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alistair23-linux/drivers/i2c/muxes/i2c-mux-pca954x.c
Robert Shearman f1fb64b04b i2c: mux: pca954x: allow management of device idle state via sysfs 
The behaviour, by default, to not deselect after each transfer is
unsafe when there is a device with an address that conflicts with
another device on another mux on the same parent bus, and it
may not be convenient to use devicetree to set the deselect mux,
e.g. when running on x86_64 when ACPI is used to discover most of the
device hierarchy.

Therefore, provide the ability to set the idle state behaviour using a
new sysfs file, idle_state as a complement to the method of
instantiating the device via sysfs. The possible behaviours are
disconnect, i.e. to deselect all channels from the mux, as-is (the
default), i.e. leave the last channel selected, and set a
predetermined channel.

The current behaviour of leaving the channel as-is after each
transaction is preserved.

Signed-off-by: Robert Shearman <robert.shearman@att.com>
Signed-off-by: Peter Rosin <peda@axentia.se>
2019-04-21 23:44:37 +02:00

557 lines
14 KiB
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/*
* I2C multiplexer
*
* Copyright (c) 2008-2009 Rodolfo Giometti <giometti@linux.it>
* Copyright (c) 2008-2009 Eurotech S.p.A. <info@eurotech.it>
*
* This module supports the PCA954x and PCA954x series of I2C multiplexer/switch
* chips made by NXP Semiconductors.
* This includes the:
* PCA9540, PCA9542, PCA9543, PCA9544, PCA9545, PCA9546, PCA9547,
* PCA9548, PCA9846, PCA9847, PCA9848 and PCA9849.
*
* These chips are all controlled via the I2C bus itself, and all have a
* single 8-bit register. The upstream "parent" bus fans out to two,
* four, or eight downstream busses or channels; which of these
* are selected is determined by the chip type and register contents. A
* mux can select only one sub-bus at a time; a switch can select any
* combination simultaneously.
*
* Based on:
* pca954x.c from Kumar Gala <galak@kernel.crashing.org>
* Copyright (C) 2006
*
* Based on:
* pca954x.c from Ken Harrenstien
* Copyright (C) 2004 Google, Inc. (Ken Harrenstien)
*
* Based on:
* i2c-virtual_cb.c from Brian Kuschak <bkuschak@yahoo.com>
* and
* pca9540.c from Jean Delvare <jdelvare@suse.de>.
*
* This file is licensed under the terms of the GNU General Public
* License version 2. This program is licensed "as is" without any
* warranty of any kind, whether express or implied.
*/
#include <linux/device.h>
#include <linux/delay.h>
#include <linux/gpio/consumer.h>
#include <linux/i2c.h>
#include <linux/i2c-mux.h>
#include <linux/interrupt.h>
#include <linux/irq.h>
#include <linux/module.h>
#include <linux/of.h>
#include <linux/of_device.h>
#include <linux/of_irq.h>
#include <linux/pm.h>
#include <linux/slab.h>
#include <linux/spinlock.h>
#include <dt-bindings/mux/mux.h>
#define PCA954X_MAX_NCHANS 8
#define PCA954X_IRQ_OFFSET 4
enum pca_type {
pca_9540,
pca_9542,
pca_9543,
pca_9544,
pca_9545,
pca_9546,
pca_9547,
pca_9548,
pca_9846,
pca_9847,
pca_9848,
pca_9849,
};
struct chip_desc {
u8 nchans;
u8 enable; /* used for muxes only */
u8 has_irq;
enum muxtype {
pca954x_ismux = 0,
pca954x_isswi
} muxtype;
struct i2c_device_identity id;
};
struct pca954x {
const struct chip_desc *chip;
u8 last_chan; /* last register value */
/* MUX_IDLE_AS_IS, MUX_IDLE_DISCONNECT or >= 0 for channel */
s8 idle_state;
struct i2c_client *client;
struct irq_domain *irq;
unsigned int irq_mask;
raw_spinlock_t lock;
};
/* Provide specs for the PCA954x types we know about */
static const struct chip_desc chips[] = {
[pca_9540] = {
.nchans = 2,
.enable = 0x4,
.muxtype = pca954x_ismux,
.id = { .manufacturer_id = I2C_DEVICE_ID_NONE },
},
[pca_9542] = {
.nchans = 2,
.enable = 0x4,
.has_irq = 1,
.muxtype = pca954x_ismux,
.id = { .manufacturer_id = I2C_DEVICE_ID_NONE },
},
[pca_9543] = {
.nchans = 2,
.has_irq = 1,
.muxtype = pca954x_isswi,
.id = { .manufacturer_id = I2C_DEVICE_ID_NONE },
},
[pca_9544] = {
.nchans = 4,
.enable = 0x4,
.has_irq = 1,
.muxtype = pca954x_ismux,
.id = { .manufacturer_id = I2C_DEVICE_ID_NONE },
},
[pca_9545] = {
.nchans = 4,
.has_irq = 1,
.muxtype = pca954x_isswi,
.id = { .manufacturer_id = I2C_DEVICE_ID_NONE },
},
[pca_9546] = {
.nchans = 4,
.muxtype = pca954x_isswi,
.id = { .manufacturer_id = I2C_DEVICE_ID_NONE },
},
[pca_9547] = {
.nchans = 8,
.enable = 0x8,
.muxtype = pca954x_ismux,
.id = { .manufacturer_id = I2C_DEVICE_ID_NONE },
},
[pca_9548] = {
.nchans = 8,
.muxtype = pca954x_isswi,
.id = { .manufacturer_id = I2C_DEVICE_ID_NONE },
},
[pca_9846] = {
.nchans = 4,
.muxtype = pca954x_isswi,
.id = {
.manufacturer_id = I2C_DEVICE_ID_NXP_SEMICONDUCTORS,
.part_id = 0x10b,
},
},
[pca_9847] = {
.nchans = 8,
.enable = 0x8,
.muxtype = pca954x_ismux,
.id = {
.manufacturer_id = I2C_DEVICE_ID_NXP_SEMICONDUCTORS,
.part_id = 0x108,
},
},
[pca_9848] = {
.nchans = 8,
.muxtype = pca954x_isswi,
.id = {
.manufacturer_id = I2C_DEVICE_ID_NXP_SEMICONDUCTORS,
.part_id = 0x10a,
},
},
[pca_9849] = {
.nchans = 4,
.enable = 0x4,
.muxtype = pca954x_ismux,
.id = {
.manufacturer_id = I2C_DEVICE_ID_NXP_SEMICONDUCTORS,
.part_id = 0x109,
},
},
};
static const struct i2c_device_id pca954x_id[] = {
{ "pca9540", pca_9540 },
{ "pca9542", pca_9542 },
{ "pca9543", pca_9543 },
{ "pca9544", pca_9544 },
{ "pca9545", pca_9545 },
{ "pca9546", pca_9546 },
{ "pca9547", pca_9547 },
{ "pca9548", pca_9548 },
{ "pca9846", pca_9846 },
{ "pca9847", pca_9847 },
{ "pca9848", pca_9848 },
{ "pca9849", pca_9849 },
{ }
};
MODULE_DEVICE_TABLE(i2c, pca954x_id);
#ifdef CONFIG_OF
static const struct of_device_id pca954x_of_match[] = {
{ .compatible = "nxp,pca9540", .data = &chips[pca_9540] },
{ .compatible = "nxp,pca9542", .data = &chips[pca_9542] },
{ .compatible = "nxp,pca9543", .data = &chips[pca_9543] },
{ .compatible = "nxp,pca9544", .data = &chips[pca_9544] },
{ .compatible = "nxp,pca9545", .data = &chips[pca_9545] },
{ .compatible = "nxp,pca9546", .data = &chips[pca_9546] },
{ .compatible = "nxp,pca9547", .data = &chips[pca_9547] },
{ .compatible = "nxp,pca9548", .data = &chips[pca_9548] },
{ .compatible = "nxp,pca9846", .data = &chips[pca_9846] },
{ .compatible = "nxp,pca9847", .data = &chips[pca_9847] },
{ .compatible = "nxp,pca9848", .data = &chips[pca_9848] },
{ .compatible = "nxp,pca9849", .data = &chips[pca_9849] },
{}
};
MODULE_DEVICE_TABLE(of, pca954x_of_match);
#endif
/* Write to mux register. Don't use i2c_transfer()/i2c_smbus_xfer()
for this as they will try to lock adapter a second time */
static int pca954x_reg_write(struct i2c_adapter *adap,
struct i2c_client *client, u8 val)
{
union i2c_smbus_data dummy;
return __i2c_smbus_xfer(adap, client->addr, client->flags,
I2C_SMBUS_WRITE, val,
I2C_SMBUS_BYTE, &dummy);
}
static int pca954x_select_chan(struct i2c_mux_core *muxc, u32 chan)
{
struct pca954x *data = i2c_mux_priv(muxc);
struct i2c_client *client = data->client;
const struct chip_desc *chip = data->chip;
u8 regval;
int ret = 0;
/* we make switches look like muxes, not sure how to be smarter */
if (chip->muxtype == pca954x_ismux)
regval = chan | chip->enable;
else
regval = 1 << chan;
/* Only select the channel if its different from the last channel */
if (data->last_chan != regval) {
ret = pca954x_reg_write(muxc->parent, client, regval);
data->last_chan = ret < 0 ? 0 : regval;
}
return ret;
}
static int pca954x_deselect_mux(struct i2c_mux_core *muxc, u32 chan)
{
struct pca954x *data = i2c_mux_priv(muxc);
struct i2c_client *client = data->client;
s8 idle_state;
idle_state = READ_ONCE(data->idle_state);
if (idle_state >= 0)
/* Set the mux back to a predetermined channel */
return pca954x_select_chan(muxc, idle_state);
if (idle_state == MUX_IDLE_DISCONNECT) {
/* Deselect active channel */
data->last_chan = 0;
return pca954x_reg_write(muxc->parent, client,
data->last_chan);
}
/* otherwise leave as-is */
return 0;
}
static ssize_t idle_state_show(struct device *dev,
struct device_attribute *attr,
char *buf)
{
struct i2c_client *client = to_i2c_client(dev);
struct i2c_mux_core *muxc = i2c_get_clientdata(client);
struct pca954x *data = i2c_mux_priv(muxc);
return sprintf(buf, "%d\n", READ_ONCE(data->idle_state));
}
static ssize_t idle_state_store(struct device *dev,
struct device_attribute *attr,
const char *buf, size_t count)
{
struct i2c_client *client = to_i2c_client(dev);
struct i2c_mux_core *muxc = i2c_get_clientdata(client);
struct pca954x *data = i2c_mux_priv(muxc);
int val;
int ret;
ret = kstrtoint(buf, 0, &val);
if (ret < 0)
return ret;
if (val != MUX_IDLE_AS_IS && val != MUX_IDLE_DISCONNECT &&
(val < 0 || val >= data->chip->nchans))
return -EINVAL;
i2c_lock_bus(muxc->parent, I2C_LOCK_SEGMENT);
WRITE_ONCE(data->idle_state, val);
/*
* Set the mux into a state consistent with the new
* idle_state.
*/
if (data->last_chan || val != MUX_IDLE_DISCONNECT)
ret = pca954x_deselect_mux(muxc, 0);
i2c_unlock_bus(muxc->parent, I2C_LOCK_SEGMENT);
return ret < 0 ? ret : count;
}
static DEVICE_ATTR_RW(idle_state);
static irqreturn_t pca954x_irq_handler(int irq, void *dev_id)
{
struct pca954x *data = dev_id;
unsigned int child_irq;
int ret, i, handled = 0;
ret = i2c_smbus_read_byte(data->client);
if (ret < 0)
return IRQ_NONE;
for (i = 0; i < data->chip->nchans; i++) {
if (ret & BIT(PCA954X_IRQ_OFFSET + i)) {
child_irq = irq_linear_revmap(data->irq, i);
handle_nested_irq(child_irq);
handled++;
}
}
return handled ? IRQ_HANDLED : IRQ_NONE;
}
static int pca954x_irq_set_type(struct irq_data *idata, unsigned int type)
{
if ((type & IRQ_TYPE_SENSE_MASK) != IRQ_TYPE_LEVEL_LOW)
return -EINVAL;
return 0;
}
static struct irq_chip pca954x_irq_chip = {
.name = "i2c-mux-pca954x",
.irq_set_type = pca954x_irq_set_type,
};
static int pca954x_irq_setup(struct i2c_mux_core *muxc)
{
struct pca954x *data = i2c_mux_priv(muxc);
struct i2c_client *client = data->client;
int c, irq;
if (!data->chip->has_irq || client->irq <= 0)
return 0;
raw_spin_lock_init(&data->lock);
data->irq = irq_domain_add_linear(client->dev.of_node,
data->chip->nchans,
&irq_domain_simple_ops, data);
if (!data->irq)
return -ENODEV;
for (c = 0; c < data->chip->nchans; c++) {
irq = irq_create_mapping(data->irq, c);
if (!irq) {
dev_err(&client->dev, "failed irq create map\n");
return -EINVAL;
}
irq_set_chip_data(irq, data);
irq_set_chip_and_handler(irq, &pca954x_irq_chip,
handle_simple_irq);
}
return 0;
}
static void pca954x_cleanup(struct i2c_mux_core *muxc)
{
struct pca954x *data = i2c_mux_priv(muxc);
struct i2c_client *client = data->client;
int c, irq;
device_remove_file(&client->dev, &dev_attr_idle_state);
if (data->irq) {
for (c = 0; c < data->chip->nchans; c++) {
irq = irq_find_mapping(data->irq, c);
irq_dispose_mapping(irq);
}
irq_domain_remove(data->irq);
}
i2c_mux_del_adapters(muxc);
}
/*
* I2C init/probing/exit functions
*/
static int pca954x_probe(struct i2c_client *client,
const struct i2c_device_id *id)
{
struct i2c_adapter *adap = client->adapter;
struct device *dev = &client->dev;
struct device_node *np = dev->of_node;
bool idle_disconnect_dt;
struct gpio_desc *gpio;
struct i2c_mux_core *muxc;
struct pca954x *data;
int num;
int ret;
if (!i2c_check_functionality(adap, I2C_FUNC_SMBUS_BYTE))
return -ENODEV;
muxc = i2c_mux_alloc(adap, dev, PCA954X_MAX_NCHANS, sizeof(*data), 0,
pca954x_select_chan, pca954x_deselect_mux);
if (!muxc)
return -ENOMEM;
data = i2c_mux_priv(muxc);
i2c_set_clientdata(client, muxc);
data->client = client;
/* Reset the mux if a reset GPIO is specified. */
gpio = devm_gpiod_get_optional(dev, "reset", GPIOD_OUT_HIGH);
if (IS_ERR(gpio))
return PTR_ERR(gpio);
if (gpio) {
udelay(1);
gpiod_set_value_cansleep(gpio, 0);
/* Give the chip some time to recover. */
udelay(1);
}
data->chip = of_device_get_match_data(dev);
if (!data->chip)
data->chip = &chips[id->driver_data];
if (data->chip->id.manufacturer_id != I2C_DEVICE_ID_NONE) {
struct i2c_device_identity id;
ret = i2c_get_device_id(client, &id);
if (ret && ret != -EOPNOTSUPP)
return ret;
if (!ret &&
(id.manufacturer_id != data->chip->id.manufacturer_id ||
id.part_id != data->chip->id.part_id)) {
dev_warn(dev, "unexpected device id %03x-%03x-%x\n",
id.manufacturer_id, id.part_id,
id.die_revision);
return -ENODEV;
}
}
/* Write the mux register at addr to verify
* that the mux is in fact present. This also
* initializes the mux to disconnected state.
*/
if (i2c_smbus_write_byte(client, 0) < 0) {
dev_warn(dev, "probe failed\n");
return -ENODEV;
}
data->last_chan = 0; /* force the first selection */
data->idle_state = MUX_IDLE_AS_IS;
idle_disconnect_dt = np &&
of_property_read_bool(np, "i2c-mux-idle-disconnect");
if (idle_disconnect_dt)
data->idle_state = MUX_IDLE_DISCONNECT;
ret = pca954x_irq_setup(muxc);
if (ret)
goto fail_cleanup;
/* Now create an adapter for each channel */
for (num = 0; num < data->chip->nchans; num++) {
ret = i2c_mux_add_adapter(muxc, 0, num, 0);
if (ret)
goto fail_cleanup;
}
if (data->irq) {
ret = devm_request_threaded_irq(dev, data->client->irq,
NULL, pca954x_irq_handler,
IRQF_ONESHOT | IRQF_SHARED,
"pca954x", data);
if (ret)
goto fail_cleanup;
}
/*
* The attr probably isn't going to be needed in most cases,
* so don't fail completely on error.
*/
device_create_file(dev, &dev_attr_idle_state);
dev_info(dev, "registered %d multiplexed busses for I2C %s %s\n",
num, data->chip->muxtype == pca954x_ismux
? "mux" : "switch", client->name);
return 0;
fail_cleanup:
pca954x_cleanup(muxc);
return ret;
}
static int pca954x_remove(struct i2c_client *client)
{
struct i2c_mux_core *muxc = i2c_get_clientdata(client);
pca954x_cleanup(muxc);
return 0;
}
#ifdef CONFIG_PM_SLEEP
static int pca954x_resume(struct device *dev)
{
struct i2c_client *client = to_i2c_client(dev);
struct i2c_mux_core *muxc = i2c_get_clientdata(client);
struct pca954x *data = i2c_mux_priv(muxc);
data->last_chan = 0;
return i2c_smbus_write_byte(client, 0);
}
#endif
static SIMPLE_DEV_PM_OPS(pca954x_pm, NULL, pca954x_resume);
static struct i2c_driver pca954x_driver = {
.driver = {
.name = "pca954x",
.pm = &pca954x_pm,
.of_match_table = of_match_ptr(pca954x_of_match),
},
.probe = pca954x_probe,
.remove = pca954x_remove,
.id_table = pca954x_id,
};
module_i2c_driver(pca954x_driver);
MODULE_AUTHOR("Rodolfo Giometti <giometti@linux.it>");
MODULE_DESCRIPTION("PCA954x I2C mux/switch driver");
MODULE_LICENSE("GPL v2");
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