@@ -1622,6 +1622,14 @@ config GPIO_MAX7301
help
GPIO driver for Maxim MAX7301 SPI-based GPIO expander.
+config GPIO_MAX7317
+ tristate "Maxim MAX7317 GPIO expander"
+ depends on SPI
+ help
+ GPIO driver for Maxim MAX7317 SPI-based GPIO expander.
+ The MAX7317 is a serial-interfaced gpio extender, with
+ 10 ports.
+
config GPIO_MC33880
tristate "Freescale MC33880 high-side/low-side switch"
help
@@ -89,6 +89,7 @@ obj-$(CONFIG_GPIO_MAX7300) += gpio-max7300.o
obj-$(CONFIG_GPIO_MAX7301) += gpio-max7301.o
obj-$(CONFIG_GPIO_MAX730X) += gpio-max730x.o
obj-$(CONFIG_GPIO_MAX732X) += gpio-max732x.o
+obj-$(CONFIG_GPIO_MAX7317) += gpio-max7317.o
obj-$(CONFIG_GPIO_MAX77620) += gpio-max77620.o
obj-$(CONFIG_GPIO_MAX77650) += gpio-max77650.o
obj-$(CONFIG_GPIO_MB86S7X) += gpio-mb86s7x.o
new file mode 100644
@@ -0,0 +1,221 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2021, Lukasz Zemla, Woodward Inc.
+ *
+ */
+
+#include <linux/gpio.h>
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/mutex.h>
+#include <linux/platform_device.h>
+#include <linux/slab.h>
+#include <linux/spi/spi.h>
+#include <linux/platform_data/max7317.h>
+
+/* MAX7317 has 10 pins, controlled by 10 internal registers,
+ * addressed as 0x00 - 0x09.
+ */
+#define PIN_NUMBER 10
+
+/* Register code to read inputs from 7 to 0 */
+#define REG_CODE_READ_PORTS_7_TO_0 ((u8)0x0E)
+/* Register code to read inputs from 9 to 8 */
+#define REG_CODE_READ_PORTS_9_TO_8 ((u8)0x0F)
+
+struct max7317 {
+ struct mutex lock;
+ struct gpio_chip chip;
+ struct device *dev;
+};
+
+struct max7317_platform_data {
+ /* number assigned to the first GPIO */
+ unsigned int gpio_base;
+};
+
+/* A write to the MAX7317 means one message with one transfer */
+static int max7317_spi_write(struct device *dev, unsigned int reg,
+ unsigned int val)
+{
+ struct spi_device *spi = to_spi_device(dev);
+ u16 word = ((reg & 0x7F) << 8) | (val & 0xFF);
+
+ return spi_write_then_read(spi, &word, sizeof(word), NULL, 0);
+}
+
+/* A read from the MAX7317 means two transfers, with chip select going high between them. */
+static int max7317_spi_read(struct device *dev, unsigned int reg)
+{
+ int ret;
+ u16 word;
+ struct spi_device *spi = to_spi_device(dev);
+
+ word = 0x8000 | (reg << 8);
+
+ /* First transfer: ask to read register */
+ ret = spi_write(spi, &word, sizeof(word));
+ if (ret)
+ return ret;
+
+ /* Second transfer: read register value */
+ ret = spi_read(spi, &word, sizeof(word));
+ if (ret)
+ return ret;
+
+ return word & 0xff;
+}
+
+static void max7317_set(struct gpio_chip *chip, unsigned int offset, int value)
+{
+ struct max7317 *ts = gpiochip_get_data(chip);
+
+ mutex_lock(&ts->lock);
+ max7317_spi_write(ts->dev, offset, value);
+ mutex_unlock(&ts->lock);
+}
+
+static int max7317_get(struct gpio_chip *chip, unsigned int offset)
+{
+ struct max7317 *ts = gpiochip_get_data(chip);
+ unsigned int reg, val, mask, shift;
+ int inputs;
+
+ if (offset < 8) {
+ reg = REG_CODE_READ_PORTS_7_TO_0;
+ mask = 1u << offset;
+ shift = offset;
+ } else {
+ reg = REG_CODE_READ_PORTS_9_TO_8;
+ mask = 1u << (offset - 8);
+ shift = offset - 8;
+ }
+
+ mutex_lock(&ts->lock);
+ inputs = max7317_spi_read(ts->dev, reg);
+ mutex_unlock(&ts->lock);
+
+ val = ((unsigned int)inputs & mask) >> shift;
+
+ return (int)val;
+}
+
+static int max7317_direction_input(struct gpio_chip *chip, unsigned int offset)
+{
+ /* Per documentation:
+ * 'Configure a port as an input by setting its output register to 0x01,
+ * which sets the port output high impedance (Table 4).
+ */
+ max7317_set(chip, offset, 1);
+ return 0;
+}
+
+static int max7301_direction_output(struct gpio_chip *chip, unsigned int offset,
+ int value)
+{
+ max7317_set(chip, offset, value);
+ return 0;
+}
+
+static int max7317_probe(struct spi_device *spi)
+{
+ struct max7317 *ts;
+ struct device *dev;
+ struct max7317_platform_data *pdata;
+ int ret;
+
+ /* bits_per_word cannot be configured in platform data */
+ spi->bits_per_word = 16;
+ ret = spi_setup(spi);
+ if (ret < 0)
+ return ret;
+
+ ts = devm_kzalloc(&spi->dev, sizeof(struct max7317), GFP_KERNEL);
+ if (!ts)
+ return -ENOMEM;
+
+ ts->dev = &spi->dev;
+
+ dev = ts->dev;
+
+ pdata = dev_get_platdata(dev);
+
+ mutex_init(&ts->lock);
+ dev_set_drvdata(dev, ts);
+
+ if (pdata)
+ ts->chip.base = pdata->gpio_base;
+ else
+ ts->chip.base = -1;
+
+ ts->chip.label = dev->driver->name;
+
+ ts->chip.direction_input = max7317_direction_input;
+ ts->chip.get = max7317_get;
+ ts->chip.direction_output = max7301_direction_output;
+ ts->chip.set = max7317_set;
+
+ ts->chip.ngpio = PIN_NUMBER;
+ ts->chip.can_sleep = true;
+ ts->chip.parent = dev;
+ ts->chip.owner = THIS_MODULE;
+
+ ret = gpiochip_add_data(&ts->chip, ts);
+ if (!ret)
+ return ret;
+
+ mutex_destroy(&ts->lock);
+ return ret;
+}
+
+static void max7317_remove(struct spi_device *spi)
+{
+ struct max7317 *ts = dev_get_drvdata(&spi->dev);
+
+ if (!ts)
+ return;
+
+ gpiochip_remove(&ts->chip);
+ mutex_destroy(&ts->lock);
+}
+
+static const struct spi_device_id max7317_id[] = {
+ { "max7317", 0 },
+ { }
+};
+MODULE_DEVICE_TABLE(spi, max7317_id);
+
+static const struct of_device_id max7317_of_table[] = {
+ { .compatible = "maxim,max7317" },
+ { }
+};
+MODULE_DEVICE_TABLE(of, max7317_of_table);
+
+static struct spi_driver max7317_driver = {
+ .driver = {
+ .name = "max7317",
+ .of_match_table = of_match_ptr(max7317_of_table),
+ },
+ .probe = max7317_probe,
+ .remove = max7317_remove,
+ .id_table = max7317_id,
+};
+
+static int __init max7317_init(void)
+{
+ return spi_register_driver(&max7317_driver);
+}
+/* register after spi postcore initcall and before
+ * subsys initcalls that may rely on these GPIOs
+ */
+subsys_initcall(max7317_init);
+
+static void __exit max7317_exit(void)
+{
+ spi_unregister_driver(&max7317_driver);
+}
+module_exit(max7317_exit);
+
+MODULE_AUTHOR("Lukasz Zemla");
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("MAX7317 GPIO-Expander");