// SPDX-License-Identifier: GPL-2.0-only
/*
* Bitbanging I2C bus driver using the GPIO API
*
* Copyright (C) 2007 Atmel Corporation
*/
#include <linux/completion.h>
#include <linux/debugfs.h>
#include <linux/delay.h>
#include <linux/gpio/consumer.h>
#include <linux/i2c-algo-bit.h>
#include <linux/i2c.h>
#include <linux/init.h>
#include <linux/interrupt.h>
#include <linux/module.h>
#include <linux/of.h>
#include <linux/platform_data/i2c-gpio.h>
#include <linux/platform_device.h>
#include <linux/slab.h>
struct i2c_gpio_private_data {
struct gpio_desc *sda;
struct gpio_desc *scl;
struct i2c_adapter adap;
struct i2c_algo_bit_data bit_data;
struct i2c_gpio_platform_data pdata;
#ifdef [31mCONFIG_I2C_GPIO_FAULT_INJECTOR[0m
struct dentry *debug_dir;
/* these must be protected by bus lock */
struct completion scl_irq_completion;
u64 scl_irq_data;
#endif
};
/*
* Toggle SDA by changing the output value of the pin. This is only
* valid for pins configured as open drain (i.e. setting the value
* high effectively turns off the output driver.)
*/
static void i2c_gpio_setsda_val(void *data, int state)
{
struct i2c_gpio_private_data *priv = data;
gpiod_set_value_cansleep(priv->sda, state);
}
/*
* Toggle SCL by changing the output value of the pin. This is used
* for pins that are configured as open drain and for output-only
* pins. The latter case will break the i2c protocol, but it will
* often work in practice.
*/
static void i2c_gpio_setscl_val(void *data, int state)
{
struct i2c_gpio_private_data *priv = data;
gpiod_set_value_cansleep(priv->scl, state);
}
static int i2c_gpio_getsda(void *data)
{
struct i2c_gpio_private_data *priv = data;
return gpiod_get_value_cansleep(priv->sda);
}
static int i2c_gpio_getscl(void *data)
{
struct i2c_gpio_private_data *priv = data;
return gpiod_get_value_cansleep(priv->scl);
}
#ifdef [31mCONFIG_I2C_GPIO_FAULT_INJECTOR[0m
static struct dentry *i2c_gpio_debug_dir;
#define setsda(bd, val) ((bd)->setsda((bd)->data, val))
#define setscl(bd, val) ((bd)->setscl((bd)->data, val))
#define getsda(bd) ((bd)->getsda((bd)->data))
#define getscl(bd) ((bd)->getscl((bd)->data))
#define WIRE_ATTRIBUTE(wire) \
static int fops_##wire##_get(void *data, u64 *val) \
{ \
struct i2c_gpio_private_data *priv = data; \
\
i2c_lock_bus(&priv->adap, I2C_LOCK_ROOT_ADAPTER); \
*val = get##wire(&priv->bit_data); \
i2c_unlock_bus(&priv->adap, I2C_LOCK_ROOT_ADAPTER); \
return 0; \
} \
static int fops_##wire##_set(void *data, u64 val) \
{ \
struct i2c_gpio_private_data *priv = data; \
\
i2c_lock_bus(&priv->adap, I2C_LOCK_ROOT_ADAPTER); \
set##wire(&priv->bit_data, val); \
i2c_unlock_bus(&priv->adap, I2C_LOCK_ROOT_ADAPTER); \
return 0; \
} \
DEFINE_DEBUGFS_ATTRIBUTE(fops_##wire, fops_##wire##_get, fops_##wire##_set, "%llu\n")
WIRE_ATTRIBUTE(scl);
WIRE_ATTRIBUTE(sda);
static void i2c_gpio_incomplete_transfer(struct i2c_gpio_private_data *priv,
u32 pattern, u8 pattern_size)
{
struct i2c_algo_bit_data *bit_data = &priv->bit_data;
int i;
i2c_lock_bus(&priv->adap, I2C_LOCK_ROOT_ADAPTER);
/* START condition */
setsda(bit_data, 0);
udelay(bit_data->udelay);
/* Send pattern, request ACK, don't send STOP */
for (i = pattern_size - 1; i >= 0; i--) {
setscl(bit_data, 0);
udelay(bit_data->udelay / 2);
setsda(bit_data, (pattern >> i) & 1);
udelay((bit_data->udelay + 1) / 2);
setscl(bit_data, 1);
udelay(bit_data->udelay);
}
i2c_unlock_bus(&priv->adap, I2C_LOCK_ROOT_ADAPTER);
}
static int fops_incomplete_addr_phase_set(void *data, u64 addr)
{
struct i2c_gpio_private_data *priv = data;
u32 pattern;
if (addr > 0x7f)
return -EINVAL;
/* ADDR (7 bit) + RD (1 bit) + Client ACK, keep SDA hi (1 bit) */
pattern = (addr << 2) | 3;
i2c_gpio_incomplete_transfer(priv, pattern, 9);
return 0;
}
DEFINE_DEBUGFS_ATTRIBUTE(fops_incomplete_addr_phase, NULL, fops_incomplete_addr_phase_set, "%llu\n");
static int fops_incomplete_write_byte_set(void *data, u64 addr)
{
struct i2c_gpio_private_data *priv = data;
u32 pattern;
if (addr > 0x7f)
return -EINVAL;
/* ADDR (7 bit) + WR (1 bit) + Client ACK (1 bit) */
pattern = (addr << 2) | 1;
/* 0x00 (8 bit) + Client ACK, keep SDA hi (1 bit) */
pattern = (pattern << 9) | 1;
i2c_gpio_incomplete_transfer(priv, pattern, 18);
return 0;
}
DEFINE_DEBUGFS_ATTRIBUTE(fops_incomplete_write_byte, NULL, fops_incomplete_write_byte_set, "%llu\n");
static int i2c_gpio_fi_act_on_scl_irq(struct i2c_gpio_private_data *priv,
irqreturn_t handler(int, void*))
{
int ret, irq = gpiod_to_irq(priv->scl);
if (irq < 0)
return irq;
i2c_lock_bus(&priv->adap, I2C_LOCK_ROOT_ADAPTER);
ret = gpiod_direction_input(priv->scl);
if (ret)
goto unlock;
reinit_completion(&priv->scl_irq_completion);
ret = request_irq(irq, handler, IRQF_TRIGGER_FALLING,
"i2c_gpio_fault_injector_scl_irq", priv);
if (ret)
goto output;
wait_for_completion_interruptible(&priv->scl_irq_completion);
free_irq(irq, priv);
output:
ret = gpiod_direction_output(priv->scl, 1) ?: ret;
unlock:
i2c_unlock_bus(&priv->adap, I2C_LOCK_ROOT_ADAPTER);
return ret;
}
static irqreturn_t lose_arbitration_irq(int irq, void *dev_id)
{
struct i2c_gpio_private_data *priv = dev_id;
setsda(&priv->bit_data, 0);
udelay(priv->scl_irq_data);
setsda(&priv->bit_data, 1);
complete(&priv->scl_irq_completion);
return IRQ_HANDLED;
}
static int fops_lose_arbitration_set(void *data, u64 duration)
{
struct i2c_gpio_private_data *priv = data;
if (duration > 100 * 1000)
return -EINVAL;
priv->scl_irq_data = duration;
/*
* Interrupt on falling SCL. This ensures that the master under test has
* really started the transfer. Interrupt on falling SDA did only
* exercise 'bus busy' detection on some HW but not 'arbitration lost'.
* Note that the interrupt latency may cause the first bits to be
* transmitted correctly.
*/
return i2c_gpio_fi_act_on_scl_irq(priv, lose_arbitration_irq);
}
DEFINE_DEBUGFS_ATTRIBUTE(fops_lose_arbitration, NULL, fops_lose_arbitration_set, "%llu\n");
static irqreturn_t inject_panic_irq(int irq, void *dev_id)
{
struct i2c_gpio_private_data *priv = dev_id;
udelay(priv->scl_irq_data);
panic("I2C fault injector induced panic");
return IRQ_HANDLED;
}
static int fops_inject_panic_set(void *data, u64 duration)
{
struct i2c_gpio_private_data *priv = data;
if (duration > 100 * 1000)
return -EINVAL;
priv->scl_irq_data = duration;
/*
* Interrupt on falling SCL. This ensures that the master under test has
* really started the transfer.
*/
return i2c_gpio_fi_act_on_scl_irq(priv, inject_panic_irq);
}
DEFINE_DEBUGFS_ATTRIBUTE(fops_inject_panic, NULL, fops_inject_panic_set, "%llu\n");
static void i2c_gpio_fault_injector_init(struct platform_device *pdev)
{
struct i2c_gpio_private_data *priv = platform_get_drvdata(pdev);
/*
* If there will be a debugfs-dir per i2c adapter somewhen, put the
* 'fault-injector' dir there. Until then, we have a global dir with
* all adapters as subdirs.
*/
if (!i2c_gpio_debug_dir) {
i2c_gpio_debug_dir = debugfs_create_dir("i2c-fault-injector", NULL);
if (!i2c_gpio_debug_dir)
return;
}
priv->debug_dir = debugfs_create_dir(pdev->name, i2c_gpio_debug_dir);
if (!priv->debug_dir)
return;
init_completion(&priv->scl_irq_completion);
debugfs_create_file_unsafe("incomplete_address_phase", 0200, priv->debug_dir,
priv, &fops_incomplete_addr_phase);
debugfs_create_file_unsafe("incomplete_write_byte", 0200, priv->debug_dir,
priv, &fops_incomplete_write_byte);
if (priv->bit_data.getscl) {
debugfs_create_file_unsafe("inject_panic", 0200, priv->debug_dir,
priv, &fops_inject_panic);
debugfs_create_file_unsafe("lose_arbitration", 0200, priv->debug_dir,
priv, &fops_lose_arbitration);
}
debugfs_create_file_unsafe("scl", 0600, priv->debug_dir, priv, &fops_scl);
debugfs_create_file_unsafe("sda", 0600, priv->debug_dir, priv, &fops_sda);
}
static void i2c_gpio_fault_injector_exit(struct platform_device *pdev)
{
struct i2c_gpio_private_data *priv = platform_get_drvdata(pdev);
debugfs_remove_recursive(priv->debug_dir);
}
#else
static inline void i2c_gpio_fault_injector_init(struct platform_device *pdev) {}
static inline void i2c_gpio_fault_injector_exit(struct platform_device *pdev) {}
#endif /* CONFIG_I2C_GPIO_FAULT_INJECTOR*/
static void of_i2c_gpio_get_props(struct device_node *np,
struct i2c_gpio_platform_data *pdata)
{
u32 reg;
of_property_read_u32(np, "i2c-gpio,delay-us", &pdata->udelay);
if (!of_property_read_u32(np, "i2c-gpio,timeout-ms", ®))
pdata->timeout = msecs_to_jiffies(reg);
pdata->sda_is_open_drain =
of_property_read_bool(np, "i2c-gpio,sda-open-drain");
pdata->scl_is_open_drain =
of_property_read_bool(np, "i2c-gpio,scl-open-drain");
pdata->scl_is_output_only =
of_property_read_bool(np, "i2c-gpio,scl-output-only");
}
static struct gpio_desc *i2c_gpio_get_desc(struct device *dev,
const char *con_id,
unsigned int index,
enum gpiod_flags gflags)
{
struct gpio_desc *retdesc;
int ret;
retdesc = devm_gpiod_get(dev, con_id, gflags);
if (!IS_ERR(retdesc)) {
dev_dbg(dev, "got GPIO from name %s\n", con_id);
return retdesc;
}
retdesc = devm_gpiod_get_index(dev, NULL, index, gflags);
if (!IS_ERR(retdesc)) {
dev_dbg(dev, "got GPIO from index %u\n", index);
return retdesc;
}
ret = PTR_ERR(retdesc);
/* FIXME: hack in the old code, is this really necessary? */
if (ret == -EINVAL)
retdesc = ERR_PTR(-EPROBE_DEFER);
/* This happens if the GPIO driver is not yet probed, let's defer */
if (ret == -ENOENT)
retdesc = ERR_PTR(-EPROBE_DEFER);
if (ret != -EPROBE_DEFER)
dev_err(dev, "error trying to get descriptor: %d\n", ret);
return retdesc;
}
static int i2c_gpio_probe(struct platform_device *pdev)
{
struct i2c_gpio_private_data *priv;
struct i2c_gpio_platform_data *pdata;
struct i2c_algo_bit_data *bit_data;
struct i2c_adapter *adap;
struct device *dev = &pdev->dev;
struct device_node *np = dev->of_node;
enum gpiod_flags gflags;
int ret;
priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
if (!priv)
return -ENOMEM;
adap = &priv->adap;
bit_data = &priv->bit_data;
pdata = &priv->pdata;
if (np) {
of_i2c_gpio_get_props(np, pdata);
} else {
/*
* If all platform data settings are zero it is OK
* to not provide any platform data from the board.
*/
if (dev_get_platdata(dev))
memcpy(pdata, dev_get_platdata(dev), sizeof(*pdata));
}
/*
* First get the GPIO pins; if it fails, we'll defer the probe.
* If the SCL/SDA lines are marked "open drain" by platform data or
* device tree then this means that something outside of our control is
* marking these lines to be handled as open drain, and we should just
* handle them as we handle any other output. Else we enforce open
* drain as this is required for an I2C bus.
*/
if (pdata->sda_is_open_drain)
gflags = GPIOD_OUT_HIGH;
else
gflags = GPIOD_OUT_HIGH_OPEN_DRAIN;
priv->sda = i2c_gpio_get_desc(dev, "sda", 0, gflags);
if (IS_ERR(priv->sda))
return PTR_ERR(priv->sda);
if (pdata->scl_is_open_drain)
gflags = GPIOD_OUT_HIGH;
else
gflags = GPIOD_OUT_HIGH_OPEN_DRAIN;
priv->scl = i2c_gpio_get_desc(dev, "scl", 1, gflags);
if (IS_ERR(priv->scl))
return PTR_ERR(priv->scl);
if (gpiod_cansleep(priv->sda) || gpiod_cansleep(priv->scl))
dev_warn(dev, "Slow GPIO pins might wreak havoc into I2C/SMBus bus timing");
else
bit_data->can_do_atomic = true;
bit_data->setsda = i2c_gpio_setsda_val;
bit_data->setscl = i2c_gpio_setscl_val;
if (!pdata->scl_is_output_only)
bit_data->getscl = i2c_gpio_getscl;
bit_data->getsda = i2c_gpio_getsda;
if (pdata->udelay)
bit_data->udelay = pdata->udelay;
else if (pdata->scl_is_output_only)
bit_data->udelay = 50; /* 10 kHz */
else
bit_data->udelay = 5; /* 100 kHz */
if (pdata->timeout)
bit_data->timeout = pdata->timeout;
else
bit_data->timeout = HZ / 10; /* 100 ms */
bit_data->data = priv;
adap->owner = THIS_MODULE;
if (np)
strlcpy(adap->name, dev_name(dev), sizeof(adap->name));
else
snprintf(adap->name, sizeof(adap->name), "i2c-gpio%d", pdev->id);
adap->algo_data = bit_data;
adap->class = I2C_CLASS_HWMON | I2C_CLASS_SPD;
adap->dev.parent = dev;
adap->dev.of_node = np;
adap->nr = pdev->id;
ret = i2c_bit_add_numbered_bus(adap);
if (ret)
return ret;
platform_set_drvdata(pdev, priv);
/*
* FIXME: using global GPIO numbers is not helpful. If/when we
* get accessors to get the actual name of the GPIO line,
* from the descriptor, then provide that instead.
*/
dev_info(dev, "using lines %u (SDA) and %u (SCL%s)\n",
desc_to_gpio(priv->sda), desc_to_gpio(priv->scl),
pdata->scl_is_output_only
? ", no clock stretching" : "");
i2c_gpio_fault_injector_init(pdev);
return 0;
}
static int i2c_gpio_remove(struct platform_device *pdev)
{
struct i2c_gpio_private_data *priv;
struct i2c_adapter *adap;
i2c_gpio_fault_injector_exit(pdev);
priv = platform_get_drvdata(pdev);
adap = &priv->adap;
i2c_del_adapter(adap);
return 0;
}
#if defined([31mCONFIG_OF[0m)
static const struct of_device_id i2c_gpio_dt_ids[] = {
{ .compatible = "i2c-gpio", },
{ /* sentinel */ }
};
MODULE_DEVICE_TABLE(of, i2c_gpio_dt_ids);
#endif
static struct platform_driver i2c_gpio_driver = {
.driver = {
.name = "i2c-gpio",
.of_match_table = of_match_ptr(i2c_gpio_dt_ids),
},
.probe = i2c_gpio_probe,
.remove = i2c_gpio_remove,
};
static int __init i2c_gpio_init(void)
{
int ret;
ret = platform_driver_register(&i2c_gpio_driver);
if (ret)
printk(KERN_ERR "i2c-gpio: probe failed: %d\n", ret);
return ret;
}
subsys_initcall(i2c_gpio_init);
static void __exit i2c_gpio_exit(void)
{
platform_driver_unregister(&i2c_gpio_driver);
}
module_exit(i2c_gpio_exit);
MODULE_AUTHOR("Haavard Skinnemoen (Atmel)");
MODULE_DESCRIPTION("Platform-independent bitbanging I2C driver");
MODULE_LICENSE("GPL");
MODULE_ALIAS("platform:i2c-gpio");