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can: calc_bittiming: add can_calc_sample_point_nrz()

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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>
This commit is contained in:
Vincent Mailhol
2025-11-26 11:16:14 +01:00
committed by Marc Kleine-Budde
parent 1d147cb7c5
commit a6ddf91a4f
1 changed files with 15 additions and 10 deletions
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25
drivers/net/can/dev/calc_bittiming.c
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@@ -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;