi_device	*spi;
+	/*
+	 * lock protect against multiple concurrent accesses, RMW sequence, and
+	 * SPI transfer
+	 */
+	struct mutex		lock;
+	int			vref_mv;
+	/*
+	 * DMA (thus cache coherency maintenance) requires the
+	 * transfer buffers to live in their own cache lines.
+	 */
+	__be16			spi_tx_buffer __aligned(IIO_DMA_MINALIGN);
+	__be16			spi_rx_buffer;
+};
+
+static int max14001_read(void *context, unsigned int reg_addr, unsigned int *data)
+{
+	struct max14001_state *st = context;
+	int ret;
+
+	struct spi_transfer xfers[] = {
+		{
+			.tx_buf = &st->spi_tx_buffer,
+			.len = sizeof(st->spi_tx_buffer),
+			.cs_change = 1,
+		}, {
+			.rx_buf = &st->spi_rx_buffer,
+			.len = sizeof(st->spi_rx_buffer),
+		},
+	};
+
+	/*
+	 * Convert transmit buffer to big-endian format and reverse transmit
+	 * buffer to align with the LSB-first input on SDI port.
+	 */
+	st->spi_tx_buffer = cpu_to_be16(bitrev16(FIELD_PREP(MAX14001_ADDR_MASK,
+								reg_addr)));
+
+	ret = spi_sync_transfer(st->spi, xfers, ARRAY_SIZE(xfers));
+	if (ret)
+		return ret;
+
+	/*
+	 * Align received data from the receive buffer, reversing and reordering
+	 * it to match the expected MSB-first format.
+	 */
+	*data = (__force u16)(be16_to_cpu(bitrev16(st->spi_rx_buffer))) &
+							MAX14001_DATA_MASK;
+
+	return 0;
+}
+
+static int max14001_write(void *context, unsigned int reg_addr, unsigned int data)
+{
+	struct max14001_state *st = context;
+
+	/*
+	 * Convert transmit buffer to big-endian format and reverse transmit
+	 * buffer to align with the LSB-first input on SDI port.
+	 */
+	st->spi_tx_buffer = (__force u16)(cpu_to_be16(bitrev16(
+				FIELD_PREP(MAX14001_ADDR_MASK, reg_addr) |
+				FIELD_PREP(MAX14001_SET_WRITE_BIT, 1) |
+				FIELD_PREP(MAX14001_DATA_MASK, data))));
+
+	return spi_write(st->spi, &st->spi_tx_buffer, sizeof(st->spi_tx_buffer));
+}
+
+static int max14001_write_verification_reg(struct max14001_state *st,
+						unsigned int reg_addr)
+{
+	unsigned int reg_data;
+	int ret;
+
+	ret = max14001_read(st, reg_addr, &reg_data);
+	if (ret)
+		return ret;
+
+	return max14001_write(st, MAX14001_VERIFICATION_REG(reg_addr), reg_data);
+}
+
+static int max14001_reg_update(struct max14001_state *st,
+				unsigned int reg_addr,
+				unsigned int mask,
+				unsigned int val)
+{
+	int ret;
+	unsigned int reg_data;
+
+	/* Enable SPI Registers Write */
+	ret = max14001_write(st, MAX14001_WEN, MAX14001_WRITE_WEN);
+	if (ret)
+		return ret;
+
+	ret = max14001_read(st, reg_addr, &reg_data);
+	if (ret)
+		return ret;
+
+	reg_data = FIELD_PREP(mask, val);
+
+	ret = max14001_write(st, reg_addr, reg_data);
+	if (ret)
+		return ret;
+
+	/* Write Verification Register */
+	ret = max14001_write_verification_reg(st, reg_addr);
+	if (ret)
+		return ret;
+
+	/* Disable SPI Registers Write */
+	return max14001_write(st, MAX14001_WEN, 0);
+}
+
+static int max14001_read_raw(struct iio_dev *indio_dev,
+			     struct iio_chan_spec const *chan,
+			     int *val, int *val2, long mask)
+{
+	struct max14001_state *st = iio_priv(indio_dev);
+	unsigned int data;
+	int ret;
+
+	switch (mask) {
+	case IIO_CHAN_INFO_RAW:
+		mutex_lock(&st->lock);
+		ret = max14001_read(st, MAX14001_ADC, &data);
+		mutex_unlock(&st->lock);
+		if (ret < 0)
+			return ret;
+
+		*val = data;
+
+		return IIO_VAL_INT;
+	case IIO_CHAN_INFO_SCALE:
+		*val = st->vref_mv;
+		*val2 = 10;
+
+		return IIO_VAL_FRACTIONAL_LOG2;
+	default:
+		return -EINVAL;
+	}
+}
+
+static const struct iio_info max14001_info = {
+	.read_raw = max14001_read_raw,
+};
+
+static const struct iio_chan_spec max14001_channels[] = {
+	{
+		.type = IIO_VOLTAGE,
+		.info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |
+				      BIT(IIO_CHAN_INFO_SCALE),
+	}
+};
+
+static void max14001_regulator_disable(void *data)
+{
+	struct regulator *reg = data;
+
+	regulator_disable(reg);
+}
+
+static int max14001_init(struct max14001_state *st)
+{
+	int ret;
+
+	/* Enable SPI Registers Write */
+	ret = max14001_write(st, MAX14001_WEN, MAX14001_WRITE_WEN);
+	if (ret)
+		return ret;
+
+	/*
+	 * Reads all registers and writes the values back to their appropriate
+	 * verification registers to clear the Memory Validation fault.
+	 */
+	ret = max14001_write_verification_reg(st, MAX14001_FLTEN);
+	if (ret)
+		return ret;
+
+	ret = max14001_write_verification_reg(st, MAX14001_THL);
+	if (ret)
+		return ret;
+
+	ret = max14001_write_verification_reg(st, MAX14001_THU);
+	if (ret)
+		return ret;
+
+	ret = max14001_write_verification_reg(st, MAX14001_INRR);
+	if (ret)
+		return ret;
+
+	ret = max14001_write_verification_reg(st, MAX14001_INRT);
+	if (ret)
+		return ret;
+
+	ret = max14001_write_verification_reg(st, MAX14001_INRP);
+	if (ret)
+		return ret;
+
+	ret = max14001_write_verification_reg(st, MAX14001_CFG);
+	if (ret)
+		return ret;
+
+	ret = max14001_write_verification_reg(st, MAX14001_ENBL);
+	if (ret)
+		return ret;
+
+	/* Disable SPI Registers Write */
+	return max14001_write(st, MAX14001_WEN, 0);
+}
+
+static int max14001_probe(struct spi_device *spi)
+{
+	struct iio_dev *indio_dev;
+	struct max14001_state *st;
+	struct regulator *vref;
+	struct device *dev = &spi->dev;
+	int ret;
+
+	indio_dev = devm_iio_device_alloc(dev, sizeof(*st));
+	if (!indio_dev)
+		return -ENOMEM;
+
+	st = iio_priv(indio_dev);
+	st->spi = spi;
+
+	indio_dev->name = "max14001";
+	indio_dev->info = &max14001_info;
+	indio_dev->channels = max14001_channels;
+	indio_dev->num_channels = ARRAY_SIZE(max14001_channels);
+	indio_dev->modes = INDIO_DIRECT_MODE;
+
+	ret = max14001_init(st);
+	if (ret)
+		return ret;
+
+	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 regulator");
+
+		/* internal reference */
+		st->vref_mv = 1250;
+	} else {
+		ret = regulator_enable(vref);
+		if (ret)
+			return dev_err_probe(dev, ret,
+					"Failed to enable vref regulators\n");
+
+		ret = devm_add_action_or_reset(dev, max14001_regulator_disable,
+					       vref);
+		if (ret)
+			return ret;
+
+		ret = regulator_get_voltage(vref);
+		if (ret < 0)
+			return dev_err_probe(dev, ret,
+					     "Failed to get vref\n");
+
+		st->vref_mv = ret / 1000;
+
+		/* select external voltage reference source for the ADC */
+		ret = max14001_reg_update(st, MAX14001_CFG,
+					  MAX14001_CFG_EXRF, 1);
+		if (ret < 0)
+			return ret;
+	}
+
+	mutex_init(&st->lock);
+
+	return devm_iio_device_register(dev, indio_dev);
+}
+
+static const struct of_device_id max14001_of_match[] = {
+	{ .compatible = "adi,max14001" },
+	{ }
+};
+MODULE_DEVICE_TABLE(of, max14001_of_match);
+
+static struct spi_driver max14001_driver = {
+	.driver = {
+		.name = "max14001",
+		.of_match_table = max14001_of_match,
+	},
+	.probe = max14001_probe,
+};
+module_spi_driver(max14001_driver);
+
+MODULE_AUTHOR("Kim Seer Paller");
+MODULE_DESCRIPTION("MAX14001 ADC driver");
+MODULE_LICENSE("GPL");
-- 
2.34.1

Re: [PATCH v7 2/2] iio: adc: max14001: New driver

[Andy Shevchenko]

On Tue, Jun 20, 2023 at 4:27 PM Kim Seer Paller
<kimseer.paller@analog.com> wrote:
>
> The MAX14001 is configurable, isolated 10-bit ADCs for multi-range
> binary inputs.

...

> +       /*
> +        * Align received data from the receive buffer, reversing and reordering
> +        * it to match the expected MSB-first format.
> +        */
> +       *data = (__force u16)(be16_to_cpu(bitrev16(st->spi_rx_buffer))) &
> +                                                       MAX14001_DATA_MASK;

Using __force in the C files is somehow stinky.

...

> +       /*
> +        * Convert transmit buffer to big-endian format and reverse transmit
> +        * buffer to align with the LSB-first input on SDI port.
> +        */
> +       st->spi_tx_buffer = (__force u16)(cpu_to_be16(bitrev16(

You have a different type of spi_tx_buffer than u16, don't you?

> +                               FIELD_PREP(MAX14001_ADDR_MASK, reg_addr) |
> +                               FIELD_PREP(MAX14001_SET_WRITE_BIT, 1) |
> +                               FIELD_PREP(MAX14001_DATA_MASK, data))));

...

> +       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 regulator");
> +
> +               /* internal reference */
> +               st->vref_mv = 1250;
> +       } else {
> +               ret = regulator_enable(vref);
> +               if (ret)
> +                       return dev_err_probe(dev, ret,
> +                                       "Failed to enable vref regulators\n");
> +
> +               ret = devm_add_action_or_reset(dev, max14001_regulator_disable,
> +                                              vref);
> +               if (ret)
> +                       return ret;
> +
> +               ret = regulator_get_voltage(vref);
> +               if (ret < 0)
> +                       return dev_err_probe(dev, ret,
> +                                            "Failed to get vref\n");
> +
> +               st->vref_mv = ret / 1000;
> +
> +               /* select external voltage reference source for the ADC */
> +               ret = max14001_reg_update(st, MAX14001_CFG,
> +                                         MAX14001_CFG_EXRF, 1);
> +               if (ret < 0)
> +                       return ret;
> +       }

Now, looking at this code I'm wondering if we may have something like
devm_regulator_get_enable_and_voltage_optional()

But it's another story.


-- 
With Best Regards,
Andy Shevchenko

RE: [PATCH v7 2/2] iio: adc: max14001: New driver

[Paller, Kim Seer]

> -----Original Message-----
> From: Andy Shevchenko <andy.shevchenko@gmail.com>
> Sent: Tuesday, June 20, 2023 11:15 PM
> To: Paller, Kim Seer <KimSeer.Paller@analog.com>
> Cc: jic23@kernel.org; lars@metafoo.de; lgirdwood@gmail.com;
> broonie@kernel.org; Hennerich, Michael <Michael.Hennerich@analog.com>;
> robh@kernel.org; krzysztof.kozlowski@linaro.org; conor+dt@kernel.org; linux-
> iio@vger.kernel.org; linux-kernel@vger.kernel.org; devicetree@vger.kernel.org
> Subject: Re: [PATCH v7 2/2] iio: adc: max14001: New driver
> 
> [External]
> 
> On Tue, Jun 20, 2023 at 4:27 PM Kim Seer Paller
> <kimseer.paller@analog.com> wrote:
> >
> > The MAX14001 is configurable, isolated 10-bit ADCs for multi-range
> > binary inputs.
> 
> ...
> 
> > +       /*
> > +        * Align received data from the receive buffer, reversing and reordering
> > +        * it to match the expected MSB-first format.
> > +        */
> > +       *data = (__force u16)(be16_to_cpu(bitrev16(st->spi_rx_buffer))) &
> > +                                                       MAX14001_DATA_MASK;
> 
> Using __force in the C files is somehow stinky.
> 
> ...
> 
> > +       /*
> > +        * Convert transmit buffer to big-endian format and reverse transmit
> > +        * buffer to align with the LSB-first input on SDI port.
> > +        */
> > +       st->spi_tx_buffer = (__force u16)(cpu_to_be16(bitrev16(
> 
> You have a different type of spi_tx_buffer than u16, don't you?

I have the same type of spi_tx_buffer as u16. 

Other than using force cast, is there any way to resolve the endian warning? I have 
actually swapped the order of bitrev16() and cpu_to_be16/be16_to_cpu() functions. 
I have tested and they also work fine.

Best regards,
Kim Seer Paller

Re: [PATCH v7 2/2] iio: adc: max14001: New driver

[Andy Shevchenko]

On Wed, Jun 21, 2023 at 3:38 AM Paller, Kim Seer
<KimSeer.Paller@analog.com> wrote:
> > From: Andy Shevchenko <andy.shevchenko@gmail.com>
> > Sent: Tuesday, June 20, 2023 11:15 PM
> > On Tue, Jun 20, 2023 at 4:27 PM Kim Seer Paller
> > <kimseer.paller@analog.com> wrote:

...

> > > +       /*
> > > +        * Align received data from the receive buffer, reversing and reordering
> > > +        * it to match the expected MSB-first format.
> > > +        */
> > > +       *data = (__force u16)(be16_to_cpu(bitrev16(st->spi_rx_buffer))) &
> > > +                                                       MAX14001_DATA_MASK;
> >
> > Using __force in the C files is somehow stinky.

...

> > > +       /*
> > > +        * Convert transmit buffer to big-endian format and reverse transmit
> > > +        * buffer to align with the LSB-first input on SDI port.
> > > +        */
> > > +       st->spi_tx_buffer = (__force u16)(cpu_to_be16(bitrev16(
> >
> > You have a different type of spi_tx_buffer than u16, don't you?
>
> I have the same type of spi_tx_buffer as u16.

And you should have __be16.

> Other than using force cast, is there any way to resolve the endian warning? I have
> actually swapped the order of bitrev16() and cpu_to_be16/be16_to_cpu() functions.
> I have tested and they also work fine.

You really have to get it correct on both LE and BE architectures.

-- 
With Best Regards,
Andy Shevchenko

Re: [PATCH v7 1/2] dt-bindings: iio: adc: add max14001

[Krzysztof Kozlowski]

On 20/06/2023 15:26, Kim Seer Paller wrote:
> The MAX14001 is a configurable, isolated 10-bit ADC for multi-range
> binary inputs.
> 
> Signed-off-by: Kim Seer Paller <kimseer.paller@analog.com>
> ---
> V6 -> V7: No changes.

This is a friendly reminder during the review process.

It looks like you received a tag and forgot to add it.

If you do not know the process, here is a short explanation:
Please add Acked-by/Reviewed-by/Tested-by tags when posting new
versions. However, there's no need to repost patches *only* to add the
tags. The upstream maintainer will do that for acks received on the
version they apply.

https://elixir.bootlin.com/linux/v5.17/source/Documentation/process/submitting-patches.rst#L540

If a tag was not added on purpose, please state why and what changed.\


Best regards,
Krzysztof