diff --git a/components/driver/i2c.c b/components/driver/i2c.c
index de12e675d8..cdcf713058 100644
--- a/components/driver/i2c.c
+++ b/components/driver/i2c.c
@@ -189,10 +189,10 @@ static i2c_clk_alloc_t i2c_clk_alloc[I2C_SCLK_MAX] = {
     {0, I2C_CLK_LIMIT_XTAL},                                                               /*!< I2C XTAL characteristic*/
 #endif
 #if SOC_I2C_SUPPORT_RTC
-    {I2C_SCLK_SRC_FLAG_LIGHT_SLEEP, I2C_CLK_LIMIT_RTC},                                    /*!< I2C 20M RTC characteristic*/
+    {I2C_SCLK_SRC_FLAG_LIGHT_SLEEP | I2C_SCLK_SRC_FLAG_AWARE_DFS, I2C_CLK_LIMIT_RTC},      /*!< I2C 20M RTC characteristic*/
 #endif
 #if SOC_I2C_SUPPORT_REF_TICK
-    {I2C_SCLK_SRC_FLAG_AWARE_DFS | I2C_SCLK_SRC_FLAG_LIGHT_SLEEP, I2C_CLK_LIMIT_REF_TICK}, /*!< I2C REF_TICK characteristic*/
+    {I2C_SCLK_SRC_FLAG_AWARE_DFS, I2C_CLK_LIMIT_REF_TICK},                                 /*!< I2C REF_TICK characteristic*/
 #endif
 };
 
@@ -628,7 +628,7 @@ static i2c_sclk_t i2c_get_clk_src(const i2c_config_t *i2c_conf)
             continue;
         }
 #endif
-        if (((i2c_conf->clk_flags | i2c_clk_alloc[clk].character) == i2c_clk_alloc[clk].character) && (i2c_conf->master.clk_speed <= i2c_clk_alloc[clk].clk_freq)) {
+        if (((i2c_conf->clk_flags & i2c_clk_alloc[clk].character) == i2c_conf->clk_flags) && (i2c_conf->master.clk_speed <= i2c_clk_alloc[clk].clk_freq)) {
             return clk;
         }
     }
@@ -640,6 +640,9 @@ esp_err_t i2c_param_config(i2c_port_t i2c_num, const i2c_config_t *i2c_conf)
     I2C_CHECK(i2c_num < I2C_NUM_MAX, I2C_NUM_ERROR_STR, ESP_ERR_INVALID_ARG);
     I2C_CHECK(i2c_conf != NULL, I2C_ADDR_ERROR_STR, ESP_ERR_INVALID_ARG);
     I2C_CHECK(i2c_conf->mode < I2C_MODE_MAX, I2C_MODE_ERR_STR, ESP_ERR_INVALID_ARG);
+    if (i2c_conf->mode == I2C_MODE_MASTER) {
+        I2C_CHECK(i2c_get_clk_src(i2c_conf) != I2C_SCLK_MAX, I2C_CLK_FLAG_ERR_STR, ESP_ERR_INVALID_ARG);
+    }
 
     esp_err_t ret = i2c_set_pin(i2c_num, i2c_conf->sda_io_num, i2c_conf->scl_io_num,
                                 i2c_conf->sda_pullup_en, i2c_conf->scl_pullup_en, i2c_conf->mode);
@@ -664,7 +667,6 @@ esp_err_t i2c_param_config(i2c_port_t i2c_num, const i2c_config_t *i2c_conf)
         i2c_hal_master_init(&(i2c_context[i2c_num].hal), i2c_num);
         //Default, we enable hardware filter
         i2c_hal_set_filter(&(i2c_context[i2c_num].hal), I2C_FILTER_CYC_NUM_DEF);
-        I2C_CHECK(i2c_get_clk_src(i2c_conf) != I2C_SCLK_MAX, I2C_CLK_FLAG_ERR_STR, ESP_ERR_INVALID_ARG);
         i2c_hal_set_bus_timing(&(i2c_context[i2c_num].hal), i2c_conf->master.clk_speed, i2c_get_clk_src(i2c_conf));
     }
     I2C_EXIT_CRITICAL(&(i2c_context[i2c_num].spinlock));
diff --git a/examples/peripherals/i2c/i2c_self_test/main/i2c_example_main.c b/examples/peripherals/i2c/i2c_self_test/main/i2c_example_main.c
index ad70cbcba0..7b7928c1ad 100644
--- a/examples/peripherals/i2c/i2c_self_test/main/i2c_example_main.c
+++ b/examples/peripherals/i2c/i2c_self_test/main/i2c_example_main.c
@@ -144,14 +144,19 @@ static esp_err_t i2c_master_sensor_test(i2c_port_t i2c_num, uint8_t *data_h, uin
 static esp_err_t i2c_master_init(void)
 {
     int i2c_master_port = I2C_MASTER_NUM;
-    i2c_config_t conf;
-    conf.mode = I2C_MODE_MASTER;
-    conf.sda_io_num = I2C_MASTER_SDA_IO;
-    conf.sda_pullup_en = GPIO_PULLUP_ENABLE;
-    conf.scl_io_num = I2C_MASTER_SCL_IO;
-    conf.scl_pullup_en = GPIO_PULLUP_ENABLE;
-    conf.master.clk_speed = I2C_MASTER_FREQ_HZ;
-    i2c_param_config(i2c_master_port, &conf);
+    i2c_config_t conf = {
+        .mode = I2C_MODE_MASTER,
+        .sda_io_num = I2C_MASTER_SDA_IO,
+        .sda_pullup_en = GPIO_PULLUP_ENABLE,
+        .scl_io_num = I2C_MASTER_SCL_IO,
+        .scl_pullup_en = GPIO_PULLUP_ENABLE,
+        .master.clk_speed = I2C_MASTER_FREQ_HZ,
+        // .clk_flags = 0,          /*!< Optional, you can use I2C_SCLK_SRC_FLAG_* flags to choose i2c source clock here. */
+    };
+    esp_err_t err = i2c_param_config(i2c_master_port, &conf);
+    if (err != ESP_OK) {
+        return err;
+    }
     return i2c_driver_install(i2c_master_port, conf.mode, I2C_MASTER_RX_BUF_DISABLE, I2C_MASTER_TX_BUF_DISABLE, 0);
 }
 
@@ -161,15 +166,19 @@ static esp_err_t i2c_master_init(void)
 static esp_err_t i2c_slave_init(void)
 {
     int i2c_slave_port = I2C_SLAVE_NUM;
-    i2c_config_t conf_slave;
-    conf_slave.sda_io_num = I2C_SLAVE_SDA_IO;
-    conf_slave.sda_pullup_en = GPIO_PULLUP_ENABLE;
-    conf_slave.scl_io_num = I2C_SLAVE_SCL_IO;
-    conf_slave.scl_pullup_en = GPIO_PULLUP_ENABLE;
-    conf_slave.mode = I2C_MODE_SLAVE;
-    conf_slave.slave.addr_10bit_en = 0;
-    conf_slave.slave.slave_addr = ESP_SLAVE_ADDR;
-    i2c_param_config(i2c_slave_port, &conf_slave);
+    i2c_config_t conf_slave = {
+        .sda_io_num = I2C_SLAVE_SDA_IO,
+        .sda_pullup_en = GPIO_PULLUP_ENABLE,
+        .scl_io_num = I2C_SLAVE_SCL_IO,
+        .scl_pullup_en = GPIO_PULLUP_ENABLE,
+        .mode = I2C_MODE_SLAVE,
+        .slave.addr_10bit_en = 0,
+        .slave.slave_addr = ESP_SLAVE_ADDR,
+    };
+    esp_err_t err = i2c_param_config(i2c_slave_port, &conf_slave);
+    if (err != ESP_OK) {
+        return err;
+    }
     return i2c_driver_install(i2c_slave_port, conf_slave.mode, I2C_SLAVE_RX_BUF_LEN, I2C_SLAVE_TX_BUF_LEN, 0);
 }
 
diff --git a/examples/peripherals/i2c/i2c_tools/main/cmd_i2ctools.c b/examples/peripherals/i2c/i2c_tools/main/cmd_i2ctools.c
index 4adb0b9ea2..5a2138a692 100644
--- a/examples/peripherals/i2c/i2c_tools/main/cmd_i2ctools.c
+++ b/examples/peripherals/i2c/i2c_tools/main/cmd_i2ctools.c
@@ -56,7 +56,8 @@ static esp_err_t i2c_master_driver_initialize(void)
         .sda_pullup_en = GPIO_PULLUP_ENABLE,
         .scl_io_num = i2c_gpio_scl,
         .scl_pullup_en = GPIO_PULLUP_ENABLE,
-        .master.clk_speed = i2c_frequency
+        .master.clk_speed = i2c_frequency,
+        // .clk_flags = 0,          /*!< Optional, you can use I2C_SCLK_SRC_FLAG_* flags to choose i2c source clock here. */
     };
     return i2c_param_config(i2c_port, &conf);
 }