| // 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/platform_data/i2c-gpio.h> |
| #include <linux/platform_device.h> |
| #include <linux/property.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*/ |
| |
| /* Get i2c-gpio properties from DT or ACPI table */ |
| static void i2c_gpio_get_properties(struct device *dev, |
| struct i2c_gpio_platform_data *pdata) |
| { |
| u32 reg; |
| |
| device_property_read_u32(dev, "i2c-gpio,delay-us", &pdata->udelay); |
| |
| if (!device_property_read_u32(dev, "i2c-gpio,timeout-ms", ®)) |
| pdata->timeout = msecs_to_jiffies(reg); |
| |
| pdata->sda_is_open_drain = |
| device_property_read_bool(dev, "i2c-gpio,sda-open-drain"); |
| pdata->scl_is_open_drain = |
| device_property_read_bool(dev, "i2c-gpio,scl-open-drain"); |
| pdata->scl_is_output_only = |
| device_property_read_bool(dev, "i2c-gpio,scl-output-only"); |
| pdata->sda_is_output_only = |
| device_property_read_bool(dev, "i2c-gpio,sda-output-only"); |
| pdata->sda_has_no_pullup = |
| device_property_read_bool(dev, "i2c-gpio,sda-has-no-pullup"); |
| pdata->scl_has_no_pullup = |
| device_property_read_bool(dev, "i2c-gpio,scl-has-no-pullup"); |
| } |
| |
| 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 fwnode_handle *fwnode = dev_fwnode(dev); |
| 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 (fwnode) { |
| i2c_gpio_get_properties(dev, 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 || pdata->sda_has_no_pullup) |
| 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 || pdata->scl_has_no_pullup) |
| 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; |
| if (!pdata->sda_is_output_only) |
| 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 (fwnode) |
| 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; |
| device_set_node(&adap->dev, fwnode); |
| |
| 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; |
| } |
| |
| static const struct of_device_id i2c_gpio_dt_ids[] = { |
| { .compatible = "i2c-gpio", }, |
| { /* sentinel */ } |
| }; |
| |
| MODULE_DEVICE_TABLE(of, i2c_gpio_dt_ids); |
| |
| static const struct acpi_device_id i2c_gpio_acpi_match[] = { |
| { "LOON0005" }, /* LoongArch */ |
| { } |
| }; |
| MODULE_DEVICE_TABLE(acpi, i2c_gpio_acpi_match); |
| |
| static struct platform_driver i2c_gpio_driver = { |
| .driver = { |
| .name = "i2c-gpio", |
| .of_match_table = i2c_gpio_dt_ids, |
| .acpi_match_table = i2c_gpio_acpi_match, |
| }, |
| .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"); |