mux: adgs1408: new driver for Analog Devices ADGS1408/1409 mux

This patch adds basic support for Analog Device ADGS1408/09 SPI mux
controller.

The device is probed and set to a disabled state. It uses the new mux
controller framework.
Signed-off-by: Mircea Caprioru <mircea.caprioru@analog.com>
Signed-off-by: Peter Rosin <peda@axentia.se>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/mux/Kconfig

@@ -21,6 +21,16 @@ config MUX_ADG792A
 	  To compile the driver as a module, choose M here: the module will
 	  be called mux-adg792a.
 
+config MUX_ADGS1408
+	tristate "Analog Devices ADGS1408/ADGS1409 Multiplexers"
+	depends on SPI
+	help
+	  ADGS1408 8:1 multiplexer and ADGS1409 double 4:1 multiplexer
+	  switches.
+
+	  To compile the driver as a module, choose M here: the module will
+	  be called mux-adgs1408.
+
 config MUX_GPIO
 	tristate "GPIO-controlled Multiplexer"
 	depends on GPIOLIB || COMPILE_TEST

drivers/mux/Makefile

@@ -5,10 +5,12 @@
 
 mux-core-objs			:= core.o
 mux-adg792a-objs		:= adg792a.o
+mux-adgs1408-objs		:= adgs1408.o
 mux-gpio-objs			:= gpio.o
 mux-mmio-objs			:= mmio.o
 
 obj-$(CONFIG_MULTIPLEXER)	+= mux-core.o
 obj-$(CONFIG_MUX_ADG792A)	+= mux-adg792a.o
+obj-$(CONFIG_MUX_ADGS1408)	+= mux-adgs1408.o
 obj-$(CONFIG_MUX_GPIO)		+= mux-gpio.o
 obj-$(CONFIG_MUX_MMIO)		+= mux-mmio.o

drivers/mux/adgs1408.c

+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * ADGS1408/ADGS1409 SPI MUX driver
+ *
+ * Copyright 2018 Analog Devices Inc.
+ */
+
+#include <linux/err.h>
+#include <linux/module.h>
+#include <linux/mux/driver.h>
+#include <linux/of_platform.h>
+#include <linux/property.h>
+#include <linux/spi/spi.h>
+
+#define ADGS1408_SW_DATA       (0x01)
+#define ADGS1408_REG_READ(reg) ((reg) | 0x80)
+#define ADGS1408_DISABLE       (0x00)
+#define ADGS1408_MUX(state)    (((state) << 1) | 1)
+
+enum adgs1408_chip_id {
+	ADGS1408 = 1,
+	ADGS1409,
+};
+
+static int adgs1408_spi_reg_write(struct spi_device *spi,
+				  u8 reg_addr, u8 reg_data)
+{
+	u8 tx_buf[2];
+
+	tx_buf[0] = reg_addr;
+	tx_buf[1] = reg_data;
+
+	return spi_write_then_read(spi, tx_buf, sizeof(tx_buf), NULL, 0);
+}
+
+static int adgs1408_set(struct mux_control *mux, int state)
+{
+	struct spi_device *spi = to_spi_device(mux->chip->dev.parent);
+	u8 reg;
+
+	if (state == MUX_IDLE_DISCONNECT)
+		reg = ADGS1408_DISABLE;
+	else
+		reg = ADGS1408_MUX(state);
+
+	return adgs1408_spi_reg_write(spi, ADGS1408_SW_DATA, reg);
+}
+
+static const struct mux_control_ops adgs1408_ops = {
+	.set = adgs1408_set,
+};
+
+static int adgs1408_probe(struct spi_device *spi)
+{
+	struct device *dev = &spi->dev;
+	enum adgs1408_chip_id chip_id;
+	struct mux_chip *mux_chip;
+	struct mux_control *mux;
+	s32 idle_state;
+	int ret;
+
+	chip_id = (enum adgs1408_chip_id)of_device_get_match_data(dev);
+	if (!chip_id)
+		chip_id = spi_get_device_id(spi)->driver_data;
+
+	mux_chip = devm_mux_chip_alloc(dev, 1, 0);
+	if (IS_ERR(mux_chip))
+		return PTR_ERR(mux_chip);
+
+	mux_chip->ops = &adgs1408_ops;
+
+	ret = adgs1408_spi_reg_write(spi, ADGS1408_SW_DATA, ADGS1408_DISABLE);
+	if (ret < 0)
+		return ret;
+
+	ret = device_property_read_u32(dev, "idle-state", (u32 *)&idle_state);
+	if (ret < 0)
+		idle_state = MUX_IDLE_AS_IS;
+
+	mux = mux_chip->mux;
+
+	if (chip_id == ADGS1408)
+		mux->states = 8;
+	else
+		mux->states = 4;
+
+	switch (idle_state) {
+	case MUX_IDLE_DISCONNECT:
+	case MUX_IDLE_AS_IS:
+	case 0 ... 7:
+		/* adgs1409 supports only 4 states */
+		if (idle_state < mux->states) {
+			mux->idle_state = idle_state;
+			break;
+		}
+		/* fall through */
+	default:
+		dev_err(dev, "invalid idle-state %d\n", idle_state);
+		return -EINVAL;
+	}
+
+	return devm_mux_chip_register(dev, mux_chip);
+}
+
+static const struct spi_device_id adgs1408_spi_id[] = {
+	{ "adgs1408", ADGS1408 },
+	{ "adgs1409", ADGS1409 },
+	{ }
+};
+MODULE_DEVICE_TABLE(spi, adgs1408_spi_id);
+
+static const struct of_device_id adgs1408_of_match[] = {
+	{ .compatible = "adi,adgs1408", .data = (void *)ADGS1408, },
+	{ .compatible = "adi,adgs1409", .data = (void *)ADGS1409, },
+	{ }
+};
+MODULE_DEVICE_TABLE(of, adgs1408_of_match);
+
+static struct spi_driver adgs1408_driver = {
+	.driver = {
+		.name = "adgs1408",
+		.of_match_table = of_match_ptr(adgs1408_of_match),
+	},
+	.probe = adgs1408_probe,
+	.id_table = adgs1408_spi_id,
+};
+module_spi_driver(adgs1408_driver);
+
+MODULE_AUTHOR("Mircea Caprioru <mircea.caprioru@analog.com>");
+MODULE_DESCRIPTION("Analog Devices ADGS1408 MUX driver");
+MODULE_LICENSE("GPL v2");