[PATCH v3 5/7] can: dev: add a helper function to calculate the duration of one bit
From: Vincent Mailhol <hidden>
Date: 2020-10-02 15:51:51
Also in:
linux-can, linux-usb, lkml
Subsystem:
can network drivers, the rest · Maintainers:
Marc Kleine-Budde, Vincent Mailhol, Linus Torvalds
Rename macro CAN_CALC_SYNC_SEG to CAN_SYNC_SEG and make it available through include/linux/can/dev.h Add an helper function can_bit_time() which returns the duration (in time quanta) of one CAN bit. Rationale for this patch: the sync segment and the bit time are two concepts which are defined in the CAN ISO standard. Device drivers for CAN might need those. Please refer to ISO 11898-1:2015, section 11.3.1.1 "Bit time" for additional information. Signed-off-by: Vincent Mailhol <redacted> --- Changes in v3: None Changes in v2: None --- drivers/net/can/dev.c | 13 ++++++------- include/linux/can/dev.h | 15 +++++++++++++++ 2 files changed, 21 insertions(+), 7 deletions(-)
diff --git a/drivers/net/can/dev.c b/drivers/net/can/dev.c
index 8c3e11820e03..6070b4ab3bd8 100644
--- a/drivers/net/can/dev.c
+++ b/drivers/net/can/dev.c@@ -60,7 +60,6 @@ EXPORT_SYMBOL_GPL(can_len2dlc); #ifdef CONFIG_CAN_CALC_BITTIMING #define CAN_CALC_MAX_ERROR 50 /* in one-tenth of a percent */ -#define CAN_CALC_SYNC_SEG 1 /* Bit-timing calculation derived from: *
@@ -86,8 +85,8 @@ can_update_sample_point(const struct can_bittiming_const *btc, int i; for (i = 0; i <= 1; i++) { - tseg2 = tseg + CAN_CALC_SYNC_SEG - - (sample_point_nominal * (tseg + CAN_CALC_SYNC_SEG)) / + tseg2 = tseg + CAN_SYNC_SEG - + (sample_point_nominal * (tseg + CAN_SYNC_SEG)) / 1000 - i; tseg2 = clamp(tseg2, btc->tseg2_min, btc->tseg2_max); tseg1 = tseg - tseg2;
@@ -96,8 +95,8 @@ can_update_sample_point(const struct can_bittiming_const *btc, tseg2 = tseg - tseg1; } - sample_point = 1000 * (tseg + CAN_CALC_SYNC_SEG - tseg2) / - (tseg + CAN_CALC_SYNC_SEG); + sample_point = 1000 * (tseg + CAN_SYNC_SEG - tseg2) / + (tseg + CAN_SYNC_SEG); sample_point_error = abs(sample_point_nominal - sample_point); if (sample_point <= sample_point_nominal &&
@@ -145,7 +144,7 @@ static int can_calc_bittiming(struct net_device *dev, struct can_bittiming *bt, /* tseg even = round down, odd = round up */ for (tseg = (btc->tseg1_max + btc->tseg2_max) * 2 + 1; tseg >= (btc->tseg1_min + btc->tseg2_min) * 2; tseg--) { - tsegall = CAN_CALC_SYNC_SEG + tseg / 2; + tsegall = CAN_SYNC_SEG + tseg / 2; /* Compute all possible tseg choices (tseg=tseg1+tseg2) */ brp = priv->clock.freq / (tsegall * bt->bitrate) + tseg % 2;
@@ -223,7 +222,7 @@ static int can_calc_bittiming(struct net_device *dev, struct can_bittiming *bt, /* real bitrate */ bt->bitrate = priv->clock.freq / - (bt->brp * (CAN_CALC_SYNC_SEG + tseg1 + tseg2)); + (bt->brp * (CAN_SYNC_SEG + tseg1 + tseg2)); return 0; }
diff --git a/include/linux/can/dev.h b/include/linux/can/dev.h
index 791c452d98e1..77c3ea49b8fb 100644
--- a/include/linux/can/dev.h
+++ b/include/linux/can/dev.h@@ -82,6 +82,21 @@ struct can_priv { #endif }; +#define CAN_SYNC_SEG 1 + +/* + * can_bit_time() - Duration of one bit + * + * Please refer to ISO 11898-1:2015, section 11.3.1.1 "Bit time" for + * additional information. + * + * Return: the number of time quanta in one bit. + */ +static inline int can_bit_time(struct can_bittiming *bt) +{ + return CAN_SYNC_SEG + bt->prop_seg + bt->phase_seg1 + bt->phase_seg2; +} + /* * get_can_dlc(value) - helper macro to cast a given data length code (dlc) * to u8 and ensure the dlc value to be max. 8 bytes.
--
2.26.2