[PATCH 0/3] Support ROHM BD79703 DAC

[PATCH 0/3] Support ROHM BD79703 DAC

[Matti Vaittinen]

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Add support for the ROHM BD79703 DAC

The ROHM BD79703 DAC is a 6-channel 8-bit digital to analog converter
which can be controlled over SPI bus. This series adds support for
controlling the analog channels via IIO direct mode.

Matti Vaittinen (3):
  dt-bindings: Add ROHM BD79703
  iio: dac: Support ROHM BD79703 DAC
  MAINTAINERS: Add maintainer for ROHM BD79703

 .../bindings/iio/dac/rohm,bd79703.yaml        |  61 +++++++
 MAINTAINERS                                   |   5 +
 drivers/iio/dac/Kconfig                       |   8 +
 drivers/iio/dac/Makefile                      |   1 +
 drivers/iio/dac/rohm-bd79703.c                | 162 ++++++++++++++++++
 5 files changed, 237 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/iio/dac/rohm,bd79703.yaml
 create mode 100644 drivers/iio/dac/rohm-bd79703.c


base-commit: 4d112ebd02d10faf202aa8335b06de0aca8b536b
-- 
2.47.0


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[PATCH 1/3] dt-bindings: Add ROHM BD79703

[Matti Vaittinen]

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The ROHM BD79703 is a 8-bit, 6 channel DAC.

Describe the dt-bindings.

Signed-off-by: Matti Vaittinen <mazziesaccount@gmail.com>
---
 .../bindings/iio/dac/rohm,bd79703.yaml        | 61 +++++++++++++++++++
 1 file changed, 61 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/iio/dac/rohm,bd79703.yaml

diff --git a/Documentation/devicetree/bindings/iio/dac/rohm,bd79703.yaml b/Documentation/devicetree/bindings/iio/dac/rohm,bd79703.yaml
new file mode 100644
index 000000000000..c51b4037fd0d
--- /dev/null
+++ b/Documentation/devicetree/bindings/iio/dac/rohm,bd79703.yaml
@@ -0,0 +1,61 @@
+# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
+# Copyright 2024 ROHM Semiconductor.
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/iio/dac/rohm,bd79703.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: ROHM BD79703 DAC device driver
+
+maintainers:
+  - Matti Vaittinen <mazziesaccount@gmail.com>
+
+description: |
+  The ROHM BD79703 is a 6 channel, 8-bit DAC.
+  Datasheet can be found here:
+  https://fscdn.rohm.com/en/products/databook/datasheet/ic/data_converter/dac/bd79702fv-lb_bd79703fv-lb-e.pdf
+
+properties:
+  compatible:
+    const: rohm,bd79703
+
+  reg:
+    maxItems: 1
+
+  spi-max-frequency:
+    maximum: 30000000
+
+  vfs-supply:
+    description:
+      The regulator to use as a full scale voltage. The voltage should be between 2.7V .. VCC
+
+  vcc-supply:
+    description:
+      The regulator supplying the operating voltage. Should be between 2.7V ... 5.5V
+
+required:
+  - compatible
+  - reg
+  - spi-max-frequency
+  - vfs-supply
+  - vcc-supply
+
+allOf:
+  - $ref: /schemas/spi/spi-peripheral-props.yaml#
+
+additionalProperties: false
+
+examples:
+  - |
+    spi {
+        #address-cells = <1>;
+        #size-cells = <0>;
+        dac@0 {
+            compatible = "rohm,bd79703";
+            reg = <0>;
+            spi-max-frequency = <30000000>;
+            vcc-supply = <&vcc>;
+            vfs-supply = <&vref>;
+        };
+    };
+...
-- 
2.47.0


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[PATCH 2/3] iio: dac: Support ROHM BD79703 DAC

[Matti Vaittinen]

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The ROHM BD79703 is a 6 channel digital to analog converter.

Based on the data-sheet examples the hardware would support setting the
DAC word without changing the actual output. The data-sheet is not too
specific on how the enabling the output of new voltage set by DAC
should be done - hence this is not implemented by the driver.

The BD79703 would also support two specific "PULL_DOWN" modes. These
aren't currently supported by the driver either.

Add a very basic support for controlling the channel outputs one-by-one.

Signed-off-by: Matti Vaittinen <mazziesaccount@gmail.com>
---
 drivers/iio/dac/Kconfig        |   8 ++
 drivers/iio/dac/Makefile       |   1 +
 drivers/iio/dac/rohm-bd79703.c | 162 +++++++++++++++++++++++++++++++++
 3 files changed, 171 insertions(+)
 create mode 100644 drivers/iio/dac/rohm-bd79703.c

diff --git a/drivers/iio/dac/Kconfig b/drivers/iio/dac/Kconfig
index 4cde34e8c8e3..5690a37267d8 100644
--- a/drivers/iio/dac/Kconfig
+++ b/drivers/iio/dac/Kconfig
@@ -348,6 +348,14 @@ config AD8801
 	  To compile this driver as a module choose M here: the module will be called
 	  ad8801.
 
+config BD79703
+	tristate "ROHM Semiconductor BD79703 DAC driver"
+	depends on SPI
+	select REGMAP_SPI
+	help
+	  Say yes here to build support for ROHM Semiconductor BD79703 Digital
+	  to Analog Converter (DAC).
+
 config CIO_DAC
 	tristate "Measurement Computing CIO-DAC IIO driver"
 	depends on X86 && (ISA_BUS || PC104)
diff --git a/drivers/iio/dac/Makefile b/drivers/iio/dac/Makefile
index 414c152be779..8dd6cce81ed1 100644
--- a/drivers/iio/dac/Makefile
+++ b/drivers/iio/dac/Makefile
@@ -34,6 +34,7 @@ obj-$(CONFIG_AD8460) += ad8460.o
 obj-$(CONFIG_AD8801) += ad8801.o
 obj-$(CONFIG_AD9739A) += ad9739a.o
 obj-$(CONFIG_ADI_AXI_DAC) += adi-axi-dac.o
+obj-$(CONFIG_BD79703) += rohm-bd79703.o
 obj-$(CONFIG_CIO_DAC) += cio-dac.o
 obj-$(CONFIG_DPOT_DAC) += dpot-dac.o
 obj-$(CONFIG_DS4424) += ds4424.o
diff --git a/drivers/iio/dac/rohm-bd79703.c b/drivers/iio/dac/rohm-bd79703.c
new file mode 100644
index 000000000000..a3df31d81b7c
--- /dev/null
+++ b/drivers/iio/dac/rohm-bd79703.c
@@ -0,0 +1,162 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * BD79703 ROHM Digital to Analog converter
+ *
+ * Copyright (c) 2024, ROHM Semiconductor.
+ */
+
+#include <linux/bits.h>
+#include <linux/device.h>
+#include <linux/module.h>
+#include <linux/regmap.h>
+#include <linux/regulator/consumer.h>
+#include <linux/spi/spi.h>
+#include <linux/iio/iio.h>
+
+#define BD79703_MAX_REGISTER 0xf
+#define BD79703_DAC_BITS 8
+#define BD79703_REG_OUT_ALL GENMASK(2, 0)
+
+/*
+ * The BD79703 uses 12-bit SPI commands. First four bits (high bits) define
+ * channel(s) which are operated on, and also the mode. The mode can be to set
+ * a DAC word only, or set DAC word and output. The data-sheet is not very
+ * specific on how a previously set DAC word can be 'taken in to use'. Thus
+ * this driver only uses the 'set DAC and output it' -mode.
+ *
+ * The BD79703 latches last 12-bits when the chip-select is toggled. Thus we
+ * can use 16-bit transfers which should be widely supported. To simplify this
+ * further, we treat the last 8 bits as a value, and first 8 bits as an
+ * address. This allows us to separate channels/mode by address and treat the
+ * 8-bit register value as DAC word. The highest 4 bits of address will be
+ * discarded when the transfer is latched.
+ */
+static const struct regmap_config bd79703_regmap_config = {
+	.reg_bits = 8,
+	.val_bits = 8,
+	.max_register = BD79703_MAX_REGISTER,
+	.cache_type = REGCACHE_RBTREE,
+};
+
+struct bd79703_data {
+	struct regmap *regmap;
+	int vfs;
+};
+
+static int bd79703_read_raw(struct iio_dev *idev,
+			    struct iio_chan_spec const *chan, int *val,
+			    int *val2, long mask)
+{
+	struct bd79703_data *data = iio_priv(idev);
+
+	if (mask != IIO_CHAN_INFO_SCALE)
+		return -EINVAL;
+
+	*val = data->vfs / 1000;
+	*val2 = BD79703_DAC_BITS;
+
+	return IIO_VAL_FRACTIONAL_LOG2;
+}
+
+static int bd79703_write_raw(struct iio_dev *idev,
+			     struct iio_chan_spec const *chan, int val,
+			     int val2, long mask)
+{
+	struct bd79703_data *data = iio_priv(idev);
+
+	if (val < 0 || val >= 1 << BD79703_DAC_BITS)
+		return -EINVAL;
+
+	return regmap_write(data->regmap, chan->channel + 1, val);
+};
+
+static const struct iio_info bd79703_info = {
+	.read_raw = bd79703_read_raw,
+	.write_raw = bd79703_write_raw,
+};
+
+#define BD79703_CHAN(_chan) {					\
+	.type = IIO_VOLTAGE,					\
+	.indexed = 1,						\
+	.output = 1,						\
+	.channel = (_chan),					\
+	.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),		\
+	.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE),	\
+	.address = (_chan),					\
+}
+
+static const struct iio_chan_spec bd79703_channels[] = {
+	BD79703_CHAN(0),
+	BD79703_CHAN(1),
+	BD79703_CHAN(2),
+	BD79703_CHAN(3),
+	BD79703_CHAN(4),
+	BD79703_CHAN(5),
+};
+
+static int bd79703_probe(struct spi_device *spi)
+{
+	struct device *dev = &spi->dev;
+	struct bd79703_data *data;
+	struct iio_dev *idev;
+	int ret;
+
+	idev = devm_iio_device_alloc(dev, sizeof(*data));
+	if (!idev)
+		return -ENOMEM;
+
+	data = iio_priv(idev);
+
+	data->regmap = devm_regmap_init_spi(spi, &bd79703_regmap_config);
+	if (IS_ERR(data->regmap))
+		return dev_err_probe(dev, PTR_ERR(data->regmap),
+				     "Failed to initialize Regmap\n");
+
+	ret = devm_regulator_get_enable(dev, "vcc");
+	if (ret)
+		return dev_err_probe(dev, ret, "Failed to enable VCC\n");
+
+	ret = devm_regulator_get_enable_read_voltage(dev, "vfs");
+	if (ret < 0)
+		return dev_err_probe(dev, ret, "Failed to get Vfs\n");
+
+	data->vfs = ret;
+	idev->channels = bd79703_channels;
+	idev->num_channels = ARRAY_SIZE(bd79703_channels);
+	idev->modes = INDIO_DIRECT_MODE;
+	idev->info = &bd79703_info;
+	idev->name = "bd79703";
+
+	/* Initialize all to output zero */
+	ret = regmap_write(data->regmap, BD79703_REG_OUT_ALL, 0);
+	if (ret)
+		return ret;
+
+	return devm_iio_device_register(dev, idev);
+}
+
+static const struct spi_device_id bd79703_id[] = {
+	{ "bd79703", },
+	{}
+};
+MODULE_DEVICE_TABLE(spi, bd79703_id);
+
+static const struct of_device_id bd79703_of_match[] = {
+	{ .compatible = "rohm,bd79703", },
+	{ }
+};
+MODULE_DEVICE_TABLE(of, bd79703_of_match);
+
+static struct spi_driver bd79703_driver = {
+	.driver = {
+		.name = "bd79703",
+		.of_match_table = bd79703_of_match,
+	},
+	.probe = bd79703_probe,
+	.id_table = bd79703_id,
+};
+module_spi_driver(bd79703_driver);
+
+MODULE_AUTHOR("Matti Vaittinen <mazziesaccount@gmail.com>");
+MODULE_DESCRIPTION("ROHM BD79703 DAC driver");
+MODULE_LICENSE("GPL");
-- 
2.47.0


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[PATCH 3/3] MAINTAINERS: Add maintainer for ROHM BD79703

[Matti Vaittinen]

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Add undersigned as a maintainer for the ROHM BD79703 DAC driver.

Signed-off-by: Matti Vaittinen <mazziesaccount@gmail.com>
---
 MAINTAINERS | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/MAINTAINERS b/MAINTAINERS
index 8e5167443cea..98a3c1e46311 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -20286,6 +20286,11 @@ L:	linux-serial@vger.kernel.org
 S:	Odd Fixes
 F:	drivers/tty/serial/rp2.*
 
+ROHM BD79703 DAC
+M:	Matti Vaittinen <mazziesaccount@gmail.com>
+S:	Supported
+F:	drivers/iio/dac/rohm-bd79703.c
+
 ROHM BD99954 CHARGER IC
 M:	Matti Vaittinen <mazziesaccount@gmail.com>
 S:	Supported
-- 
2.47.0


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Re: [PATCH 2/3] iio: dac: Support ROHM BD79703 DAC

[Jonathan Cameron]

On Thu, 19 Dec 2024 13:39:37 +0200
Matti Vaittinen <mazziesaccount@gmail.com> wrote:

> The ROHM BD79703 is a 6 channel digital to analog converter.
> 
> Based on the data-sheet examples the hardware would support setting the
> DAC word without changing the actual output. The data-sheet is not too
> specific on how the enabling the output of new voltage set by DAC
> should be done - hence this is not implemented by the driver.

I took a quick look and that does seem rather mysterious!
Normally there is either a 'sync' register or pin for setups like this
but no sign of either.  Maybe it's legacy from some other use of the
same silicon.

> 
> The BD79703 would also support two specific "PULL_DOWN" modes. These
> aren't currently supported by the driver either.
> 
> Add a very basic support for controlling the channel outputs one-by-one.
> 
> Signed-off-by: Matti Vaittinen <mazziesaccount@gmail.com>

Short and sweet.  One totally trivial formatting thing I can fix whilst
applying and a passing comment below. will leave this a little while
to see what other feedback it gets and for DT folk to look at the binding.

Jonathan


> diff --git a/drivers/iio/dac/rohm-bd79703.c b/drivers/iio/dac/rohm-bd79703.c
> new file mode 100644
> index 000000000000..a3df31d81b7c
> --- /dev/null
> +++ b/drivers/iio/dac/rohm-bd79703.c
> @@ -0,0 +1,162 @@


> +
> +static int bd79703_probe(struct spi_device *spi)
> +{
> +	struct device *dev = &spi->dev;
> +	struct bd79703_data *data;
> +	struct iio_dev *idev;
> +	int ret;
> +
> +	idev = devm_iio_device_alloc(dev, sizeof(*data));
> +	if (!idev)
> +		return -ENOMEM;
> +
> +	data = iio_priv(idev);
> +
> +	data->regmap = devm_regmap_init_spi(spi, &bd79703_regmap_config);
> +	if (IS_ERR(data->regmap))
> +		return dev_err_probe(dev, PTR_ERR(data->regmap),
> +				     "Failed to initialize Regmap\n");
> +
> +	ret = devm_regulator_get_enable(dev, "vcc");
> +	if (ret)
> +		return dev_err_probe(dev, ret, "Failed to enable VCC\n");
> +
> +	ret = devm_regulator_get_enable_read_voltage(dev, "vfs");
> +	if (ret < 0)
> +		return dev_err_probe(dev, ret, "Failed to get Vfs\n");
> +
> +	data->vfs = ret;
> +	idev->channels = bd79703_channels;
> +	idev->num_channels = ARRAY_SIZE(bd79703_channels);
> +	idev->modes = INDIO_DIRECT_MODE;
> +	idev->info = &bd79703_info;
> +	idev->name = "bd79703";
> +
> +	/* Initialize all to output zero */

I can't remember what we tend to do for defaults but I guess this
is safe enough. Alternative would be start the device with HI impedance
(power down state)

> +	ret = regmap_write(data->regmap, BD79703_REG_OUT_ALL, 0);
> +	if (ret)
> +		return ret;
> +
> +	return devm_iio_device_register(dev, idev);
> +}
> +
> +static const struct spi_device_id bd79703_id[] = {
> +	{ "bd79703", },
> +	{}
	{ }

Keep it consistent. This is the style I prefer though not sure I'll do
a full tidy up of this any time soon. 
> +};
> +MODULE_DEVICE_TABLE(spi, bd79703_id);
> +
> +static const struct of_device_id bd79703_of_match[] = {
> +	{ .compatible = "rohm,bd79703", },
> +	{ }
> +};
> +MODULE_DEVICE_TABLE(of, bd79703_of_match);

Re: [PATCH 1/3] dt-bindings: Add ROHM BD79703

[Conor Dooley]

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On Thu, Dec 19, 2024 at 01:39:11PM +0200, Matti Vaittinen wrote:
> +    spi {
> +        #address-cells = <1>;
> +        #size-cells = <0>;
> +        dac@0 {

nit: should be a blank line before the child node.
Reviewed-by: Conor Dooley <conor.dooley@microchip.com>

Cheers,
Conor.

> +            compatible = "rohm,bd79703";
> +            reg = <0>;
> +            spi-max-frequency = <30000000>;
> +            vcc-supply = <&vcc>;
> +            vfs-supply = <&vref>;
> +        };
> +    };
> +...
> -- 
> 2.47.0
> 



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Re: [PATCH 0/3] Support ROHM BD79703 DAC

[Jonathan Cameron]

On Thu, 19 Dec 2024 13:38:54 +0200
Matti Vaittinen <mazziesaccount@gmail.com> wrote:

> Add support for the ROHM BD79703 DAC
> 
> The ROHM BD79703 DAC is a 6-channel 8-bit digital to analog converter
> which can be controlled over SPI bus. This series adds support for
> controlling the analog channels via IIO direct mode.
Tweaked the two trivial comments from Conor and I and applied.

Pushed out as testing for all the normal reasons plus that this was only
on the list for a day so there may be more reviews! :)

What can I say, it's near Christmas and I was feeling impatient!
> 
> Matti Vaittinen (3):
>   dt-bindings: Add ROHM BD79703
>   iio: dac: Support ROHM BD79703 DAC
>   MAINTAINERS: Add maintainer for ROHM BD79703
> 
>  .../bindings/iio/dac/rohm,bd79703.yaml        |  61 +++++++
>  MAINTAINERS                                   |   5 +
>  drivers/iio/dac/Kconfig                       |   8 +
>  drivers/iio/dac/Makefile                      |   1 +
>  drivers/iio/dac/rohm-bd79703.c                | 162 ++++++++++++++++++
>  5 files changed, 237 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/iio/dac/rohm,bd79703.yaml
>  create mode 100644 drivers/iio/dac/rohm-bd79703.c
> 
> 
> base-commit: 4d112ebd02d10faf202aa8335b06de0aca8b536b

Re: [PATCH 0/3] Support ROHM BD79703 DAC

[Matti Vaittinen]

On 20/12/2024 21:12, Jonathan Cameron wrote:
> On Thu, 19 Dec 2024 13:38:54 +0200
> Matti Vaittinen <mazziesaccount@gmail.com> wrote:
> 
>> Add support for the ROHM BD79703 DAC
>>
>> The ROHM BD79703 DAC is a 6-channel 8-bit digital to analog converter
>> which can be controlled over SPI bus. This series adds support for
>> controlling the analog channels via IIO direct mode.
> Tweaked the two trivial comments from Conor and I and applied.
> 
> Pushed out as testing for all the normal reasons plus that this was only
> on the list for a day so there may be more reviews! :)
> 
> What can I say, it's near Christmas and I was feeling impatient!

Whoah!

I think I received your comments maybe around an hour after sending the 
series. And just couple of days later the series got merged to your 
tree. I'd say this is a new record for drivers I've written! It must be 
the holiday spirits XD

Quite effective! Thanks! ;)

Yours,
	-- Matti