[PATCH] i2c: core: add api to provide frequency mode strings

[Yicong Yang]

Some I2C drivers like Designware and HiSilicon will print the
bus frequency mode information, so add a public one that everyone
can make use of.

Tested-by: Jarkko Nikula <jarkko.nikula@xxxxxxxxxxxxxxx>
Reviewed-by: Jarkko Nikula <jarkko.nikula@xxxxxxxxxxxxxxx>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx>
Signed-off-by: Yicong Yang <yangyicong@xxxxxxxxxxxxx>
---
 drivers/i2c/i2c-core-base.c | 19 +++++++++++++++++++
 include/linux/i2c.h         |  3 +++
 2 files changed, 22 insertions(+)

diff --git a/drivers/i2c/i2c-core-base.c b/drivers/i2c/i2c-core-base.c
index de9402c..53836b5 100644
--- a/drivers/i2c/i2c-core-base.c
+++ b/drivers/i2c/i2c-core-base.c
@@ -76,6 +76,25 @@ void i2c_transfer_trace_unreg(void)
 	static_branch_dec(&i2c_trace_msg_key);
 }

+const char *i2c_freq_mode_string(u32 bus_freq_hz)
+{
+	if (bus_freq_hz <= I2C_MAX_STANDARD_MODE_FREQ)
+		return "Standard Mode (max 100 kHz)";
+	else if (bus_freq_hz <= I2C_MAX_FAST_MODE_FREQ)
+		return "Fast Mode (max 400 kHz)";
+	else if (bus_freq_hz <= I2C_MAX_FAST_MODE_PLUS_FREQ)
+		return "Fast Mode Plus (max 1.0 MHz)";
+	else if (bus_freq_hz <= I2C_MAX_TURBO_MODE_FREQ)
+		return "Turbo Mode (max 1.4 MHz)";
+	else if (bus_freq_hz <= I2C_MAX_HIGH_SPEED_MODE_FREQ)
+		return "High Speed Mode (max 3.4 MHz)";
+	else if (bus_freq_hz <= I2C_MAX_ULTRA_FAST_MODE_FREQ)
+		return "Ultra Fast Mode (max 5.0 MHz)";
+	else
+		return "Unknown Mode";
+}
+EXPORT_SYMBOL_GPL(i2c_freq_mode_string);
+
 const struct i2c_device_id *i2c_match_id(const struct i2c_device_id *id,
 						const struct i2c_client *client)
 {
diff --git a/include/linux/i2c.h b/include/linux/i2c.h
index 10bd0b0..0813be1 100644
--- a/include/linux/i2c.h
+++ b/include/linux/i2c.h
@@ -51,6 +51,9 @@ struct module;
 struct property_entry;

 #if IS_ENABLED(CONFIG_I2C)
+/* Return the Frequency mode string based on the bus frequency */
+const char *i2c_freq_mode_string(u32 bus_freq_hz);
+
 /*
  * The master routines are the ones normally used to transmit data to devices
  * on a bus (or read from them). Apart from two basic transfer functions to
-- 
2.8.1