From: Juergen Beisert <[email protected]>
Maxim's MAX7301 is an SPI GPIO expander with 28 GPIOs. Note: MAX7301's interrupt
feature is not supported yet.
Signed-off-by: Juergen Beisert <[email protected]>
Signed-off-by: Guennadi Liakhovetski <[email protected]>
---
I know it produces a warning
warning: ignoring return value of 'gpiochip_remove', declared with attribute warn_unused_result
but I really don't see a need to evaluate gpiochip_remove return value at
that place. Maybe it shouldn't be declared with warn_unused_result?
drivers/gpio/Kconfig | 7
drivers/gpio/Makefile | 1
drivers/gpio/max7301.c | 324 ++++++++++++++++++++++++++++++++++++++++++++
include/linux/spi/max7301.h | 9 +
4 files changed, 341 insertions(+)
Index: linux-2.6/drivers/gpio/Kconfig
===================================================================
--- linux-2.6.orig/drivers/gpio/Kconfig 2008-06-05 11:24:20.000000000 +0200
+++ linux-2.6/drivers/gpio/Kconfig 2008-06-05 11:25:24.000000000 +0200
@@ -78,6 +78,12 @@
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
Index: linux-2.6/drivers/gpio/Makefile
===================================================================
--- linux-2.6.orig/drivers/gpio/Makefile 2008-06-05 11:24:20.000000000 +0200
+++ linux-2.6/drivers/gpio/Makefile 2008-06-05 11:25:24.000000000 +0200
@@ -4,6 +4,7 @@
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
Index: linux-2.6/drivers/gpio/max7301.c
===================================================================
--- /dev/null 1970-01-01 00:00:00.000000000 +0000
+++ linux-2.6/drivers/gpio/max7301.c 2008-06-05 11:25:24.000000000 +0200
@@ -0,0 +1,333 @@
+/**
+ * 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 successfull 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 one message with two transfers
+ *
+ * Returns positive 8 bit value from device if successfull 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);
+ if ((ret = spi_write(spi, (const u8*)&word, sizeof(word))) != 0)
+ return ret;
+ /*
+ * FIXME: This read should write 0x0000 (=NOOP at MAX7301 side)
+ */
+ if ((ret = spi_read(spi, (u8*)&word, sizeof(word))))
+ return ret;
+ return word;
+}
+
+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;
+
+ spi->master->setup(spi);
+
+ 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");
Index: linux-2.6/include/linux/spi/max7301.h
===================================================================
--- /dev/null 1970-01-01 00:00:00.000000000 +0000
+++ linux-2.6/include/linux/spi/max7301.h 2008-06-05 11:25:24.000000000 +0200
@@ -0,0 +1,9 @@
+#ifndef LINUX_SPI_MAX7301_H
+#define LINUX_SPI_MAX7301_H
+
+struct max7301_platform_data {
+ /* number assigned to the first GPIO */
+ unsigned base;
+};
+
+#endif
Some comments about one routine; presumably more to follow:
On Friday 06 June 2008, Guennadi Liakhovetski wrote:
> +/**
> + * max7301_read - Read back register content
> + * @spi: The SPI device
> + * @reg: Register offset
> + *
> + * A read from the MAX7301 means one message with two transfers
That's not what you implement though ... what it needs is:
- transfer #1:
* select
* write 16 bit command, discard rx data
* deselect
- transfer #2
* select
* write 16 bit command, saving rx data
* deselect
That's from the data sheet. Now, that *could* be implemented
with a single message ... or, as you do, with two messages.
You should at least correct the comment, if you don't want to
switch to a slightly faster single-message implementation. :)
> + *
> + * Returns positive 8 bit value from device if successfull or a
> + * negative value on error
Actually it returns a 16 bit value... also, "successful" has one "l".
You seem to have forgotten to mask off the high byte ...
> + */
> +static int max7301_read(struct spi_device *spi, unsigned int reg)
> +{
> +???????int ret;
> +???????u16 word;
> +
> +???????word = 0x8000 | (reg << 8);
> +???????if ((ret = spi_write(spi, (const u8*)&word, siz
> eof(word))) != 0)
> +???????????????return ret;
> +???????/*
> +??????? * FIXME: This read should write 0x0000 (=NOOP at MAX7301 side)
Take out this FIXME, and just replace it with a note that this relies
on the fact that TX always shifts out zeroes if there's no data specified.
> +??????? */
> +???????if ((ret = spi_read(spi, (u8*)&word, sizeof(word))))
> +???????????????return ret;
> +???????return word;
> +}
> +
Oh, and in the probe():
> +???????spi->master->setup(spi);
should be
ret = spi_setup(spi);
if (ret < 0)
return ret;
It's quite possible that something get misconfigured, so you end up trying
to talk through a spi_master controller that doesn't support 16-bit words.
- Dave
On Thu, 12 Jun 2008, David Brownell wrote:
> Some comments about one routine; presumably more to follow:
Thanks, David, I'll pass your comments on to the author and try to get
them acted upon.
Thanks
Guennadi
>
>
> On Friday 06 June 2008, Guennadi Liakhovetski wrote:
> > +/**
> > + * max7301_read - Read back register content
> > + * @spi: The SPI device
> > + * @reg: Register offset
> > + *
> > + * A read from the MAX7301 means one message with two transfers
>
> That's not what you implement though ... what it needs is:
>
> - transfer #1:
> * select
> * write 16 bit command, discard rx data
> * deselect
> - transfer #2
> * select
> * write 16 bit command, saving rx data
> * deselect
>
> That's from the data sheet. Now, that *could* be implemented
> with a single message ... or, as you do, with two messages.
>
> You should at least correct the comment, if you don't want to
> switch to a slightly faster single-message implementation. :)
>
>
> > + *
> > + * Returns positive 8 bit value from device if successfull or a
> > + * negative value on error
>
> Actually it returns a 16 bit value... also, "successful" has one "l".
> You seem to have forgotten to mask off the high byte ...
>
>
> > + */
> > +static int max7301_read(struct spi_device *spi, unsigned int reg)
> > +{
> > +???????int ret;
> > +???????u16 word;
> > +
> > +???????word = 0x8000 | (reg << 8);
> > +???????if ((ret = spi_write(spi, (const u8*)&word, siz
>
> > eof(word))) != 0)
> > +???????????????return ret;
> > +???????/*
> > +??????? * FIXME: This read should write 0x0000 (=NOOP at MAX7301 side)
>
> Take out this FIXME, and just replace it with a note that this relies
> on the fact that TX always shifts out zeroes if there's no data specified.
>
> > +??????? */
> > +???????if ((ret = spi_read(spi, (u8*)&word, sizeof(word))))
> > +???????????????return ret;
> > +???????return word;
> > +}
> > +
>
>
> Oh, and in the probe():
>
> > +???????spi->master->setup(spi);
>
> should be
>
> ret = spi_setup(spi);
> if (ret < 0)
> return ret;
>
> It's quite possible that something get misconfigured, so you end up trying
> to talk through a spi_master controller that doesn't support 16-bit words.
>
> - Dave
>
---
Guennadi Liakhovetski, Ph.D.
Freelance Open-Source Software Developer
Fix inaccuracies in comments, check spi_setup() return code, mask off high
byte in max7301_read(). Thanks to David Brownell for the review.
Signed-off-by: Guennadi Liakhovetski <[email protected]>
---
On Thu, 12 Jun 2008, David Brownell wrote:
> Some comments about one routine; presumably more to follow:
Hopefully all points addressed.
Thanks
Guennadi
diff --git a/drivers/gpio/max7301.c b/drivers/gpio/max7301.c
index f35fac5..fc7cebc 100644
--- a/drivers/gpio/max7301.c
+++ b/drivers/gpio/max7301.c
@@ -71,7 +71,7 @@ struct max7301 {
*
* A write to the MAX7301 means one message with one transfer
*
- * Returns 0 if successfull or a negative value on error
+ * Returns 0 if successful or a negative value on error
*/
static int max7301_write(struct spi_device *spi, unsigned int reg, unsigned int val)
{
@@ -84,9 +84,9 @@ static int max7301_write(struct spi_device *spi, unsigned int reg, unsigned int
* @spi: The SPI device
* @reg: Register offset
*
- * A read from the MAX7301 means one message with two transfers
+ * A read from the MAX7301 means two messages with one transfer each
*
- * Returns positive 8 bit value from device if successfull or a
+ * 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)
@@ -99,12 +99,13 @@ static int max7301_read(struct spi_device *spi, unsigned int reg)
if (ret)
return ret;
/*
- * FIXME: This read should write 0x0000 (=NOOP at MAX7301 side)
+ * 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;
+ return word & 0xff;
}
static int max7301_direction_input(struct gpio_chip *chip, unsigned offset)
@@ -224,7 +225,9 @@ static int __devinit max7301_probe(struct spi_device *spi)
*/
spi->bits_per_word = 16;
- spi->master->setup(spi);
+ ret = spi_setup(spi);
+ if (ret < 0)
+ return ret;
ts = kzalloc(sizeof(struct max7301), GFP_KERNEL);
if (!ts)