[PATCH net-next 13/27] can: calc_bittiming: add can_calc_sample_point_nrz()
From: Marc Kleine-Budde <mkl@pengutronix.de>
Date: 2025-11-26 12:01:33
Also in:
linux-can
Subsystem:
can network drivers, the rest · Maintainers:
Marc Kleine-Budde, Vincent Mailhol, Linus Torvalds
From: Vincent Mailhol <mailhol@kernel.org> CAN XL optimal sample point for PWM encoding (when TMS is on) differs from the NRZ optimal one. There is thus a need to calculate a different sample point depending whether TMS is on or off. This is a preparation change: move the sample point calculation from can_calc_bittiming() into the new can_calc_sample_point_nrz() function. In an upcoming change, a function will be added to calculate the sample point for PWM encoding. Signed-off-by: Vincent Mailhol <mailhol@kernel.org> Signed-off-by: Oliver Hartkopp <socketcan@hartkopp.net> Link: https://patch.msgid.link/20251126-canxl-v8-13-e7e3eb74f889@pengutronix.de Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de> --- drivers/net/can/dev/calc_bittiming.c | 25 +++++++++++++++---------- 1 file changed, 15 insertions(+), 10 deletions(-)
diff --git a/drivers/net/can/dev/calc_bittiming.c b/drivers/net/can/dev/calc_bittiming.c
index c8c166b383cd..bacdf3b218d3 100644
--- a/drivers/net/can/dev/calc_bittiming.c
+++ b/drivers/net/can/dev/calc_bittiming.c@@ -10,6 +10,18 @@ #define CAN_CALC_MAX_ERROR 50 /* in one-tenth of a percent */ +/* CiA recommended sample points for Non Return to Zero encoding. */ +static int can_calc_sample_point_nrz(const struct can_bittiming *bt) +{ + if (bt->bitrate > 800 * KILO /* BPS */) + return 750; + + if (bt->bitrate > 500 * KILO /* BPS */) + return 800; + + return 875; +} + /* Bit-timing calculation derived from: * * Code based on LinCAN sources and H8S2638 project
@@ -79,17 +91,10 @@ int can_calc_bittiming(const struct net_device *dev, struct can_bittiming *bt, u64 v64; int err; - /* Use CiA recommended sample points */ - if (bt->sample_point) { + if (bt->sample_point) sample_point_reference = bt->sample_point; - } else { - if (bt->bitrate > 800 * KILO /* BPS */) - sample_point_reference = 750; - else if (bt->bitrate > 500 * KILO /* BPS */) - sample_point_reference = 800; - else - sample_point_reference = 875; - } + else + sample_point_reference = can_calc_sample_point_nrz(bt); /* tseg even = round down, odd = round up */ for (tseg = (btc->tseg1_max + btc->tseg2_max) * 2 + 1;
--
2.51.0