[PATCH v2 1/2] dt-bindings: iio: dac: add MCP4821

[PATCH v2 1/2] dt-bindings: iio: dac: add MCP4821

[Anshul Dalal]

Adds support for MCP48xx series of DACs.

Datasheet: https://ww1.microchip.com/downloads/en/DeviceDoc/22244B.pdf #MCP48x1
Datasheet: https://ww1.microchip.com/downloads/en/DeviceDoc/20002249B.pdf #MCP48x2
Reviewed-by: Conor Dooley <conor.dooley@microchip.com>
Signed-off-by: Anshul Dalal <anshulusr@gmail.com>

---

Changes for v2:
- Changed order in device table to numerical
- Made vdd_supply required
- Added 'Reviewed-by: Conor Dooley'

Previous versions:
v1: https://lore.kernel.org/lkml/20231117073040.685860-1-anshulusr@gmail.com/
---
 .../bindings/iio/dac/microchip,mcp4821.yaml   | 64 +++++++++++++++++++
 1 file changed, 64 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/iio/dac/microchip,mcp4821.yaml

diff --git a/Documentation/devicetree/bindings/iio/dac/microchip,mcp4821.yaml b/Documentation/devicetree/bindings/iio/dac/microchip,mcp4821.yaml
new file mode 100644
index 000000000000..97da9f9ef450
--- /dev/null
+++ b/Documentation/devicetree/bindings/iio/dac/microchip,mcp4821.yaml
@@ -0,0 +1,64 @@
+# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/iio/dac/microchip,mcp4821.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Microchip MCP4821 and similar DACs
+
+description: |
+  Supports MCP48x1 (single channel) and MCP48x2 (dual channel) series of DACs.
+  Device supports simplex communication over SPI in Mode 0,1 and Mode 1,1.
+
+  +---------+--------------+-------------+
+  | Device  |  Resolution  |   Channels  |
+  |---------|--------------|-------------|
+  | MCP4801 |     8-bit    |      1      |
+  | MCP4802 |     8-bit    |      2      |
+  | MCP4811 |    10-bit    |      1      |
+  | MCP4812 |    10-bit    |      2      |
+  | MCP4821 |    12-bit    |      1      |
+  | MCP4822 |    12-bit    |      2      |
+  +---------+--------------+-------------+
+
+  Datasheet:
+    MCP48x1: https://ww1.microchip.com/downloads/en/DeviceDoc/22244B.pdf
+    MCP48x2: https://ww1.microchip.com/downloads/en/DeviceDoc/20002249B.pdf
+
+maintainers:
+  - Anshul Dalal <anshulusr@gmail.com>
+
+properties:
+  compatible:
+    enum:
+      - microchip,mcp4801
+      - microchip,mcp4802
+      - microchip,mcp4811
+      - microchip,mcp4812
+      - microchip,mcp4821
+      - microchip,mcp4822
+
+  reg:
+    maxItems: 1
+
+  vdd-supply: true
+
+required:
+  - compatible
+  - reg
+  - vdd-supply
+
+additionalProperties: false
+
+examples:
+  - |
+    spi {
+        #address-cells = <1>;
+        #size-cells = <0>;
+
+        dac@0 {
+            compatible = "microchip,mcp4821";
+            reg = <0>;
+            vdd-supply = <&vdd_regulator>;
+        };
+    };
-- 
2.43.0

[PATCH v2 2/2] iio: dac: driver for MCP4821

[Anshul Dalal]

Adds driver for the MCP48xx series of DACs.

Device uses a simplex SPI channel. To set the value of an output channel,
a 16-bit data of following format must be written:

Bit field | Description
15 [MSB]  | Channel selection bit
            0 -> Channel A
            1 -> Channel B
13        | Output Gain Selection bit
            0 -> 2x Gain (Vref = 4.096V)
            1 -> 1x Gain (Vref = 2.048V)
12        | Output Shutdown Control bit
            0 -> Shutdown the selected channel
            1 -> Active mode operation
11-0 [LSB]| DAC Input Data bits
            Value's big endian representation is taken as input for the
            selected DAC channel. For devices with a resolution of less
            than 12-bits, only the x most significant bits are considered
            where x is the resolution of the device.
Reference: Page#22 [MCP48x2 Datasheet]

Supported devices:
  +---------+--------------+-------------+
  | Device  |  Resolution  |   Channels  |
  |---------|--------------|-------------|
  | MCP4801 |     8-bit    |      1      |
  | MCP4802 |     8-bit    |      2      |
  | MCP4811 |    10-bit    |      1      |
  | MCP4812 |    10-bit    |      2      |
  | MCP4821 |    12-bit    |      1      |
  | MCP4822 |    12-bit    |      2      |
  +---------+--------------+-------------+

Devices tested:
  MCP4821 [12-bit single channel]
  MCP4802 [8-bit dual channel]

Tested on Raspberry Pi Zero 2W

Datasheet: https://ww1.microchip.com/downloads/en/DeviceDoc/22244B.pdf #MCP48x1
Datasheet: https://ww1.microchip.com/downloads/en/DeviceDoc/20002249B.pdf #MCP48x2
Signed-off-by: Anshul Dalal <anshulusr@gmail.com>

---

Changes for v2:
- Changed device ordering to numerical
- Fixed ordering of headers
- Added struct mcp4821_chip_info instead of relying on driver_data from
  spi device ids
- Use scoped_guards for all mutex locks
- Changed write_val from __be16 to u16 in mcp4821_write_raw
  Fixes sparse warning: incorrect type in assignment

Previous versions:
v1: https://lore.kernel.org/lkml/20231117073040.685860-2-anshulusr@gmail.com/
---
 MAINTAINERS               |   7 ++
 drivers/iio/dac/Kconfig   |  10 ++
 drivers/iio/dac/Makefile  |   1 +
 drivers/iio/dac/mcp4821.c | 228 ++++++++++++++++++++++++++++++++++++++
 4 files changed, 246 insertions(+)
 create mode 100644 drivers/iio/dac/mcp4821.c

diff --git a/MAINTAINERS b/MAINTAINERS
index 81d5fc0bba68..8d9274c33c6e 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -13029,6 +13029,13 @@ F:	Documentation/ABI/testing/sysfs-bus-iio-potentiometer-mcp4531
 F:	drivers/iio/potentiometer/mcp4018.c
 F:	drivers/iio/potentiometer/mcp4531.c
 
+MCP4821 DAC DRIVER
+M:	Anshul Dalal <anshulusr@gmail.com>
+L:	linux-iio@vger.kernel.org
+S:	Maintained
+F:	Documentation/devicetree/bindings/iio/dac/microchip,mcp4821.yaml
+F:	drivers/iio/dac/mcp4821.c
+
 MCR20A IEEE-802.15.4 RADIO DRIVER
 M:	Stefan Schmidt <stefan@datenfreihafen.org>
 L:	linux-wpan@vger.kernel.org
diff --git a/drivers/iio/dac/Kconfig b/drivers/iio/dac/Kconfig
index 93b8be183de6..34eb40bb9529 100644
--- a/drivers/iio/dac/Kconfig
+++ b/drivers/iio/dac/Kconfig
@@ -400,6 +400,16 @@ config MCP4728
 	  To compile this driver as a module, choose M here: the module
 	  will be called mcp4728.
 
+config MCP4821
+	tristate "MCP4801/02/11/12/21/22 DAC driver"
+	depends on SPI
+	help
+	  Say yes here to build the driver for the Microchip MCP4801
+	  MCP4802, MCP4811, MCP4812, MCP4821 and MCP4822 DAC devices.
+
+	  To compile this driver as a module, choose M here: the module
+	  will be called mcp4821.
+
 config MCP4922
 	tristate "MCP4902, MCP4912, MCP4922 DAC driver"
 	depends on SPI
diff --git a/drivers/iio/dac/Makefile b/drivers/iio/dac/Makefile
index 5b2bac900d5a..55bf89739d14 100644
--- a/drivers/iio/dac/Makefile
+++ b/drivers/iio/dac/Makefile
@@ -42,6 +42,7 @@ obj-$(CONFIG_MAX5522) += max5522.o
 obj-$(CONFIG_MAX5821) += max5821.o
 obj-$(CONFIG_MCP4725) += mcp4725.o
 obj-$(CONFIG_MCP4728) += mcp4728.o
+obj-$(CONFIG_MCP4821) += mcp4821.o
 obj-$(CONFIG_MCP4922) += mcp4922.o
 obj-$(CONFIG_STM32_DAC_CORE) += stm32-dac-core.o
 obj-$(CONFIG_STM32_DAC) += stm32-dac.o
diff --git a/drivers/iio/dac/mcp4821.c b/drivers/iio/dac/mcp4821.c
new file mode 100644
index 000000000000..7384df71f702
--- /dev/null
+++ b/drivers/iio/dac/mcp4821.c
@@ -0,0 +1,228 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Copyright (C) 2023 Anshul Dalal <anshulusr@gmail.com>
+ *
+ * Driver for Microchip MCP4801, MCP4802, MCP4811, MCP4812, MCP4821 and MCP4822
+ *
+ * Based on the work of:
+ *	Michael Welling (MCP4922 Driver)
+ *
+ * Datasheet:
+ *	MCP48x1: https://ww1.microchip.com/downloads/en/DeviceDoc/22244B.pdf
+ *	MCP48x2: https://ww1.microchip.com/downloads/en/DeviceDoc/20002249B.pdf
+ *
+ * TODO:
+ *	- Configurable gain
+ *	- Regulator control
+ */
+
+#include <linux/module.h>
+#include <linux/mutex.h>
+#include <linux/of.h>
+#include <linux/spi/spi.h>
+
+#include <linux/iio/iio.h>
+#include <linux/iio/types.h>
+
+#include <asm/unaligned.h>
+
+#define MCP4821_ACTIVE_MODE BIT(12)
+#define MCP4802_SECOND_CHAN BIT(15)
+
+/* DAC uses an internal Voltage reference of 4.096V at a gain of 2x */
+#define MCP4821_2X_GAIN_VREF_MV 4096
+
+enum mcp4821_supported_drvice_ids {
+	ID_MCP4801,
+	ID_MCP4802,
+	ID_MCP4811,
+	ID_MCP4812,
+	ID_MCP4821,
+	ID_MCP4822,
+};
+
+struct mcp4821_state {
+	struct spi_device *spi;
+	// Protects dac_value
+	struct mutex lock;
+	u16 dac_value[2];
+};
+
+struct mcp4821_chip_info {
+	const char *name;
+	int num_channels;
+	const struct iio_chan_spec channels[2];
+};
+
+#define MCP4821_CHAN(channel_id, resolution)                          \
+	{                                                             \
+		.type = IIO_VOLTAGE, .output = 1, .indexed = 1,       \
+		.channel = (channel_id),                              \
+		.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),         \
+		.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE), \
+		.scan_type = {                                        \
+			.sign = 'u',                                  \
+			.realbits = (resolution),                     \
+			.storagebits = 16,                            \
+			.shift = 12 - (resolution),                   \
+		},                                                    \
+	}
+
+static const struct mcp4821_chip_info mcp4821_chip_info_table[6] = {
+	[ID_MCP4801] = {
+			.name = "mcp4801",
+			.num_channels = 1,
+			.channels = { MCP4821_CHAN(0, 8) }
+			},
+	[ID_MCP4802] = {
+			.name = "mcp4802",
+			.num_channels = 2,
+			.channels = { MCP4821_CHAN(0, 8),
+				       MCP4821_CHAN(1, 8) }
+			},
+	[ID_MCP4811] = {
+			.name = "mcp4811",
+			.num_channels = 1,
+			.channels = { MCP4821_CHAN(0, 10) }
+			},
+	[ID_MCP4812] = {
+			.name = "mcp4812",
+			.num_channels = 2,
+			.channels = { MCP4821_CHAN(0, 10),
+				       MCP4821_CHAN(1, 10) }
+			},
+	[ID_MCP4821] = {
+			.name = "mcp4821",
+			.num_channels = 1,
+			.channels = { MCP4821_CHAN(0, 12) }
+			},
+	[ID_MCP4822] = {
+			.name = "mcp4822",
+			.num_channels = 2,
+			.channels = { MCP4821_CHAN(0, 12),
+				       MCP4821_CHAN(1, 12) }
+			},
+};
+
+static int mcp4821_read_raw(struct iio_dev *indio_dev,
+			    struct iio_chan_spec const *chan, int *val,
+			    int *val2, long mask)
+{
+	struct mcp4821_state *state;
+
+	switch (mask) {
+	case IIO_CHAN_INFO_RAW:
+		state = iio_priv(indio_dev);
+		scoped_guard(mutex, &state->lock)
+			*val = state->dac_value[chan->channel];
+		return IIO_VAL_INT;
+	case IIO_CHAN_INFO_SCALE:
+		*val = MCP4821_2X_GAIN_VREF_MV;
+		*val2 = chan->scan_type.realbits;
+		return IIO_VAL_FRACTIONAL_LOG2;
+	default:
+		return -EINVAL;
+	}
+}
+
+static int mcp4821_write_raw(struct iio_dev *indio_dev,
+			     struct iio_chan_spec const *chan, int val,
+			     int val2, long mask)
+{
+	struct mcp4821_state *state;
+	u16 write_val;
+	__be16 write_buffer;
+	int ret;
+	bool is_value_valid = val >= 0 && val < BIT(chan->scan_type.realbits) &&
+			      val2 == 0;
+
+	if (!is_value_valid)
+		return -EINVAL;
+	if (mask != IIO_CHAN_INFO_RAW)
+		return -EINVAL;
+
+	state = iio_priv(indio_dev);
+	write_val = MCP4821_ACTIVE_MODE | val << chan->scan_type.shift;
+	if (chan->channel)
+		write_val |= MCP4802_SECOND_CHAN;
+	put_unaligned_be16(write_val, &write_buffer);
+	ret = spi_write(state->spi, &write_buffer, sizeof(write_buffer));
+	if (ret) {
+		dev_err(&state->spi->dev, "Failed to write to device: %d", ret);
+		return ret;
+	}
+
+	scoped_guard(mutex, &state->lock)
+		state->dac_value[chan->channel] = val;
+	return 0;
+}
+
+static const struct iio_info mcp4821_info = {
+	.read_raw = &mcp4821_read_raw,
+	.write_raw = &mcp4821_write_raw,
+};
+
+static int mcp4821_probe(struct spi_device *spi)
+{
+	struct iio_dev *indio_dev;
+	struct mcp4821_state *state;
+	const struct mcp4821_chip_info *info;
+
+	indio_dev = devm_iio_device_alloc(&spi->dev, sizeof(*state));
+	if (indio_dev == NULL)
+		return -ENOMEM;
+
+	state = iio_priv(indio_dev);
+	state->spi = spi;
+	mutex_init(&state->lock);
+
+	info = spi_get_device_match_data(spi);
+	indio_dev->name = info->name;
+	indio_dev->info = &mcp4821_info;
+	indio_dev->modes = INDIO_DIRECT_MODE;
+	indio_dev->channels = info->channels;
+	indio_dev->num_channels = info->num_channels;
+	return devm_iio_device_register(&spi->dev, indio_dev);
+}
+
+#define MCP4821_COMPATIBLE(of_compatible, id)        \
+	{                                            \
+		.compatible = of_compatible,         \
+		.data = &mcp4821_chip_info_table[id] \
+	}
+
+static const struct of_device_id mcp4821_of_table[] = {
+	MCP4821_COMPATIBLE("microchip,mcp4801", ID_MCP4801),
+	MCP4821_COMPATIBLE("microchip,mcp4802", ID_MCP4802),
+	MCP4821_COMPATIBLE("microchip,mcp4811", ID_MCP4811),
+	MCP4821_COMPATIBLE("microchip,mcp4812", ID_MCP4812),
+	MCP4821_COMPATIBLE("microchip,mcp4821", ID_MCP4821),
+	MCP4821_COMPATIBLE("microchip,mcp4822", ID_MCP4822),
+	{ /* Sentinel */ }
+};
+MODULE_DEVICE_TABLE(of, mcp4821_of_table);
+
+static const struct spi_device_id mcp4821_id_table[] = {
+	{ "mcp4801", (kernel_ulong_t)&mcp4821_chip_info_table[ID_MCP4801]},
+	{ "mcp4802", (kernel_ulong_t)&mcp4821_chip_info_table[ID_MCP4802]},
+	{ "mcp4811", (kernel_ulong_t)&mcp4821_chip_info_table[ID_MCP4811]},
+	{ "mcp4812", (kernel_ulong_t)&mcp4821_chip_info_table[ID_MCP4812]},
+	{ "mcp4821", (kernel_ulong_t)&mcp4821_chip_info_table[ID_MCP4821]},
+	{ "mcp4822", (kernel_ulong_t)&mcp4821_chip_info_table[ID_MCP4822]},
+	{ /* Sentinel */ }
+};
+MODULE_DEVICE_TABLE(spi, mcp4821_id_table);
+
+static struct spi_driver mcp4821_driver = {
+	.driver = {
+		.name = "mcp4821",
+		.of_match_table = mcp4821_of_table,
+	},
+	.probe = mcp4821_probe,
+	.id_table = mcp4821_id_table,
+};
+module_spi_driver(mcp4821_driver);
+
+MODULE_AUTHOR("Anshul Dalal <anshulusr@gmail.com>");
+MODULE_DESCRIPTION("Microchip MCP4821 DAC Driver");
+MODULE_LICENSE("GPL");
-- 
2.43.0

Re: [PATCH v2 1/2] dt-bindings: iio: dac: add MCP4821

[David Lechner]

On Sun, Dec 17, 2023 at 12:11 PM Anshul Dalal <anshulusr@gmail.com> wrote:
>
> Adds support for MCP48xx series of DACs.
>
> Datasheet: https://ww1.microchip.com/downloads/en/DeviceDoc/22244B.pdf #MCP48x1
> Datasheet: https://ww1.microchip.com/downloads/en/DeviceDoc/20002249B.pdf #MCP48x2
> Reviewed-by: Conor Dooley <conor.dooley@microchip.com>
> Signed-off-by: Anshul Dalal <anshulusr@gmail.com>
>
> ---
>
> Changes for v2:
> - Changed order in device table to numerical
> - Made vdd_supply required
> - Added 'Reviewed-by: Conor Dooley'
>
> Previous versions:
> v1: https://lore.kernel.org/lkml/20231117073040.685860-1-anshulusr@gmail.com/
> ---
>  .../bindings/iio/dac/microchip,mcp4821.yaml   | 64 +++++++++++++++++++
>  1 file changed, 64 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/iio/dac/microchip,mcp4821.yaml
>
> diff --git a/Documentation/devicetree/bindings/iio/dac/microchip,mcp4821.yaml b/Documentation/devicetree/bindings/iio/dac/microchip,mcp4821.yaml
> new file mode 100644
> index 000000000000..97da9f9ef450
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/iio/dac/microchip,mcp4821.yaml
> @@ -0,0 +1,64 @@
> +# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/iio/dac/microchip,mcp4821.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: Microchip MCP4821 and similar DACs
> +
> +description: |
> +  Supports MCP48x1 (single channel) and MCP48x2 (dual channel) series of DACs.
> +  Device supports simplex communication over SPI in Mode 0,1 and Mode 1,1.

It seems like SPI modes usually only have one number in them, i.e.
mode 1 and mode 3 in this case, I'm guessing.

> +
> +  +---------+--------------+-------------+
> +  | Device  |  Resolution  |   Channels  |
> +  |---------|--------------|-------------|
> +  | MCP4801 |     8-bit    |      1      |
> +  | MCP4802 |     8-bit    |      2      |
> +  | MCP4811 |    10-bit    |      1      |
> +  | MCP4812 |    10-bit    |      2      |
> +  | MCP4821 |    12-bit    |      1      |
> +  | MCP4822 |    12-bit    |      2      |
> +  +---------+--------------+-------------+
> +
> +  Datasheet:
> +    MCP48x1: https://ww1.microchip.com/downloads/en/DeviceDoc/22244B.pdf
> +    MCP48x2: https://ww1.microchip.com/downloads/en/DeviceDoc/20002249B.pdf
> +
> +maintainers:
> +  - Anshul Dalal <anshulusr@gmail.com>
> +
> +properties:
> +  compatible:
> +    enum:
> +      - microchip,mcp4801
> +      - microchip,mcp4802
> +      - microchip,mcp4811
> +      - microchip,mcp4812
> +      - microchip,mcp4821
> +      - microchip,mcp4822
> +
> +  reg:
> +    maxItems: 1
> +
> +  vdd-supply: true

What about the SHDN and LDAC pins? It seems like all should have an
ldac-gpios property and MCP48x1 should have a shdn-gpios property for
these.

> +
> +required:
> +  - compatible
> +  - reg
> +  - vdd-supply
> +
> +additionalProperties: false
> +
> +examples:
> +  - |
> +    spi {
> +        #address-cells = <1>;
> +        #size-cells = <0>;
> +
> +        dac@0 {
> +            compatible = "microchip,mcp4821";
> +            reg = <0>;
> +            vdd-supply = <&vdd_regulator>;
> +        };
> +    };
> --
> 2.43.0
>
>

Re: [PATCH v2 1/2] dt-bindings: iio: dac: add MCP4821

[David Lechner]

On Sun, Dec 17, 2023 at 7:25 PM David Lechner <dlechner@baylibre.com> wrote:
>
> On Sun, Dec 17, 2023 at 12:11 PM Anshul Dalal <anshulusr@gmail.com> wrote:
> >
> > Adds support for MCP48xx series of DACs.
> >
> > Datasheet: https://ww1.microchip.com/downloads/en/DeviceDoc/22244B.pdf #MCP48x1
> > Datasheet: https://ww1.microchip.com/downloads/en/DeviceDoc/20002249B.pdf #MCP48x2
> > Reviewed-by: Conor Dooley <conor.dooley@microchip.com>
> > Signed-off-by: Anshul Dalal <anshulusr@gmail.com>
> >
> > ---
> >
> > Changes for v2:
> > - Changed order in device table to numerical
> > - Made vdd_supply required
> > - Added 'Reviewed-by: Conor Dooley'
> >
> > Previous versions:
> > v1: https://lore.kernel.org/lkml/20231117073040.685860-1-anshulusr@gmail.com/
> > ---
> >  .../bindings/iio/dac/microchip,mcp4821.yaml   | 64 +++++++++++++++++++
> >  1 file changed, 64 insertions(+)
> >  create mode 100644 Documentation/devicetree/bindings/iio/dac/microchip,mcp4821.yaml
> >
> > diff --git a/Documentation/devicetree/bindings/iio/dac/microchip,mcp4821.yaml b/Documentation/devicetree/bindings/iio/dac/microchip,mcp4821.yaml
> > new file mode 100644
> > index 000000000000..97da9f9ef450
> > --- /dev/null
> > +++ b/Documentation/devicetree/bindings/iio/dac/microchip,mcp4821.yaml
> > @@ -0,0 +1,64 @@
> > +# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
> > +%YAML 1.2
> > +---
> > +$id: http://devicetree.org/schemas/iio/dac/microchip,mcp4821.yaml#
> > +$schema: http://devicetree.org/meta-schemas/core.yaml#
> > +
> > +title: Microchip MCP4821 and similar DACs
> > +
> > +description: |
> > +  Supports MCP48x1 (single channel) and MCP48x2 (dual channel) series of DACs.
> > +  Device supports simplex communication over SPI in Mode 0,1 and Mode 1,1.
>
> It seems like SPI modes usually only have one number in them, i.e.
> mode 1 and mode 3 in this case, I'm guessing.

Oh, and doesn't this mean that we need to include spi-cpha and
spi-cpol properties since they aren't implicit in the bindings anymore
since [1]?

[1]: https://lore.kernel.org/all/20220722191539.90641-2-krzysztof.kozlowski@linaro.org/

>
> > +
> > +  +---------+--------------+-------------+
> > +  | Device  |  Resolution  |   Channels  |
> > +  |---------|--------------|-------------|
> > +  | MCP4801 |     8-bit    |      1      |
> > +  | MCP4802 |     8-bit    |      2      |
> > +  | MCP4811 |    10-bit    |      1      |
> > +  | MCP4812 |    10-bit    |      2      |
> > +  | MCP4821 |    12-bit    |      1      |
> > +  | MCP4822 |    12-bit    |      2      |
> > +  +---------+--------------+-------------+
> > +
> > +  Datasheet:
> > +    MCP48x1: https://ww1.microchip.com/downloads/en/DeviceDoc/22244B.pdf
> > +    MCP48x2: https://ww1.microchip.com/downloads/en/DeviceDoc/20002249B.pdf
> > +
> > +maintainers:
> > +  - Anshul Dalal <anshulusr@gmail.com>
> > +
> > +properties:
> > +  compatible:
> > +    enum:
> > +      - microchip,mcp4801
> > +      - microchip,mcp4802
> > +      - microchip,mcp4811
> > +      - microchip,mcp4812
> > +      - microchip,mcp4821
> > +      - microchip,mcp4822
> > +
> > +  reg:
> > +    maxItems: 1
> > +
> > +  vdd-supply: true
>
> What about the SHDN and LDAC pins? It seems like all should have an
> ldac-gpios property and MCP48x1 should have a shdn-gpios property for
> these.
>
> > +
> > +required:
> > +  - compatible
> > +  - reg
> > +  - vdd-supply
> > +
> > +additionalProperties: false
> > +
> > +examples:
> > +  - |
> > +    spi {
> > +        #address-cells = <1>;
> > +        #size-cells = <0>;
> > +
> > +        dac@0 {
> > +            compatible = "microchip,mcp4821";
> > +            reg = <0>;
> > +            vdd-supply = <&vdd_regulator>;
> > +        };
> > +    };
> > --
> > 2.43.0
> >
> >

Re: [PATCH v2 2/2] iio: dac: driver for MCP4821

[Jonathan Cameron]

On Sun, 17 Dec 2023 23:38:34 +0530
Anshul Dalal <anshulusr@gmail.com> wrote:

> Adds driver for the MCP48xx series of DACs.
> 
> Device uses a simplex SPI channel. To set the value of an output channel,
> a 16-bit data of following format must be written:
> 
> Bit field | Description
> 15 [MSB]  | Channel selection bit
>             0 -> Channel A
>             1 -> Channel B
> 13        | Output Gain Selection bit
>             0 -> 2x Gain (Vref = 4.096V)
>             1 -> 1x Gain (Vref = 2.048V)
> 12        | Output Shutdown Control bit
>             0 -> Shutdown the selected channel
>             1 -> Active mode operation
> 11-0 [LSB]| DAC Input Data bits
>             Value's big endian representation is taken as input for the
>             selected DAC channel. For devices with a resolution of less
>             than 12-bits, only the x most significant bits are considered
>             where x is the resolution of the device.
> Reference: Page#22 [MCP48x2 Datasheet]
> 
> Supported devices:
>   +---------+--------------+-------------+
>   | Device  |  Resolution  |   Channels  |
>   |---------|--------------|-------------|
>   | MCP4801 |     8-bit    |      1      |
>   | MCP4802 |     8-bit    |      2      |
>   | MCP4811 |    10-bit    |      1      |
>   | MCP4812 |    10-bit    |      2      |
>   | MCP4821 |    12-bit    |      1      |
>   | MCP4822 |    12-bit    |      2      |
>   +---------+--------------+-------------+
> 
> Devices tested:
>   MCP4821 [12-bit single channel]
>   MCP4802 [8-bit dual channel]
> 
> Tested on Raspberry Pi Zero 2W
> 
> Datasheet: https://ww1.microchip.com/downloads/en/DeviceDoc/22244B.pdf #MCP48x1
> Datasheet: https://ww1.microchip.com/downloads/en/DeviceDoc/20002249B.pdf #MCP48x2
> Signed-off-by: Anshul Dalal <anshulusr@gmail.com>
> 
>

Hi Anshul,

Various minor comments inline.

Thanks,

Jonathan

> diff --git a/drivers/iio/dac/mcp4821.c b/drivers/iio/dac/mcp4821.c
> new file mode 100644
> index 000000000000..7384df71f702
> --- /dev/null
> +++ b/drivers/iio/dac/mcp4821.c
> @@ -0,0 +1,228 @@
> +// SPDX-License-Identifier: GPL-2.0-or-later
> +/*
> + * Copyright (C) 2023 Anshul Dalal <anshulusr@gmail.com>
> + *
> + * Driver for Microchip MCP4801, MCP4802, MCP4811, MCP4812, MCP4821 and MCP4822
> + *
> + * Based on the work of:
> + *	Michael Welling (MCP4922 Driver)
> + *
> + * Datasheet:
> + *	MCP48x1: https://ww1.microchip.com/downloads/en/DeviceDoc/22244B.pdf
> + *	MCP48x2: https://ww1.microchip.com/downloads/en/DeviceDoc/20002249B.pdf
> + *
> + * TODO:
> + *	- Configurable gain
> + *	- Regulator control
> + */
> +
> +#include <linux/module.h>
> +#include <linux/mutex.h>
> +#include <linux/of.h>
> +#include <linux/spi/spi.h>
> +
> +#include <linux/iio/iio.h>
> +#include <linux/iio/types.h>
> +
> +#include <asm/unaligned.h>
> +
> +#define MCP4821_ACTIVE_MODE BIT(12)
> +#define MCP4802_SECOND_CHAN BIT(15)
> +
> +/* DAC uses an internal Voltage reference of 4.096V at a gain of 2x */
> +#define MCP4821_2X_GAIN_VREF_MV 4096
> +
> +enum mcp4821_supported_drvice_ids {
> +	ID_MCP4801,
> +	ID_MCP4802,
> +	ID_MCP4811,
> +	ID_MCP4812,
> +	ID_MCP4821,
> +	ID_MCP4822,
> +};
> +
> +struct mcp4821_state {
> +	struct spi_device *spi;
> +	// Protects dac_value
/* Protects dac_value */

However I'm not clear why a u16 array needs protecting?
Whilst in theory the compiler might be annoying and do torn writes
(write it as 2 1 byte values) that's pretty unlikely and
we don't normally bother to protect against that.

> +	struct mutex lock;
> +	u16 dac_value[2];
> +};
> +
> +struct mcp4821_chip_info {
> +	const char *name;
> +	int num_channels;
> +	const struct iio_chan_spec channels[2];
> +};
> +
> +#define MCP4821_CHAN(channel_id, resolution)                          \
> +	{                                                             \
> +		.type = IIO_VOLTAGE, .output = 1, .indexed = 1,       \
> +		.channel = (channel_id),                              \
> +		.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),         \
> +		.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE), \
> +		.scan_type = {                                        \
> +			.sign = 'u',                                  \

Not used so don't bother setting it until you add buffered support.

> +			.realbits = (resolution),                     \
> +			.storagebits = 16,                            \

Not used, so don't bother setting it.

> +			.shift = 12 - (resolution),                   \
> +		},                                                    \
> +	}

> +static int mcp4821_read_raw(struct iio_dev *indio_dev,
> +			    struct iio_chan_spec const *chan, int *val,
> +			    int *val2, long mask)
> +{
> +	struct mcp4821_state *state;
> +
> +	switch (mask) {
> +	case IIO_CHAN_INFO_RAW:
> +		state = iio_priv(indio_dev);
> +		scoped_guard(mutex, &state->lock)
> +			*val = state->dac_value[chan->channel];
> +		return IIO_VAL_INT;
> +	case IIO_CHAN_INFO_SCALE:
> +		*val = MCP4821_2X_GAIN_VREF_MV;
> +		*val2 = chan->scan_type.realbits;
> +		return IIO_VAL_FRACTIONAL_LOG2;
> +	default:
> +		return -EINVAL;
> +	}
> +}
> +
> +static int mcp4821_write_raw(struct iio_dev *indio_dev,
> +			     struct iio_chan_spec const *chan, int val,
> +			     int val2, long mask)
> +{
> +	struct mcp4821_state *state;
> +	u16 write_val;
> +	__be16 write_buffer;
> +	int ret;
> +	bool is_value_valid = val >= 0 && val < BIT(chan->scan_type.realbits) &&
> +			      val2 == 0;
> +
> +	if (!is_value_valid)

Check the opposite and drop the local variable that adds nothing.

	if ((val < 0) || (val >= BIT(chan_type).realbits)) || (val2 != 0))
or split it up into checks on val2 in one check then on val in the other.
 
> +		return -EINVAL;
> +	if (mask != IIO_CHAN_INFO_RAW)
> +		return -EINVAL;
> +
> +	state = iio_priv(indio_dev);
I'd do this at point of local variable declaration above.

struct mcp4821_state *state = iio_priv(indio_dev);

> +	write_val = MCP4821_ACTIVE_MODE | val << chan->scan_type.shift;
> +	if (chan->channel)
> +		write_val |= MCP4802_SECOND_CHAN;
> +	put_unaligned_be16(write_val, &write_buffer);
It's aligned given it's a __be16

> +	ret = spi_write(state->spi, &write_buffer, sizeof(write_buffer));
> +	if (ret) {
> +		dev_err(&state->spi->dev, "Failed to write to device: %d", ret);
> +		return ret;
> +	}
> +
> +	scoped_guard(mutex, &state->lock)
> +		state->dac_value[chan->channel] = val;

> +	return 0;
> +}
> +

Jonathan