iio: stx104: Add GPIO support for the Apex Embedded Systems STX104

The Apex Embedded Systems STX104 device features eight lines of digital
I/O (four digital inputs and four digital outputs). This patch adds GPIO
support for these eight lines of digital I/O via GPIOLIB.

Cc: Alexandre Courbot <gnurou@gmail.com>
Signed-off-by: William Breathitt Gray <vilhelm.gray@gmail.com>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

2 files changed, 129 insertions, 7 deletions

diff --git a/drivers/iio/dac/Kconfig b/drivers/iio/dac/Kconfig
index 61d5008bff5c..b3feb0bf3aa3 100644
--- a/drivers/iio/dac/Kconfig
+++ b/drivers/iio/dac/Kconfig
@@ -246,13 +246,14 @@ config MCP4922
           will be called mcp4922.
 
 config STX104
-        tristate "Apex Embedded Systems STX104 DAC driver"
+        tristate "Apex Embedded Systems STX104 driver"
         depends on ISA
+        select GPIOLIB
         help
-          Say yes here to build support for the 2-channel DAC on the Apex
-          Embedded Systems STX104 integrated analog PC/104 card. The base port
-          addresses for the devices may be configured via the "base" module
-          parameter array.
+          Say yes here to build support for the 2-channel DAC and GPIO on the
+          Apex Embedded Systems STX104 integrated analog PC/104 card. The base
+          port addresses for the devices may be configured via the base array
+          module parameter.
 
 config VF610_DAC
         tristate "Vybrid vf610 DAC driver"
diff --git a/drivers/iio/dac/stx104.c b/drivers/iio/dac/stx104.c
index 174f4b75ceed..e0f31a12c87f 100644
--- a/drivers/iio/dac/stx104.c
+++ b/drivers/iio/dac/stx104.c
@@ -14,6 +14,7 @@
 #include <linux/bitops.h>
 #include <linux/device.h>
 #include <linux/errno.h>
+#include <linux/gpio/driver.h>
 #include <linux/iio/iio.h>
 #include <linux/iio/types.h>
 #include <linux/io.h>
@@ -21,6 +22,7 @@
 #include <linux/isa.h>
 #include <linux/module.h>
 #include <linux/moduleparam.h>
+#include <linux/spinlock.h>
 
 #define STX104_NUM_CHAN 2
 
@@ -56,6 +58,20 @@ struct stx104_iio {
         unsigned base;
 };
 
+/**
+ * struct stx104_gpio - GPIO device private data structure
+ * @chip:       instance of the gpio_chip
+ * @lock:       synchronization lock to prevent I/O race conditions
+ * @base:       base port address of the GPIO device
+ * @out_state:  output bits state
+ */
+struct stx104_gpio {
+        struct gpio_chip chip;
+        spinlock_t lock;
+        unsigned int base;
+        unsigned int out_state;
+};
+
 static int stx104_read_raw(struct iio_dev *indio_dev,
         struct iio_chan_spec const *chan, int *val, int *val2, long mask)
 {
@@ -95,15 +111,81 @@ static const struct iio_chan_spec stx104_channels[STX104_NUM_CHAN] = {
         STX104_CHAN(1)
 };
 
+static int stx104_gpio_get_direction(struct gpio_chip *chip,
+        unsigned int offset)
+{
+        if (offset < 4)
+                return 1;
+
+        return 0;
+}
+
+static int stx104_gpio_direction_input(struct gpio_chip *chip,
+        unsigned int offset)
+{
+        if (offset >= 4)
+                return -EINVAL;
+
+        return 0;
+}
+
+static int stx104_gpio_direction_output(struct gpio_chip *chip,
+        unsigned int offset, int value)
+{
+        if (offset < 4)
+                return -EINVAL;
+
+        chip->set(chip, offset, value);
+        return 0;
+}
+
+static int stx104_gpio_get(struct gpio_chip *chip, unsigned int offset)
+{
+        struct stx104_gpio *const stx104gpio = gpiochip_get_data(chip);
+
+        if (offset >= 4)
+                return -EINVAL;
+
+        return !!(inb(stx104gpio->base) & BIT(offset));
+}
+
+static void stx104_gpio_set(struct gpio_chip *chip, unsigned int offset,
+        int value)
+{
+        struct stx104_gpio *const stx104gpio = gpiochip_get_data(chip);
+        const unsigned int mask = BIT(offset) >> 4;
+        unsigned long flags;
+
+        if (offset < 4)
+                return;
+
+        spin_lock_irqsave(&stx104gpio->lock, flags);
+
+        if (value)
+                stx104gpio->out_state |= mask;
+        else
+                stx104gpio->out_state &= ~mask;
+
+        outb(stx104gpio->out_state, stx104gpio->base);
+
+        spin_unlock_irqrestore(&stx104gpio->lock, flags);
+}
+
 static int stx104_probe(struct device *dev, unsigned int id)
 {
         struct iio_dev *indio_dev;
         struct stx104_iio *priv;
+        struct stx104_gpio *stx104gpio;
+        int err;
 
         indio_dev = devm_iio_device_alloc(dev, sizeof(*priv));
         if (!indio_dev)
                 return -ENOMEM;
 
+        stx104gpio = devm_kzalloc(dev, sizeof(*stx104gpio), GFP_KERNEL);
+        if (!stx104gpio)
+                return -ENOMEM;
+
         if (!devm_request_region(dev, base[id], STX104_EXTENT,
                 dev_name(dev))) {
                 dev_err(dev, "Unable to lock port addresses (0x%X-0x%X)\n",
@@ -124,14 +206,53 @@ static int stx104_probe(struct device *dev, unsigned int id)
         outw(0, base[id] + 4);
         outw(0, base[id] + 6);
 
-        return devm_iio_device_register(dev, indio_dev);
+        err = devm_iio_device_register(dev, indio_dev);
+        if (err) {
+                dev_err(dev, "IIO device registering failed (%d)\n", err);
+                return err;
+        }
+
+        stx104gpio->chip.label = dev_name(dev);
+        stx104gpio->chip.parent = dev;
+        stx104gpio->chip.owner = THIS_MODULE;
+        stx104gpio->chip.base = -1;
+        stx104gpio->chip.ngpio = 8;
+        stx104gpio->chip.get_direction = stx104_gpio_get_direction;
+        stx104gpio->chip.direction_input = stx104_gpio_direction_input;
+        stx104gpio->chip.direction_output = stx104_gpio_direction_output;
+        stx104gpio->chip.get = stx104_gpio_get;
+        stx104gpio->chip.set = stx104_gpio_set;
+        stx104gpio->base = base[id] + 3;
+        stx104gpio->out_state = 0x0;
+
+        spin_lock_init(&stx104gpio->lock);
+
+        dev_set_drvdata(dev, stx104gpio);
+
+        err = gpiochip_add_data(&stx104gpio->chip, stx104gpio);
+        if (err) {
+                dev_err(dev, "GPIO registering failed (%d)\n", err);
+                return err;
+        }
+
+        return 0;
+}
+
+static int stx104_remove(struct device *dev, unsigned int id)
+{
+        struct stx104_gpio *const stx104gpio = dev_get_drvdata(dev);
+
+        gpiochip_remove(&stx104gpio->chip);
+
+        return 0;
 }
 
 static struct isa_driver stx104_driver = {
         .probe = stx104_probe,
         .driver = {
                 .name = "stx104"
-        }
+        },
+        .remove = stx104_remove
 };
 
 static void __exit stx104_exit(void)