diff options
Diffstat (limited to 'drivers/i2c/busses/i2c-gpio.c')
| -rw-r--r-- | drivers/i2c/busses/i2c-gpio.c | 290 |
1 files changed, 290 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..34cfc0ebd --- /dev/null +++ b/drivers/i2c/busses/i2c-gpio.c @@ -0,0 +1,290 @@ +/* + * 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/i2c.h> +#include <linux/i2c-algo-bit.h> +#include <linux/i2c-gpio.h> +#include <linux/init.h> +#include <linux/module.h> +#include <linux/slab.h> +#include <linux/platform_device.h> +#include <linux/gpio.h> +#include <linux/of.h> +#include <linux/of_gpio.h> + +struct i2c_gpio_private_data { + struct i2c_adapter adap; + struct i2c_algo_bit_data bit_data; + struct i2c_gpio_platform_data pdata; +}; + +/* Toggle SDA by changing the direction of the pin */ +static void i2c_gpio_setsda_dir(void *data, int state) +{ + struct i2c_gpio_platform_data *pdata = data; + + if (state) + gpio_direction_input(pdata->sda_pin); + else + gpio_direction_output(pdata->sda_pin, 0); +} + +/* + * 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_platform_data *pdata = data; + + gpio_set_value(pdata->sda_pin, state); +} + +/* Toggle SCL by changing the direction of the pin. */ +static void i2c_gpio_setscl_dir(void *data, int state) +{ + struct i2c_gpio_platform_data *pdata = data; + + if (state) + gpio_direction_input(pdata->scl_pin); + else + gpio_direction_output(pdata->scl_pin, 0); +} + +/* + * 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_platform_data *pdata = data; + + gpio_set_value(pdata->scl_pin, state); +} + +static int i2c_gpio_getsda(void *data) +{ + struct i2c_gpio_platform_data *pdata = data; + + return gpio_get_value(pdata->sda_pin); +} + +static int i2c_gpio_getscl(void *data) +{ + struct i2c_gpio_platform_data *pdata = data; + + return gpio_get_value(pdata->scl_pin); +} + +static int of_i2c_gpio_get_pins(struct device_node *np, + unsigned int *sda_pin, unsigned int *scl_pin) +{ + if (of_gpio_count(np) < 2) + return -ENODEV; + + *sda_pin = of_get_gpio(np, 0); + *scl_pin = of_get_gpio(np, 1); + + if (*sda_pin == -EPROBE_DEFER || *scl_pin == -EPROBE_DEFER) + return -EPROBE_DEFER; + + if (!gpio_is_valid(*sda_pin) || !gpio_is_valid(*scl_pin)) { + pr_err("%s: invalid GPIO pins, sda=%d/scl=%d\n", + np->full_name, *sda_pin, *scl_pin); + return -ENODEV; + } + + return 0; +} + +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 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; + unsigned int sda_pin, scl_pin; + int ret; + + /* First get the GPIO pins; if it fails, we'll defer the probe. */ + if (pdev->dev.of_node) { + ret = of_i2c_gpio_get_pins(pdev->dev.of_node, + &sda_pin, &scl_pin); + if (ret) + return ret; + } else { + if (!dev_get_platdata(&pdev->dev)) + return -ENXIO; + pdata = dev_get_platdata(&pdev->dev); + sda_pin = pdata->sda_pin; + scl_pin = pdata->scl_pin; + } + + ret = devm_gpio_request(&pdev->dev, sda_pin, "sda"); + if (ret) { + if (ret == -EINVAL) + ret = -EPROBE_DEFER; /* Try again later */ + return ret; + } + ret = devm_gpio_request(&pdev->dev, scl_pin, "scl"); + if (ret) { + if (ret == -EINVAL) + ret = -EPROBE_DEFER; /* Try again later */ + return ret; + } + + priv = devm_kzalloc(&pdev->dev, sizeof(*priv), GFP_KERNEL); + if (!priv) + return -ENOMEM; + adap = &priv->adap; + bit_data = &priv->bit_data; + pdata = &priv->pdata; + + if (pdev->dev.of_node) { + pdata->sda_pin = sda_pin; + pdata->scl_pin = scl_pin; + of_i2c_gpio_get_props(pdev->dev.of_node, pdata); + } else { + memcpy(pdata, dev_get_platdata(&pdev->dev), sizeof(*pdata)); + } + + if (pdata->sda_is_open_drain) { + gpio_direction_output(pdata->sda_pin, 1); + bit_data->setsda = i2c_gpio_setsda_val; + } else { + gpio_direction_input(pdata->sda_pin); + bit_data->setsda = i2c_gpio_setsda_dir; + } + + if (pdata->scl_is_open_drain || pdata->scl_is_output_only) { + gpio_direction_output(pdata->scl_pin, 1); + bit_data->setscl = i2c_gpio_setscl_val; + } else { + gpio_direction_input(pdata->scl_pin); + bit_data->setscl = i2c_gpio_setscl_dir; + } + + 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 = pdata; + + adap->owner = THIS_MODULE; + if (pdev->dev.of_node) + strlcpy(adap->name, dev_name(&pdev->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 = &pdev->dev; + adap->dev.of_node = pdev->dev.of_node; + + adap->nr = pdev->id; + ret = i2c_bit_add_numbered_bus(adap); + if (ret) + return ret; + + platform_set_drvdata(pdev, priv); + + dev_info(&pdev->dev, "using pins %u (SDA) and %u (SCL%s)\n", + pdata->sda_pin, pdata->scl_pin, + pdata->scl_is_output_only + ? ", no clock stretching" : ""); + + return 0; +} + +static int i2c_gpio_remove(struct platform_device *pdev) +{ + struct i2c_gpio_private_data *priv; + struct i2c_adapter *adap; + + 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"); |