gpio: add driver for MAX7300 I2C GPIO extender

Add the MAX7300-I2C variant of the MAX7301-SPI version.  Both chips share
the same core logic, so the generic part of the in-kernel SPI-driver is
refactored into a generic part.  The I2C and SPI specific funtions are
then wrapped into seperate drivers picking up the generic part.

Signed-off-by: Wolfram Sang <w.sang@pengutronix.de>
Cc: Juergen Beisert <j.beisert@pengutronix.de>
Cc: David Brownell <dbrownell@users.sourceforge.net>
Cc: Jean Delvare <khali@linux-fr.org>
Cc: Anton Vorontsov <avorontsov@ru.mvista.com>
Cc: Randy Dunlap <randy.dunlap@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 244 insertions, 0 deletions

diff --git a/drivers/gpio/max730x.c b/drivers/gpio/max730x.c
new file mode 100644
index 000000000000..c9bced55f82b
--- /dev/null
+++ b/drivers/gpio/max730x.c
@@ -0,0 +1,244 @@
+/**
+ * drivers/gpio/max7301.c
+ *
+ * Copyright (C) 2006 Juergen Beisert, Pengutronix
+ * Copyright (C) 2008 Guennadi Liakhovetski, Pengutronix
+ * Copyright (C) 2009 Wolfram Sang, Pengutronix
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ * The Maxim MAX7300/1 device is an I2C/SPI driven GPIO expander. There are
+ * 28 GPIOs. 8 of them can trigger an interrupt. See datasheet for more
+ * details
+ * Note:
+ * - DIN must be stable at the rising edge of clock.
+ * - when writing:
+ *   - always clock in 16 clocks at once
+ *   - at DIN: D15 first, D0 last
+ *   - D0..D7 = databyte, D8..D14 = commandbyte
+ *   - D15 = low -> write command
+ * - when reading
+ *   - always clock in 16 clocks at once
+ *   - at DIN: D15 first, D0 last
+ *   - D0..D7 = dummy, D8..D14 = register address
+ *   - D15 = high -> read command
+ *   - raise CS and assert it again
+ *   - always clock in 16 clocks at once
+ *   - at DOUT: D15 first, D0 last
+ *   - D0..D7 contains the data from the first cycle
+ *
+ * The driver exports a standard gpiochip interface
+ */
+
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/platform_device.h>
+#include <linux/mutex.h>
+#include <linux/spi/max7301.h>
+#include <linux/gpio.h>
+
+/*
+ * Pin configurations, see MAX7301 datasheet page 6
+ */
+#define PIN_CONFIG_MASK 0x03
+#define PIN_CONFIG_IN_PULLUP 0x03
+#define PIN_CONFIG_IN_WO_PULLUP 0x02
+#define PIN_CONFIG_OUT 0x01
+
+#define PIN_NUMBER 28
+
+static int max7301_direction_input(struct gpio_chip *chip, unsigned offset)
+{
+        struct max7301 *ts = container_of(chip, struct max7301, chip);
+        u8 *config;
+        u8 offset_bits;
+        int ret;
+
+        /* First 4 pins are unused in the controller */
+        offset += 4;
+        offset_bits = (offset & 3) << 1;
+
+        config = &ts->port_config[offset >> 2];
+
+        mutex_lock(&ts->lock);
+
+        /* Standard GPIO API doesn't support pull-ups, has to be extended.
+         * Hard-coding no pollup for now. */
+        *config = (*config & ~(PIN_CONFIG_MASK << offset_bits))
+                           | (PIN_CONFIG_IN_WO_PULLUP << offset_bits);
+
+        ret = ts->write(ts->dev, 0x08 + (offset >> 2), *config);
+
+        mutex_unlock(&ts->lock);
+
+        return ret;
+}
+
+static int __max7301_set(struct max7301 *ts, unsigned offset, int value)
+{
+        if (value) {
+                ts->out_level |= 1 << offset;
+                return ts->write(ts->dev, 0x20 + offset, 0x01);
+        } else {
+                ts->out_level &= ~(1 << offset);
+                return ts->write(ts->dev, 0x20 + offset, 0x00);
+        }
+}
+
+static int max7301_direction_output(struct gpio_chip *chip, unsigned offset,
+                                    int value)
+{
+        struct max7301 *ts = container_of(chip, struct max7301, chip);
+        u8 *config;
+        u8 offset_bits;
+        int ret;
+
+        /* First 4 pins are unused in the controller */
+        offset += 4;
+        offset_bits = (offset & 3) << 1;
+
+        config = &ts->port_config[offset >> 2];
+
+        mutex_lock(&ts->lock);
+
+        *config = (*config & ~(PIN_CONFIG_MASK << offset_bits))
+                           | (PIN_CONFIG_OUT << offset_bits);
+
+        ret = __max7301_set(ts, offset, value);
+
+        if (!ret)
+                ret = ts->write(ts->dev, 0x08 + (offset >> 2), *config);
+
+        mutex_unlock(&ts->lock);
+
+        return ret;
+}
+
+static int max7301_get(struct gpio_chip *chip, unsigned offset)
+{
+        struct max7301 *ts = container_of(chip, struct max7301, chip);
+        int config, level = -EINVAL;
+
+        /* First 4 pins are unused in the controller */
+        offset += 4;
+
+        mutex_lock(&ts->lock);
+
+        config = (ts->port_config[offset >> 2] >> ((offset & 3) << 1))
+                        & PIN_CONFIG_MASK;
+
+        switch (config) {
+        case PIN_CONFIG_OUT:
+                /* Output: return cached level */
+                level =  !!(ts->out_level & (1 << offset));
+                break;
+        case PIN_CONFIG_IN_WO_PULLUP:
+        case PIN_CONFIG_IN_PULLUP:
+                /* Input: read out */
+                level = ts->read(ts->dev, 0x20 + offset) & 0x01;
+        }
+        mutex_unlock(&ts->lock);
+
+        return level;
+}
+
+static void max7301_set(struct gpio_chip *chip, unsigned offset, int value)
+{
+        struct max7301 *ts = container_of(chip, struct max7301, chip);
+
+        /* First 4 pins are unused in the controller */
+        offset += 4;
+
+        mutex_lock(&ts->lock);
+
+        __max7301_set(ts, offset, value);
+
+        mutex_unlock(&ts->lock);
+}
+
+int __devinit __max730x_probe(struct max7301 *ts)
+{
+        struct device *dev = ts->dev;
+        struct max7301_platform_data *pdata;
+        int i, ret;
+
+        pdata = dev->platform_data;
+        if (!pdata || !pdata->base) {
+                dev_err(dev, "incorrect or missing platform data\n");
+                return -EINVAL;
+        }
+
+        mutex_init(&ts->lock);
+        dev_set_drvdata(dev, ts);
+
+        /* Power up the chip and disable IRQ output */
+        ts->write(dev, 0x04, 0x01);
+
+        ts->chip.label = dev->driver->name;
+
+        ts->chip.direction_input = max7301_direction_input;
+        ts->chip.get = max7301_get;
+        ts->chip.direction_output = max7301_direction_output;
+        ts->chip.set = max7301_set;
+
+        ts->chip.base = pdata->base;
+        ts->chip.ngpio = PIN_NUMBER;
+        ts->chip.can_sleep = 1;
+        ts->chip.dev = dev;
+        ts->chip.owner = THIS_MODULE;
+
+        /*
+         * tristate all pins in hardware and cache the
+         * register values for later use.
+         */
+        for (i = 1; i < 8; i++) {
+                int j;
+                /* 0xAA means input with internal pullup disabled */
+                ts->write(dev, 0x08 + i, 0xAA);
+                ts->port_config[i] = 0xAA;
+                for (j = 0; j < 4; j++) {
+                        int offset = (i - 1) * 4 + j;
+                        ret = max7301_direction_input(&ts->chip, offset);
+                        if (ret)
+                                goto exit_destroy;
+                }
+        }
+
+        ret = gpiochip_add(&ts->chip);
+        if (ret)
+                goto exit_destroy;
+
+        return ret;
+
+exit_destroy:
+        dev_set_drvdata(dev, NULL);
+        mutex_destroy(&ts->lock);
+        return ret;
+}
+EXPORT_SYMBOL_GPL(__max730x_probe);
+
+int __devexit __max730x_remove(struct device *dev)
+{
+        struct max7301 *ts = dev_get_drvdata(dev);
+        int ret;
+
+        if (ts == NULL)
+                return -ENODEV;
+
+        dev_set_drvdata(dev, NULL);
+
+        /* Power down the chip and disable IRQ output */
+        ts->write(dev, 0x04, 0x00);
+
+        ret = gpiochip_remove(&ts->chip);
+        if (!ret) {
+                mutex_destroy(&ts->lock);
+                kfree(ts);
+        } else
+                dev_err(dev, "Failed to remove GPIO controller: %d\n", ret);
+
+        return ret;
+}
+EXPORT_SYMBOL_GPL(__max730x_remove);