drivers: can: change sample point for can_set_bitrate() at high bitrates (fba27b4b) · Commits · Wenxi XU / zephyr

drivers/can/can_common.c

+40 −2

Original line number	Diff line number	Diff line
		@@ -11,6 +11,9 @@

		LOG_MODULE_REGISTER(can_common, CONFIG_CAN_LOG_LEVEL);

		/* Maximum acceptable deviation in sample point location (permille) */
		#define SAMPLE_POINT_MARGIN 50

		/* CAN sync segment is always one time quantum */
		#define CAN_SYNC_SEG 1

		@@ -180,6 +183,30 @@ int can_calc_prescaler(const struct device dev, struct can_timing timing,
		return core_clock % (ts * timing->prescaler);
		}

		/**
		* @brief Get the sample point location for a given bitrate
		*
		* @param bitrate The bitrate in bits/second.
		* @return The sample point in permille.
		*/
		uint16_t sample_point_for_bitrate(uint32_t bitrate)
		{
		uint16_t sample_pnt;

		if (bitrate > 800000) {
		/* 75.0% */
		sample_pnt = 750;
		} else if (bitrate > 500000) {
		/* 80.0% */
		sample_pnt = 800;
		} else {
		/* 87.5% */
		sample_pnt = 875;
		}

		return sample_pnt;
		}

		int can_set_bitrate(const struct device *dev, uint32_t bitrate, uint32_t bitrate_data)
		{
		struct can_timing timing;
		@@ -187,6 +214,7 @@ int can_set_bitrate(const struct device *dev, uint32_t bitrate, uint32_t bitrate
		struct can_timing timing_data;
		#endif /* CONFIG_CAN_FD_MODE */
		uint32_t max_bitrate;
		uint16_t sample_pnt;
		int ret;

		ret = can_get_max_bitrate(dev, &max_bitrate);
		@@ -201,11 +229,16 @@ int can_set_bitrate(const struct device *dev, uint32_t bitrate, uint32_t bitrate
		return -ENOTSUP;
		}

		ret = can_calc_timing(dev, &timing, bitrate, 875);
		sample_pnt = sample_point_for_bitrate(bitrate);
		ret = can_calc_timing(dev, &timing, bitrate, sample_pnt);
		if (ret < 0) {
		return -EINVAL;
		}

		if (ret > SAMPLE_POINT_MARGIN) {
		return -EINVAL;
		}

		timing.sjw = CAN_SJW_NO_CHANGE;

		#ifdef CONFIG_CAN_FD_MODE
		@@ -213,11 +246,16 @@ int can_set_bitrate(const struct device *dev, uint32_t bitrate, uint32_t bitrate
		return -ENOTSUP;
		}

		ret = can_calc_timing_data(dev, &timing_data, bitrate_data, 875);
		sample_pnt = sample_point_for_bitrate(bitrate_data);
		ret = can_calc_timing_data(dev, &timing_data, bitrate_data, sample_pnt);
		if (ret < 0) {
		return -EINVAL;
		}

		if (ret > SAMPLE_POINT_MARGIN) {
		return -EINVAL;
		}

		timing_data.sjw = CAN_SJW_NO_CHANGE;

		return can_set_timing(dev, &timing, &timing_data);

include/zephyr/drivers/can.h

+9 −2

Original line number	Diff line number	Diff line
		@@ -845,7 +845,14 @@ static inline int z_impl_can_set_mode(const struct device *dev, enum can_mode mo
		/**
		* @brief Set the bitrate of the CAN controller
		*
		* The sample point is set to the CiA DS 301 recommended value of 87.5%.
		* CAN in Automation (CiA) 301 v4.2.0 recommends a sample point location of
		* 87.5% percent for all bitrates. However, some CAN controllers have
		* difficulties meeting this for higher bitrates.
		*
		* This function defaults to using a sample point of 75.0% for bitrates over 800
		* kbit/s, 80.0% for bitrates over 500 kbit/s, and 87.5% for all other
		* bitrates. This is in line with the sample point locations used by the Linux
		* kernel.
		*
		* @note The parameter ``bitrate_data`` is only relevant for CAN-FD. If the
		* controller does not support CAN-FD or if @kconfig{CONFIG_CAN_FD_MODE} is not
		@@ -857,7 +864,7 @@ static inline int z_impl_can_set_mode(const struct device *dev, enum can_mode mo
		*
		* @retval 0 If successful.
		* @retval -ENOTSUP bitrate not supported by CAN controller/transceiver combination
		* @retval -EINVAL bitrate cannot be met.
		* @retval -EINVAL bitrate/sample point cannot be met.
		* @retval -EIO General input/output error, failed to set bitrate.
		*/
		int can_set_bitrate(const struct device *dev, uint32_t bitrate, uint32_t bitrate_data);

Admin message