diff options
Diffstat (limited to 'drivers/i2c/busses/i2c-gpio.c')
| -rw-r--r-- | drivers/i2c/busses/i2c-gpio.c | 524 |
1 files changed, 524 insertions, 0 deletions
diff --git a/drivers/i2c/busses/i2c-gpio.c b/drivers/i2c/busses/i2c-gpio.c new file mode 100644 index 000000000..b1985c166 --- /dev/null +++ b/drivers/i2c/busses/i2c-gpio.c @@ -0,0 +1,524 @@ +// 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 CONFIG_I2C_GPIO_FAULT_INJECTOR + 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 CONFIG_I2C_GPIO_FAULT_INJECTOR +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 (PTR_ERR(retdesc) != -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) + strscpy(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(CONFIG_OF) +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 v2"); +MODULE_ALIAS("platform:i2c-gpio"); |