Commit 0c36ec31 authored by Juergen Beisert's avatar Juergen Beisert Committed by Linus Torvalds
Browse files

gpio: gpio driver for max7301 SPI GPIO expander 



Maxim's MAX7301 is an SPI GPIO expander with 28 GPIOs.  Note: MAX7301's
interrupt feature is not supported yet.

[akpm@linux-foundation.org: coding-style fixes]
[g.liakhovetski@pengutronix.de: Fix inaccuracies in comments, check spi_setup()
return code, mask off high byte in max7301_read()]
Signed-off-by: default avatarJuergen Beisert <j.beisert@pengutronix.de>
Signed-off-by: default avatarGuennadi Liakhovetski <g.liakhovetski@pengutronix.de>
Cc: Russell King <rmk@arm.linux.org.uk>
Signed-off-by: default avatarDavid Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 65191087

drivers/gpio/Kconfig

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@@ -69,6 +69,12 @@ config GPIO_PCF857X 


comment "SPI GPIO expanders:"



config GPIO_MAX7301

	tristate "Maxim MAX7301 GPIO expander"

	depends on SPI_MASTER

	help

	  gpio driver for Maxim MAX7301 SPI GPIO expander.



config GPIO_MCP23S08

	tristate "Microchip MCP23S08 I/O expander"

	depends on SPI_MASTER

drivers/gpio/Makefile

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@@ -4,6 +4,7 @@ ccflags-$(CONFIG_DEBUG_GPIO) += -DDEBUG 


obj-$(CONFIG_HAVE_GPIO_LIB)	+= gpiolib.o



obj-$(CONFIG_GPIO_MAX7301)	+= max7301.o

obj-$(CONFIG_GPIO_MCP23S08)	+= mcp23s08.o

obj-$(CONFIG_GPIO_PCA953X)	+= pca953x.o

obj-$(CONFIG_GPIO_PCF857X)	+= pcf857x.o

drivers/gpio/max7301.c

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/**

 * drivers/gpio/max7301.c

 *

 * Copyright (C) 2006 Juergen Beisert, Pengutronix

 * Copyright (C) 2008 Guennadi Liakhovetski, 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's MAX7301 device is an 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/init.h>

#include <linux/platform_device.h>

#include <linux/mutex.h>

#include <linux/spi/spi.h>

#include <linux/spi/max7301.h>

#include <linux/gpio.h>



#define DRIVER_NAME "max7301"



/*

 * 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





/*

 * Some registers must be read back to modify.

 * To save time we cache them here in memory

 */

struct max7301 {

	struct mutex	lock;

	u8		port_config[8];	/* field 0 is unused */

	u32		out_level;	/* cached output levels */

	struct gpio_chip chip;

	struct spi_device *spi;

};



/**

 * max7301_write - Write a new register content

 * @spi: The SPI device

 * @reg: Register offset

 * @val: Value to write

 *

 * A write to the MAX7301 means one message with one transfer

 *

 * Returns 0 if successful or a negative value on error

 */

static int max7301_write(struct spi_device *spi, unsigned int reg, unsigned int val)

{

	u16 word = ((reg & 0x7F) << 8) | (val & 0xFF);

	return spi_write(spi, (const u8 *)&word, sizeof(word));

}



/**

 * max7301_read - Read back register content

 * @spi: The SPI device

 * @reg: Register offset

 *

 * A read from the MAX7301 means two transfers; here, one message each

 *

 * Returns positive 8 bit value from device if successful or a

 * negative value on error

 */

static int max7301_read(struct spi_device *spi, unsigned int reg)

{

	int ret;

	u16 word;



	word = 0x8000 | (reg << 8);

	ret = spi_write(spi, (const u8 *)&word, sizeof(word));

	if (ret)

		return ret;

	/*

	 * This relies on the fact, that a transfer with NULL tx_buf shifts out

	 * zero bytes (=NOOP for MAX7301)

	 */

	ret = spi_read(spi, (u8 *)&word, sizeof(word));

	if (ret)

		return ret;

	return word & 0xff;

}



static int max7301_direction_input(struct gpio_chip *chip, unsigned offset)

{

	struct max7301 *ts = container_of(chip, struct max7301, chip);

	u8 *config;

	int ret;



	/* First 4 pins are unused in the controller */

	offset += 4;



	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 & ~(3 << (offset & 3))) | (1 << (offset & 3));



	ret = max7301_write(ts->spi, 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 max7301_write(ts->spi, 0x20 + offset, 0x01);

	} else {

		ts->out_level &= ~(1 << offset);

		return max7301_write(ts->spi, 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;

	int ret;



	/* First 4 pins are unused in the controller */

	offset += 4;



	config = &ts->port_config[offset >> 2];



	mutex_lock(&ts->lock);



	*config = (*config & ~(3 << (offset & 3))) | (1 << (offset & 3));



	ret = __max7301_set(ts, offset, value);



	if (!ret)

		ret = max7301_write(ts->spi, 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) * 2)) & 3;



	switch (config) {

	case 1:

		/* Output: return cached level */

		level =  !!(ts->out_level & (1 << offset));

		break;

	case 2:

	case 3:

		/* Input: read out */

		level = max7301_read(ts->spi, 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);

}



static int __devinit max7301_probe(struct spi_device *spi)

{

	struct max7301 *ts;

	struct max7301_platform_data *pdata;

	int i, ret;



	pdata = spi->dev.platform_data;

	if (!pdata || !pdata->base)

		return -ENODEV;



	/*

	 * bits_per_word cannot be configured in platform data

	 */

	spi->bits_per_word = 16;



	ret = spi_setup(spi);

	if (ret < 0)

		return ret;



	ts = kzalloc(sizeof(struct max7301), GFP_KERNEL);

	if (!ts)

		return -ENOMEM;



	mutex_init(&ts->lock);



	dev_set_drvdata(&spi->dev, ts);



	/* Power up the chip and disable IRQ output */

	max7301_write(spi, 0x04, 0x01);



	ts->spi = spi;



	ts->chip.label = 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 = &spi->dev;

	ts->chip.owner = THIS_MODULE;



	ret = gpiochip_add(&ts->chip);

	if (ret)

		goto exit_destroy;



	/*

	 * 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 */

		max7301_write(spi, 0x08 + i, 0xAA);

		ts->port_config[i] = 0xAA;

		for (j = 0; j < 4; j++) {

			int idx = ts->chip.base + (i - 1) * 4 + j;

			ret = gpio_direction_input(idx);

			if (ret)

				goto exit_remove;

			gpio_free(idx);

		}

	}

	return ret;



exit_remove:

	gpiochip_remove(&ts->chip);

exit_destroy:

	dev_set_drvdata(&spi->dev, NULL);

	mutex_destroy(&ts->lock);

	kfree(ts);

	return ret;

}



static int max7301_remove(struct spi_device *spi)

{

	struct max7301 *ts;

	int ret;



	ts = dev_get_drvdata(&spi->dev);

	if (ts == NULL)

		return -ENODEV;



	dev_set_drvdata(&spi->dev, NULL);



	/* Power down the chip and disable IRQ output */

	max7301_write(spi, 0x04, 0x00);



	ret = gpiochip_remove(&ts->chip);

	if (!ret) {

		mutex_destroy(&ts->lock);

		kfree(ts);

	} else

		dev_err(&spi->dev, "Failed to remove the GPIO controller: %d\n",

			ret);



	return ret;

}



static struct spi_driver max7301_driver = {

	.driver = {

		.name		= DRIVER_NAME,

		.owner		= THIS_MODULE,

	},

	.probe		= max7301_probe,

	.remove		= __devexit_p(max7301_remove),

};



static int __init max7301_init(void)

{

	return spi_register_driver(&max7301_driver);

}



static void __exit max7301_exit(void)

{

	spi_unregister_driver(&max7301_driver);

}



module_init(max7301_init);

module_exit(max7301_exit);



MODULE_AUTHOR("Juergen Beisert");

MODULE_LICENSE("GPL v2");

MODULE_DESCRIPTION("MAX7301 SPI based GPIO-Expander");

include/linux/spi/max7301.h

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#ifndef LINUX_SPI_MAX7301_H

#define LINUX_SPI_MAX7301_H



struct max7301_platform_data {

	/* number assigned to the first GPIO */

	unsigned	base;

};



#endif

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