diff options
Diffstat (limited to 'drivers/i2c')
| -rw-r--r-- | drivers/i2c/i2c-core.c | 53 |
1 files changed, 53 insertions, 0 deletions
diff --git a/drivers/i2c/i2c-core.c b/drivers/i2c/i2c-core.c index ba8eb087f224..b34c412bd2c2 100644 --- a/drivers/i2c/i2c-core.c +++ b/drivers/i2c/i2c-core.c @@ -53,6 +53,7 @@ #include <linux/jump_label.h> #include <asm/uaccess.h> #include <linux/err.h> +#include <linux/property.h> #include "i2c-core.h" @@ -1438,6 +1439,58 @@ static void of_i2c_register_devices(struct i2c_adapter *adap) } } +/** + * i2c_parse_fw_timings - get I2C related timing parameters from firmware + * @dev: The device to scan for I2C timing properties + * @t: the i2c_timings struct to be filled with values + * @use_defaults: bool to use sane defaults derived from the I2C specification + * when properties are not found, otherwise use 0 + * + * Scan the device for the generic I2C properties describing timing parameters + * for the signal and fill the given struct with the results. If a property was + * not found and use_defaults was true, then maximum timings are assumed which + * are derived from the I2C specification. If use_defaults is not used, the + * results will be 0, so drivers can apply their own defaults later. The latter + * is mainly intended for avoiding regressions of existing drivers which want + * to switch to this function. New drivers almost always should use the defaults. + */ + +void i2c_parse_fw_timings(struct device *dev, struct i2c_timings *t, bool use_defaults) +{ + int ret; + + memset(t, 0, sizeof(*t)); + + ret = device_property_read_u32(dev, "clock-frequency", &t->bus_freq_hz); + if (ret && use_defaults) + t->bus_freq_hz = 100000; + + ret = device_property_read_u32(dev, "i2c-scl-rising-time-ns", &t->scl_rise_ns); + if (ret && use_defaults) { + if (t->bus_freq_hz <= 100000) + t->scl_rise_ns = 1000; + else if (t->bus_freq_hz <= 400000) + t->scl_rise_ns = 300; + else + t->scl_rise_ns = 120; + } + + ret = device_property_read_u32(dev, "i2c-scl-falling-time-ns", &t->scl_fall_ns); + if (ret && use_defaults) { + if (t->bus_freq_hz <= 400000) + t->scl_fall_ns = 300; + else + t->scl_fall_ns = 120; + } + + device_property_read_u32(dev, "i2c-scl-internal-delay-ns", &t->scl_int_delay_ns); + + ret = device_property_read_u32(dev, "i2c-sda-falling-time-ns", &t->sda_fall_ns); + if (ret && use_defaults) + t->sda_fall_ns = t->scl_fall_ns; +} +EXPORT_SYMBOL_GPL(i2c_parse_fw_timings); + static int of_dev_node_match(struct device *dev, void *data) { return dev->of_node == data; |