i2c: core: Provide generic definitions for bus frequencies

There are few maximum bus frequencies being used in the I²C core code.
Provide generic definitions for bus frequencies and use them in the core.

The drivers may use predefined constants where it is appropriate.
Some of them are already using these under slightly different names.
We will convert them later to use newly introduced defines.

Note, the name of modes are chosen to follow well established naming
scheme [1].

These definitions will also help to avoid typos in the numbers that
may lead to subtle errors.

[1]: https://en.wikipedia.org/wiki/I%C2%B2C#Differences_between_modesAcked-by: NMika Westerberg <mika.westerberg@linux.intel.com>
Signed-off-by: NAndy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: NWolfram Sang <wsa@the-dreams.de>

drivers/i2c/i2c-core-acpi.c

@@ -318,7 +318,7 @@ static acpi_status i2c_acpi_lookup_speed(acpi_handle handle, u32 level,
 		lookup->min_speed = lookup->speed;
 
 	if (acpi_match_device_ids(adev, i2c_acpi_force_400khz_device_ids) == 0)
-		lookup->force_speed = 400000;
+		lookup->force_speed = I2C_MAX_FAST_MODE_FREQ;
 
 	return AE_OK;
 }

drivers/i2c/i2c-core-base.c

@@ -1612,13 +1612,13 @@ void i2c_parse_fw_timings(struct device *dev, struct i2c_timings *t, bool use_de
 
 	ret = device_property_read_u32(dev, "clock-frequency", &t->bus_freq_hz);
 	if (ret && use_defaults)
-		t->bus_freq_hz = 100000;
+		t->bus_freq_hz = I2C_MAX_STANDARD_MODE_FREQ;
 
 	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)
+		if (t->bus_freq_hz <= I2C_MAX_STANDARD_MODE_FREQ)
 			t->scl_rise_ns = 1000;
-		else if (t->bus_freq_hz <= 400000)
+		else if (t->bus_freq_hz <= I2C_MAX_FAST_MODE_FREQ)
 			t->scl_rise_ns = 300;
 		else
 			t->scl_rise_ns = 120;
@@ -1626,7 +1626,7 @@ void i2c_parse_fw_timings(struct device *dev, struct i2c_timings *t, bool use_de
 
 	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)
+		if (t->bus_freq_hz <= I2C_MAX_FAST_MODE_FREQ)
 			t->scl_fall_ns = 300;
 		else
 			t->scl_fall_ns = 120;

include/linux/i2c.h

@@ -39,6 +39,14 @@ enum i2c_slave_event;
 typedef int (*i2c_slave_cb_t)(struct i2c_client *client,
 			      enum i2c_slave_event event, u8 *val);
 
+/* I2C Frequency Modes */
+#define I2C_MAX_STANDARD_MODE_FREQ	100000
+#define I2C_MAX_FAST_MODE_FREQ		400000
+#define I2C_MAX_FAST_MODE_PLUS_FREQ	1000000
+#define I2C_MAX_TURBO_MODE_FREQ		1400000
+#define I2C_MAX_HIGH_SPEED_MODE_FREQ	3400000
+#define I2C_MAX_ULTRA_FAST_MODE_FREQ	5000000
+
 struct module;
 struct property_entry;