i2c: core: add api to provide frequency mode strings

mainline inclusion
from mainline-v5.13-rc1
commit 3b4c747c
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I42E7E
CVE: NA

---------------------------

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.

Add the definition of the I2C Frequency Modes macro.
Tested-by: NJarkko Nikula <jarkko.nikula@linux.intel.com>
Reviewed-by: NJarkko Nikula <jarkko.nikula@linux.intel.com>
Reviewed-by: NAndy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: NYicong Yang <yangyicong@hisilicon.com>
Signed-off-by: NWolfram Sang <wsa@kernel.org>
Signed-off-by: Jiaran Zhang <zhangjiaran@huawei.com>
Reviewed-by: Sheng Feng < fengsheng5@huawei.com>
Signed-off-by: NYang Yingliang <yangyingliang@huawei.com>

drivers/i2c/i2c-core-base.c

@@ -84,6 +84,27 @@ void i2c_transfer_trace_unreg(void)
 	static_branch_dec(&i2c_trace_msg_key);
 }
 
+const char *i2c_freq_mode_string(u32 bus_freq_hz)
+{
+	switch (bus_freq_hz) {
+	case I2C_MAX_STANDARD_MODE_FREQ:
+		return "Standard Mode (100 kHz)";
+	case I2C_MAX_FAST_MODE_FREQ:
+		return "Fast Mode (400 kHz)";
+	case I2C_MAX_FAST_MODE_PLUS_FREQ:
+		return "Fast Mode Plus (1.0 MHz)";
+	case I2C_MAX_TURBO_MODE_FREQ:
+		return "Turbo Mode (1.4 MHz)";
+	case I2C_MAX_HIGH_SPEED_MODE_FREQ:
+		return "High Speed Mode (3.4 MHz)";
+	case I2C_MAX_ULTRA_FAST_MODE_FREQ:
+		return "Ultra Fast Mode (5.0 MHz)";
+	default:
+		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)
 {

include/linux/i2c.h

@@ -53,10 +53,21 @@ struct i2c_board_info;
 enum i2c_slave_event;
 typedef int (*i2c_slave_cb_t)(struct i2c_client *, enum i2c_slave_event, u8 *);
 
+/* 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;
 
 #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