i2c: stm32f7: fix configuration of the digital filter

The digital filter related computation are present in the driver
however the programming of the filter within the IP is missing.
The maximum value for the DNF is wrong and should be 15 instead of 16.

Fixes: aeb068c ("i2c: i2c-stm32f7: add driver")

Signed-off-by: Alain Volmat <alain.volmat@foss.st.com>
Signed-off-by: Pierre-Yves MORDRET <pierre-yves.mordret@foss.st.com>
Signed-off-by: Wolfram Sang <wsa@kernel.org>

Author: Alain Volmat

drivers/i2c/busses/i2c-stm32f7.c

@@ -57,6 +57,8 @@
 #define STM32F7_I2C_CR1_RXDMAEN			BIT(15)
 #define STM32F7_I2C_CR1_TXDMAEN			BIT(14)
 #define STM32F7_I2C_CR1_ANFOFF			BIT(12)
+#define STM32F7_I2C_CR1_DNF_MASK		GENMASK(11, 8)
+#define STM32F7_I2C_CR1_DNF(n)			(((n) & 0xf) << 8)
 #define STM32F7_I2C_CR1_ERRIE			BIT(7)
 #define STM32F7_I2C_CR1_TCIE			BIT(6)
 #define STM32F7_I2C_CR1_STOPIE			BIT(5)
@@ -160,7 +162,7 @@ enum {
 };
 
 #define STM32F7_I2C_DNF_DEFAULT			0
-#define STM32F7_I2C_DNF_MAX			16
+#define STM32F7_I2C_DNF_MAX			15
 
 #define STM32F7_I2C_ANALOG_FILTER_ENABLE	1
 #define STM32F7_I2C_ANALOG_FILTER_DELAY_MIN	50	/* ns */
@@ -725,6 +727,13 @@ static void stm32f7_i2c_hw_config(struct stm32f7_i2c_dev *i2c_dev)
 	else
 		stm32f7_i2c_set_bits(i2c_dev->base + STM32F7_I2C_CR1,
 				     STM32F7_I2C_CR1_ANFOFF);
+
+	/* Program the Digital Filter */
+	stm32f7_i2c_clr_bits(i2c_dev->base + STM32F7_I2C_CR1,
+			     STM32F7_I2C_CR1_DNF_MASK);
+	stm32f7_i2c_set_bits(i2c_dev->base + STM32F7_I2C_CR1,
+			     STM32F7_I2C_CR1_DNF(i2c_dev->setup.dnf));
+
 	stm32f7_i2c_set_bits(i2c_dev->base + STM32F7_I2C_CR1,
 			     STM32F7_I2C_CR1_PE);
 }