drivers: dac: add support for ltc1660/ltc1665

LTC1665/LTC1660 is a 8/10-bit Digital-to-Analog Converter
(DAC) with eight individual channels.

Signed-off-by: Marcus Folkesson <marcus.folkesson@gmail.com>

drivers/dac/CMakeLists.txt

@@ -9,6 +9,7 @@ zephyr_library_sources_ifdef(CONFIG_DAC_SAM		dac_sam.c)
 zephyr_library_sources_ifdef(CONFIG_DAC_SAM0		dac_sam0.c)
 zephyr_library_sources_ifdef(CONFIG_DAC_DACX0508	dac_dacx0508.c)
 zephyr_library_sources_ifdef(CONFIG_DAC_DACX3608	dac_dacx3608.c)
+zephyr_library_sources_ifdef(CONFIG_DAC_LTC166X     dac_ltc166x.c)
 zephyr_library_sources_ifdef(CONFIG_DAC_SHELL		dac_shell.c)
 zephyr_library_sources_ifdef(CONFIG_DAC_MCP4725		dac_mcp4725.c)
 zephyr_library_sources_ifdef(CONFIG_DAC_MCP4728		dac_mcp4728.c)

drivers/dac/Kconfig

@@ -42,6 +42,8 @@ source "drivers/dac/Kconfig.dacx0508"
 
 source "drivers/dac/Kconfig.dacx3608"
 
+source "drivers/dac/Kconfig.ltc166x"
+
 source "drivers/dac/Kconfig.mcp4725"
 
 source "drivers/dac/Kconfig.mcp4728"

drivers/dac/Kconfig.ltc166x

@@ -0,0 +1,23 @@
+# DAC configuration options
+
+# Copyright (C) 2023 Marcus Folkesson <marcus.folkesson@gmail.com>
+#
+# SPDX-License-Identifier: Apache-2.0
+
+config DAC_LTC166X
+	bool "Linear Technology LTC166X DAC"
+	default y
+	select SPI
+	depends on DT_HAS_LLTC_LTC1660_ENABLED || DT_HAS_LLTC_LTC1665_ENABLED
+	help
+	  Enable the driver for the Linear Technology LTC166X DAC
+
+if DAC_LTC166X
+
+config DAC_LTC166X_INIT_PRIORITY
+	int "Init priority"
+	default 80
+	help
+	  Linear Technology LTC166X DAC device driver initialization priority.
+
+endif # DAC_LTC166X

drivers/dac/dac_ltc166x.c

@@ -0,0 +1,141 @@
+/*
+ * Driver for Linear Technology LTC1660/LTC1665  DAC
+ *
+ * Copyright (C) 2023 Marcus Folkesson <marcus.folkesson@gmail.com>
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#include <zephyr/kernel.h>
+#include <zephyr/drivers/spi.h>
+#include <zephyr/drivers/dac.h>
+#include <zephyr/logging/log.h>
+
+LOG_MODULE_REGISTER(dac_ltc166x, CONFIG_DAC_LOG_LEVEL);
+
+#define LTC166X_REG_MASK               GENMASK(15, 12)
+#define LTC166X_DATA8_MASK             GENMASK(11, 4)
+#define LTC166X_DATA10_MASK            GENMASK(12, 2)
+
+struct ltc166x_config {
+	struct spi_dt_spec bus;
+	uint8_t resolution;
+	uint8_t nchannels;
+};
+
+static int ltc166x_reg_write(const struct device *dev, uint8_t addr,
+			uint32_t data)
+{
+	const struct ltc166x_config *config = dev->config;
+	uint16_t regval;
+
+	regval = FIELD_PREP(LTC166X_REG_MASK, addr);
+
+	if (config->resolution == 10) {
+		regval |= FIELD_PREP(LTC166X_DATA10_MASK, data);
+	} else {
+		regval |= FIELD_PREP(LTC166X_DATA8_MASK, data);
+	}
+
+	const struct spi_buf buf = {
+			.buf = &regval,
+			.len = sizeof(regval),
+	};
+
+	struct spi_buf_set tx = {
+		.buffers = &buf,
+		.count = 1,
+	};
+
+	return spi_write_dt(&config->bus, &tx);
+}
+
+
+static int ltc166x_channel_setup(const struct device *dev,
+				   const struct dac_channel_cfg *channel_cfg)
+{
+	const struct ltc166x_config *config = dev->config;
+
+	if (channel_cfg->channel_id > config->nchannels - 1) {
+		LOG_ERR("Unsupported channel %d", channel_cfg->channel_id);
+		return -ENOTSUP;
+	}
+
+	if (channel_cfg->resolution != config->resolution) {
+		LOG_ERR("Unsupported resolution %d", channel_cfg->resolution);
+		return -ENOTSUP;
+	}
+
+	return 0;
+}
+
+static int ltc166x_write_value(const struct device *dev, uint8_t channel,
+				uint32_t value)
+{
+	const struct ltc166x_config *config = dev->config;
+
+	if (channel > config->nchannels - 1) {
+		LOG_ERR("unsupported channel %d", channel);
+		return -ENOTSUP;
+	}
+
+	if (value >= (1 << config->resolution)) {
+		LOG_ERR("Value %d out of range", value);
+		return -EINVAL;
+	}
+
+	return ltc166x_reg_write(dev, channel + 1, value);
+}
+
+static int ltc166x_init(const struct device *dev)
+{
+	const struct ltc166x_config *config = dev->config;
+
+	if (!spi_is_ready_dt(&config->bus)) {
+		LOG_ERR("SPI bus %s not ready", config->bus.bus->name);
+		return -ENODEV;
+	}
+	return 0;
+}
+
+static const struct dac_driver_api ltc166x_driver_api = {
+	.channel_setup = ltc166x_channel_setup,
+	.write_value = ltc166x_write_value,
+};
+
+
+#define INST_DT_LTC166X(inst, t) DT_INST(inst, lltc_ltc##t)
+
+#define LTC166X_DEVICE(t, n, res, nchan) \
+	static const struct ltc166x_config ltc##t##_config_##n = { \
+		.bus = SPI_DT_SPEC_GET(INST_DT_LTC166X(n, t), \
+			SPI_OP_MODE_MASTER | \
+			SPI_WORD_SET(8), 0), \
+		.resolution = res, \
+		.nchannels = nchan, \
+	}; \
+	DEVICE_DT_DEFINE(INST_DT_LTC166X(n, t), \
+			    &ltc166x_init, NULL, \
+			    NULL, \
+			    &ltc##t##_config_##n, POST_KERNEL, \
+			    CONFIG_DAC_LTC166X_INIT_PRIORITY, \
+			    &ltc166x_driver_api)
+
+/*
+ * LTC1660: 10-bit
+ */
+#define LTC1660_DEVICE(n) LTC166X_DEVICE(1660, n, 10, 8)
+
+/*
+ * LTC1665: 8-bit
+ */
+#define LTC1665_DEVICE(n) LTC166X_DEVICE(1665, n, 8, 8)
+
+#define CALL_WITH_ARG(arg, expr) expr(arg)
+
+#define INST_DT_LTC166X_FOREACH(t, inst_expr) \
+	LISTIFY(DT_NUM_INST_STATUS_OKAY(lltc_ltc##t), \
+		     CALL_WITH_ARG, (), inst_expr)
+
+INST_DT_LTC166X_FOREACH(1660, LTC1660_DEVICE);
+INST_DT_LTC166X_FOREACH(1665, LTC1665_DEVICE);