/* * Bitbanging I2C bus driver using the GPIO API * * Copyright (C) 2007 Atmel Corporation * * This program is free software; you can redistribute it and/or modify * it under the terms of the GNU General Public License version 2 as * published by the Free Software Foundation. */ #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 (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"); 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(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"); MODULE_ALIAS("platform:i2c-gpio");