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Commit e1dba01c authored by Wolfram Sang's avatar Wolfram Sang Committed by Wolfram Sang
Browse files

i2c: add generic routine to parse DT for timing information 



Inspired from the i2c-rk3x driver (thanks guys!) but refactored and
extended. See built-in docs for further information.

Signed-off-by: default avatarWolfram Sang <wsa+renesas@sang-engineering.com>
Reviewed-by: default avatarMika Westerberg <mika.westerberg@linux.intel.com>
Signed-off-by: default avatarWolfram Sang <wsa@the-dreams.de>
parent 99b809d7

drivers/i2c/i2c-core.c

+53 −0
Original line number Diff line number Diff line
@@ -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;

include/linux/i2c.h

+18 −0
Original line number Diff line number Diff line
@@ -413,6 +413,22 @@ struct i2c_algorithm { 
#endif

};



/**

 * 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

 */

struct i2c_timings {

	u32 bus_freq_hz;

	u32 scl_rise_ns;

	u32 scl_fall_ns;

	u32 scl_int_delay_ns;

	u32 sda_fall_ns;

};



/**

 * struct i2c_bus_recovery_info - I2C bus recovery information

 * @recover_bus: Recover routine. Either pass driver's recover_bus() routine, or
@@ -604,6 +620,7 @@ extern void i2c_clients_command(struct i2c_adapter *adap, 
extern struct i2c_adapter *i2c_get_adapter(int nr);

extern void i2c_put_adapter(struct i2c_adapter *adap);



void i2c_parse_fw_timings(struct device *dev, struct i2c_timings *t, bool use_defaults);



/* Return the functionality mask */

static inline u32 i2c_get_functionality(struct i2c_adapter *adap)
@@ -660,6 +677,7 @@ extern struct i2c_adapter *of_find_i2c_adapter_by_node(struct device_node *node) 


/* must call i2c_put_adapter() when done with returned i2c_adapter device */

struct i2c_adapter *of_get_i2c_adapter_by_node(struct device_node *node);



#else



static inline struct i2c_client *of_find_i2c_device_by_node(struct device_node *node)