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author | Ahmad Fatoum <a.fatoum@pengutronix.de> | 2019-09-09 11:15:39 +0200 |
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committer | Sascha Hauer <s.hauer@pengutronix.de> | 2019-09-09 15:44:30 +0200 |
commit | f1bdb261ca5e2af8bdcacb4bd1a884865b280c7d (patch) | |
tree | 5fe6a940457bfc2497536bfa1d784517a759949c | |
parent | fe2a71d7f85a811c29586de99ced12ef89ad9e95 (diff) | |
download | barebox-f1bdb261ca5e2af8bdcacb4bd1a884865b280c7d.tar.gz barebox-f1bdb261ca5e2af8bdcacb4bd1a884865b280c7d.tar.xz |
i2c: port Linux i2c_parse_fw_timings
Linux has a generic function for extracting i2c timings parameters from
device-associated firmware nodes. Port this function to barebox, but
have it only work on device tree nodes for now.
Signed-off-by: Ahmad Fatoum <a.fatoum@pengutronix.de>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
-rw-r--r-- | drivers/i2c/i2c.c | 60 | ||||
-rw-r--r-- | include/i2c/i2c.h | 20 |
2 files changed, 80 insertions, 0 deletions
diff --git a/drivers/i2c/i2c.c b/drivers/i2c/i2c.c index 25e0fe7add..9df5ee70c7 100644 --- a/drivers/i2c/i2c.c +++ b/drivers/i2c/i2c.c @@ -557,6 +557,66 @@ struct i2c_adapter *of_find_i2c_adapter_by_node(struct device_node *node) } /** + * 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_d *dev, struct i2c_timings *t, bool use_defaults) +{ + int ret; + + memset(t, 0, sizeof(*t)); + + ret = of_property_read_u32(dev->device_node, "clock-frequency", + &t->bus_freq_hz); + if (ret && use_defaults) + t->bus_freq_hz = 100000; + + ret = of_property_read_u32(dev->device_node, "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 = of_property_read_u32(dev->device_node, "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; + } + + of_property_read_u32(dev->device_node, "i2c-scl-internal-delay-ns", + &t->scl_int_delay_ns); + + ret = of_property_read_u32(dev->device_node, "i2c-sda-falling-time-ns", + &t->sda_fall_ns); + if (ret && use_defaults) + t->sda_fall_ns = t->scl_fall_ns; + + of_property_read_u32(dev->device_node, "i2c-sda-hold-time-ns", + &t->sda_hold_ns); +} +EXPORT_SYMBOL_GPL(i2c_parse_fw_timings); + +/** * i2c_add_numbered_adapter - declare i2c adapter, use static bus number * @adapter: the adapter to register (with adap->nr initialized) * diff --git a/include/i2c/i2c.h b/include/i2c/i2c.h index 17b507ca22..a694e4ab2f 100644 --- a/include/i2c/i2c.h +++ b/include/i2c/i2c.h @@ -239,6 +239,24 @@ struct i2c_board_info { }; /** + * struct i2c_timings - I2C timing information + * @bus_freq_hz: the bus frequency in Hz + * @scl_rise_ns: time SCL signal takes to rise in ns; t(r) in the I2C specification + * @scl_fall_ns: time SCL signal takes to fall in ns; t(f) in the I2C specification + * @scl_int_delay_ns: time IP core additionally needs to setup SCL in ns + * @sda_fall_ns: time SDA signal takes to fall in ns; t(f) in the I2C specification + * @sda_hold_ns: time IP core additionally needs to hold SDA in ns + */ +struct i2c_timings { + u32 bus_freq_hz; + u32 scl_rise_ns; + u32 scl_fall_ns; + u32 scl_int_delay_ns; + u32 sda_fall_ns; + u32 sda_hold_ns; +}; + +/** * I2C_BOARD_INFO - macro used to list an i2c device and its address * @dev_type: identifies the device type * @dev_addr: the device's address on the bus. @@ -264,6 +282,8 @@ extern int i2c_add_numbered_adapter(struct i2c_adapter *adapter); struct i2c_adapter *i2c_get_adapter(int busnum); struct i2c_adapter *of_find_i2c_adapter_by_node(struct device_node *node); +void i2c_parse_fw_timings(struct device_d *dev, struct i2c_timings *t, bool use_defaults); + extern struct list_head i2c_adapter_list; #define for_each_i2c_adapter(adap) \ list_for_each_entry(adap, &i2c_adapter_list, list) |