[nrf fromlist] drivers: i2c: i2c_nrfx_twim: take clock tolerance into account

In calculation of the FREQUENCY register value take into account
the tolerance of the peripheral clock to ensure that the SCL
frequency does not exceed the specified value.

Upstream PR #: 104882

Signed-off-by: Michał Bainczyk <michal.bainczyk@nordicsemi.no>

Author: mib1-nordic

drivers/i2c/i2c_nrfx_twim_common.h

@@ -17,7 +17,25 @@ extern "C" {
 #endif
 
 #define I2C_NRFX_TWIM_INVALID_FREQUENCY ((nrf_twim_frequency_t)-1)
-#define I2C_NRFX_TWIM_FREQUENCY(bitrate)                                                           \
+
+/* Formula for getting the frequency settings is following:
+ * 2^12 * (2^20 / (f_PCLK / desired_frequency)) where f_PCLK is a frequency that
+ * drives the TWIM.
+ *
+ * @param f_pclk Frequency of the clock that drives the peripheral.
+ * @param baudrate Desired baudrate.
+ *
+ * @return Frequency setting to be written to the FREQUENCY register
+ */
+#define I2C_NRFX_TWIM_FREQUENCY_CALCULATE(bitrate, f_pclk) \
+	((nrf_twim_frequency_t)((BIT(20) / DIV_ROUND_CLOSEST(f_pclk, bitrate)) << 12))
+
+#define I2C_NRFX_TWIM_FREQUENCY_CALCULATE_CORRECTED(bitrate, f_pclk, tolerance_percent)		\
+	I2C_NRFX_TWIM_FREQUENCY_CALCULATE(bitrate,						\
+					  DIV_ROUND_CLOSEST(f_pclk * (100 + tolerance_percent), \
+					  100))
+
+#define I2C_NRFX_TWIM_FREQUENCY_ENUM_GET(bitrate, f_pclk)                                          \
 	(bitrate == I2C_BITRATE_STANDARD ? NRF_TWIM_FREQ_100K                                      \
 	 : bitrate == 250000             ? NRF_TWIM_FREQ_250K                                      \
 	 : bitrate == I2C_BITRATE_FAST                                                             \
@@ -26,8 +44,16 @@ extern "C" {
 			      (bitrate == I2C_BITRATE_FAST_PLUS ? NRF_TWIM_FREQ_1000K :))          \
 			   I2C_NRFX_TWIM_INVALID_FREQUENCY)
 
-#define I2C_FREQUENCY(inst) \
-	I2C_NRFX_TWIM_FREQUENCY(DT_INST_PROP_OR(inst, clock_frequency, I2C_BITRATE_STANDARD))
+#define INTENDED_CLOCK_FREQUENCY(inst) DT_INST_PROP_OR(inst, clock_frequency, I2C_BITRATE_STANDARD)
+#define CLOCK_TOLERANCE(inst) DT_INST_PROP(inst, clock_tolerance_percent)
+
+#define I2C_FREQUENCY(inst)									 \
+	COND_CODE_1(DT_INST_NODE_HAS_PROP(inst, clock_tolerance_percent),			 \
+		    (I2C_NRFX_TWIM_FREQUENCY_CALCULATE_CORRECTED(INTENDED_CLOCK_FREQUENCY(inst), \
+								 NRF_PERIPH_GET_FREQUENCY(inst), \
+								 CLOCK_TOLERANCE(inst))),	 \
+		    (I2C_NRFX_TWIM_FREQUENCY_ENUM_GET(INTENDED_CLOCK_FREQUENCY(inst),		 \
+						      NRF_PERIPH_GET_FREQUENCY(inst))))
 
 /* Macro determines PM actions interrupt safety level.
  *