gpio: max730x: make pullups configurable via platformdata

The gpios on the max730x chips have support for internal pullups while in
input mode.

This patch adds support for configuring these pullups via platform data.
A new member ("input_pullup_active") to the platform data struct is
introduced.  A set bit in this variable activates the pullups while the
respective port is in input mode.  This is a compatible enhancement since
unset bits lead to disables pullups which was the default in the original
driver.

_Note_: the 4 lowest bits in "input_pullup_active" are unused because the
first 4 ports of the controller are not used, too.

Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
Reviewed-by: Wolfram Sang <w.sang@pengutronix.de>
Cc: David Brownell <david-b@pacbell.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

drivers/gpio/max730x.c

@@ -54,7 +54,7 @@ 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;
+	u8 offset_bits, pin_config;
 	int ret;
 
 	/* First 4 pins are unused in the controller */
@@ -63,12 +63,15 @@ static int max7301_direction_input(struct gpio_chip *chip, unsigned offset)
 
 	config = &ts->port_config[offset >> 2];
 
+	if (ts->input_pullup_active & BIT(offset))
+		pin_config = PIN_CONFIG_IN_PULLUP;
+	else
+		pin_config = PIN_CONFIG_IN_WO_PULLUP;
+
 	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);
+			   | (pin_config << offset_bits);
 
 	ret = ts->write(ts->dev, 0x08 + (offset >> 2), *config);
 
@@ -177,6 +180,7 @@ int __devinit __max730x_probe(struct max7301 *ts)
 	/* Power up the chip and disable IRQ output */
 	ts->write(dev, 0x04, 0x01);
 
+	ts->input_pullup_active = pdata->input_pullup_active;
 	ts->chip.label = dev->driver->name;
 
 	ts->chip.direction_input = max7301_direction_input;
@@ -191,13 +195,17 @@ int __devinit __max730x_probe(struct max7301 *ts)
 	ts->chip.owner = THIS_MODULE;
 
 	/*
-	 * tristate all pins in hardware and cache the
+	 * initialize pullups according to platform data 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);
+		/*
+		 * initialize port_config with "0xAA", which means
+		 * input with internal pullup disabled. This is needed
+		 * to avoid writing zeros (in the inner for loop),
+		 * which is not allowed according to the datasheet.
+		 */
 		ts->port_config[i] = 0xAA;
 		for (j = 0; j < 4; j++) {
 			int offset = (i - 1) * 4 + j;

include/linux/spi/max7301.h

@@ -11,6 +11,7 @@ struct max7301 {
 	struct mutex	lock;
 	u8		port_config[8];	/* field 0 is unused */
 	u32		out_level;	/* cached output levels */
+	u32		input_pullup_active;
 	struct gpio_chip chip;
 	struct device *dev;
 	int (*write)(struct device *dev, unsigned int reg, unsigned int val);
@@ -20,6 +21,13 @@ struct max7301 {
 struct max7301_platform_data {
 	/* number assigned to the first GPIO */
 	unsigned	base;
+	/*
+	 * bitmask controlling the pullup configuration,
+	 *
+	 * _note_ the 4 lowest bits are unused, because the first 4
+	 * ports of the controller are not used, too.
+	 */
+	u32		input_pullup_active;
 };
 
 extern int __max730x_remove(struct device *dev);