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remarkable-linux/drivers/gpio/mcp23s08.c
David Brownell 8f1cc3b10e gpio: mcp23s08 handles multiple chips per chipselect 
Teach the mcp23s08 driver about a curious feature of these chips: up to
four of them can share the same chipselect, with the SPI signals wired in
parallel, by matching two bits in the first protocol byte against two
address lines on the chip.

This is handled by three software changes:

  * Platform data now holds an array of per-chip structs, not
    just one chip's address and pullup configuration.

  * Probe() and remove() now use another level of structure,
    wrapping an instance of the original structure for each
    mcp23s08 chip sharing that chipselect.

  * The HAEN bit is set, so that the hardware address bits can no
    longer be ignored (boot firmware may not have enabled them).

The "one struct per chip" preserves the guts of the current code,
but platform_data will need minor changes.

    OLD:
	/* incorrect "slave" ID may not have mattered */
	.slave = 3,
	.pullups = BIT(3) | BIT(1) | BIT(0),

    NEW:
	/* slave address _must_ match chip's wiring */
	.chip[3] = {
		.is_present = true,
		.pullups = BIT(3) | BIT(1) | BIT(0),
	},

There's no change in how things _behave_ for spi_device nodes with a
single mcp23s08 chip.  New multi-chip configurations assign GPIOs in
sequence, without holes.  The spi_device just resembles a bigger
controller, but internally it has multiple gpio_chip instances.

Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-07-25 10:53:30 -07:00

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/*
* mcp23s08.c - SPI gpio expander driver
*/
#include <linux/kernel.h>
#include <linux/device.h>
#include <linux/workqueue.h>
#include <linux/mutex.h>
#include <linux/spi/spi.h>
#include <linux/spi/mcp23s08.h>
#include <asm/gpio.h>
/* Registers are all 8 bits wide.
*
* The mcp23s17 has twice as many bits, and can be configured to work
* with either 16 bit registers or with two adjacent 8 bit banks.
*
* Also, there are I2C versions of both chips.
*/
#define MCP_IODIR 0x00 /* init/reset: all ones */
#define MCP_IPOL 0x01
#define MCP_GPINTEN 0x02
#define MCP_DEFVAL 0x03
#define MCP_INTCON 0x04
#define MCP_IOCON 0x05
# define IOCON_SEQOP (1 << 5)
# define IOCON_HAEN (1 << 3)
# define IOCON_ODR (1 << 2)
# define IOCON_INTPOL (1 << 1)
#define MCP_GPPU 0x06
#define MCP_INTF 0x07
#define MCP_INTCAP 0x08
#define MCP_GPIO 0x09
#define MCP_OLAT 0x0a
struct mcp23s08 {
struct spi_device *spi;
u8 addr;
u8 cache[11];
/* lock protects the cached values */
struct mutex lock;
struct gpio_chip chip;
struct work_struct work;
};
/* A given spi_device can represent up to four mcp23s08 chips
* sharing the same chipselect but using different addresses
* (e.g. chips #0 and #3 might be populated, but not #1 or $2).
* Driver data holds all the per-chip data.
*/
struct mcp23s08_driver_data {
unsigned ngpio;
struct mcp23s08 *mcp[4];
struct mcp23s08 chip[];
};
static int mcp23s08_read(struct mcp23s08 *mcp, unsigned reg)
{
u8 tx[2], rx[1];
int status;
tx[0] = mcp->addr | 0x01;
tx[1] = reg;
status = spi_write_then_read(mcp->spi, tx, sizeof tx, rx, sizeof rx);
return (status < 0) ? status : rx[0];
}
static int mcp23s08_write(struct mcp23s08 *mcp, unsigned reg, u8 val)
{
u8 tx[3];
tx[0] = mcp->addr;
tx[1] = reg;
tx[2] = val;
return spi_write_then_read(mcp->spi, tx, sizeof tx, NULL, 0);
}
static int
mcp23s08_read_regs(struct mcp23s08 *mcp, unsigned reg, u8 *vals, unsigned n)
{
u8 tx[2];
if ((n + reg) > sizeof mcp->cache)
return -EINVAL;
tx[0] = mcp->addr | 0x01;
tx[1] = reg;
return spi_write_then_read(mcp->spi, tx, sizeof tx, vals, n);
}
/*----------------------------------------------------------------------*/
static int mcp23s08_direction_input(struct gpio_chip *chip, unsigned offset)
{
struct mcp23s08 *mcp = container_of(chip, struct mcp23s08, chip);
int status;
mutex_lock(&mcp->lock);
mcp->cache[MCP_IODIR] |= (1 << offset);
status = mcp23s08_write(mcp, MCP_IODIR, mcp->cache[MCP_IODIR]);
mutex_unlock(&mcp->lock);
return status;
}
static int mcp23s08_get(struct gpio_chip *chip, unsigned offset)
{
struct mcp23s08 *mcp = container_of(chip, struct mcp23s08, chip);
int status;
mutex_lock(&mcp->lock);
/* REVISIT reading this clears any IRQ ... */
status = mcp23s08_read(mcp, MCP_GPIO);
if (status < 0)
status = 0;
else {
mcp->cache[MCP_GPIO] = status;
status = !!(status & (1 << offset));
}
mutex_unlock(&mcp->lock);
return status;
}
static int __mcp23s08_set(struct mcp23s08 *mcp, unsigned mask, int value)
{
u8 olat = mcp->cache[MCP_OLAT];
if (value)
olat |= mask;
else
olat &= ~mask;
mcp->cache[MCP_OLAT] = olat;
return mcp23s08_write(mcp, MCP_OLAT, olat);
}
static void mcp23s08_set(struct gpio_chip *chip, unsigned offset, int value)
{
struct mcp23s08 *mcp = container_of(chip, struct mcp23s08, chip);
u8 mask = 1 << offset;
mutex_lock(&mcp->lock);
__mcp23s08_set(mcp, mask, value);
mutex_unlock(&mcp->lock);
}
static int
mcp23s08_direction_output(struct gpio_chip *chip, unsigned offset, int value)
{
struct mcp23s08 *mcp = container_of(chip, struct mcp23s08, chip);
u8 mask = 1 << offset;
int status;
mutex_lock(&mcp->lock);
status = __mcp23s08_set(mcp, mask, value);
if (status == 0) {
mcp->cache[MCP_IODIR] &= ~mask;
status = mcp23s08_write(mcp, MCP_IODIR, mcp->cache[MCP_IODIR]);
}
mutex_unlock(&mcp->lock);
return status;
}
/*----------------------------------------------------------------------*/
#ifdef CONFIG_DEBUG_FS
#include <linux/seq_file.h>
/*
* This shows more info than the generic gpio dump code:
* pullups, deglitching, open drain drive.
*/
static void mcp23s08_dbg_show(struct seq_file *s, struct gpio_chip *chip)
{
struct mcp23s08 *mcp;
char bank;
int t;
unsigned mask;
mcp = container_of(chip, struct mcp23s08, chip);
/* NOTE: we only handle one bank for now ... */
bank = '0' + ((mcp->addr >> 1) & 0x3);
mutex_lock(&mcp->lock);
t = mcp23s08_read_regs(mcp, 0, mcp->cache, sizeof mcp->cache);
if (t < 0) {
seq_printf(s, " I/O ERROR %d\n", t);
goto done;
}
for (t = 0, mask = 1; t < 8; t++, mask <<= 1) {
const char *label;
label = gpiochip_is_requested(chip, t);
if (!label)
continue;
seq_printf(s, " gpio-%-3d P%c.%d (%-12s) %s %s %s",
chip->base + t, bank, t, label,
(mcp->cache[MCP_IODIR] & mask) ? "in " : "out",
(mcp->cache[MCP_GPIO] & mask) ? "hi" : "lo",
(mcp->cache[MCP_GPPU] & mask) ? " " : "up");
/* NOTE: ignoring the irq-related registers */
seq_printf(s, "\n");
}
done:
mutex_unlock(&mcp->lock);
}
#else
#define mcp23s08_dbg_show NULL
#endif
/*----------------------------------------------------------------------*/
static int mcp23s08_probe_one(struct spi_device *spi, unsigned addr,
unsigned base, unsigned pullups)
{
struct mcp23s08_driver_data *data = spi_get_drvdata(spi);
struct mcp23s08 *mcp = data->mcp[addr];
int status;
int do_update = 0;
mutex_init(&mcp->lock);
mcp->spi = spi;
mcp->addr = 0x40 | (addr << 1);
mcp->chip.label = "mcp23s08",
mcp->chip.direction_input = mcp23s08_direction_input;
mcp->chip.get = mcp23s08_get;
mcp->chip.direction_output = mcp23s08_direction_output;
mcp->chip.set = mcp23s08_set;
mcp->chip.dbg_show = mcp23s08_dbg_show;
mcp->chip.base = base;
mcp->chip.ngpio = 8;
mcp->chip.can_sleep = 1;
mcp->chip.dev = &spi->dev;
mcp->chip.owner = THIS_MODULE;
/* verify MCP_IOCON.SEQOP = 0, so sequential reads work,
* and MCP_IOCON.HAEN = 1, so we work with all chips.
*/
status = mcp23s08_read(mcp, MCP_IOCON);
if (status < 0)
goto fail;
if ((status & IOCON_SEQOP) || !(status & IOCON_HAEN)) {
status &= ~IOCON_SEQOP;
status |= IOCON_HAEN;
status = mcp23s08_write(mcp, MCP_IOCON, (u8) status);
if (status < 0)
goto fail;
}
/* configure ~100K pullups */
status = mcp23s08_write(mcp, MCP_GPPU, pullups);
if (status < 0)
goto fail;
status = mcp23s08_read_regs(mcp, 0, mcp->cache, sizeof mcp->cache);
if (status < 0)
goto fail;
/* disable inverter on input */
if (mcp->cache[MCP_IPOL] != 0) {
mcp->cache[MCP_IPOL] = 0;
do_update = 1;
}
/* disable irqs */
if (mcp->cache[MCP_GPINTEN] != 0) {
mcp->cache[MCP_GPINTEN] = 0;
do_update = 1;
}
if (do_update) {
u8 tx[4];
tx[0] = mcp->addr;
tx[1] = MCP_IPOL;
memcpy(&tx[2], &mcp->cache[MCP_IPOL], sizeof(tx) - 2);
status = spi_write_then_read(mcp->spi, tx, sizeof tx, NULL, 0);
if (status < 0)
goto fail;
}
status = gpiochip_add(&mcp->chip);
fail:
if (status < 0)
dev_dbg(&spi->dev, "can't setup chip %d, --> %d\n",
addr, status);
return status;
}
static int mcp23s08_probe(struct spi_device *spi)
{
struct mcp23s08_platform_data *pdata;
unsigned addr;
unsigned chips = 0;
struct mcp23s08_driver_data *data;
int status;
unsigned base;
pdata = spi->dev.platform_data;
if (!pdata || !gpio_is_valid(pdata->base))
return -ENODEV;
for (addr = 0; addr < 4; addr++) {
if (!pdata->chip[addr].is_present)
continue;
chips++;
}
if (!chips)
return -ENODEV;
data = kzalloc(sizeof *data + chips * sizeof(struct mcp23s08),
GFP_KERNEL);
if (!data)
return -ENOMEM;
spi_set_drvdata(spi, data);
base = pdata->base;
for (addr = 0; addr < 4; addr++) {
if (!pdata->chip[addr].is_present)
continue;
chips--;
data->mcp[addr] = &data->chip[chips];
status = mcp23s08_probe_one(spi, addr, base,
pdata->chip[addr].pullups);
if (status < 0)
goto fail;
base += 8;
}
data->ngpio = base - pdata->base;
/* NOTE: these chips have a relatively sane IRQ framework, with
* per-signal masking and level/edge triggering. It's not yet
* handled here...
*/
if (pdata->setup) {
status = pdata->setup(spi,
pdata->base, data->ngpio,
pdata->context);
if (status < 0)
dev_dbg(&spi->dev, "setup --> %d\n", status);
}
return 0;
fail:
for (addr = 0; addr < 4; addr++) {
int tmp;
if (!data->mcp[addr])
continue;
tmp = gpiochip_remove(&data->mcp[addr]->chip);
if (tmp < 0)
dev_err(&spi->dev, "%s --> %d\n", "remove", tmp);
}
kfree(data);
return status;
}
static int mcp23s08_remove(struct spi_device *spi)
{
struct mcp23s08_driver_data *data = spi_get_drvdata(spi);
struct mcp23s08_platform_data *pdata = spi->dev.platform_data;
unsigned addr;
int status = 0;
if (pdata->teardown) {
status = pdata->teardown(spi,
pdata->base, data->ngpio,
pdata->context);
if (status < 0) {
dev_err(&spi->dev, "%s --> %d\n", "teardown", status);
return status;
}
}
for (addr = 0; addr < 4; addr++) {
int tmp;
if (!data->mcp[addr])
continue;
tmp = gpiochip_remove(&data->mcp[addr]->chip);
if (tmp < 0) {
dev_err(&spi->dev, "%s --> %d\n", "remove", tmp);
status = tmp;
}
}
if (status == 0)
kfree(data);
return status;
}
static struct spi_driver mcp23s08_driver = {
.probe = mcp23s08_probe,
.remove = mcp23s08_remove,
.driver = {
.name = "mcp23s08",
.owner = THIS_MODULE,
},
};
/*----------------------------------------------------------------------*/
static int __init mcp23s08_init(void)
{
return spi_register_driver(&mcp23s08_driver);
}
module_init(mcp23s08_init);
static void __exit mcp23s08_exit(void)
{
spi_unregister_driver(&mcp23s08_driver);
}
module_exit(mcp23s08_exit);
MODULE_LICENSE("GPL");
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