From: Ondrej Ille ondrej.ille@gmail.com

The Secondary Sample Point Source field has been set to an incorrect value by some mistake in the past

0b01 - SSP_SRC_NO_SSP - SSP is not used.

for data bitrates above 1 MBit/s. The correct/default value already used for lower bitrates is

0b00 - SSP_SRC_MEAS_N_OFFSET - SSP position = TRV_DELAY (Measured Transmitter delay) + SSP_OFFSET.

The related configuration register structure is described in section 3.1.46 SSP_CFG of the CTU CAN FD IP CORE Datasheet.

The analysis leading to the proper configuration is described in section 2.8.3 Secondary sampling point of the datasheet.

The change has been tested on AMD/Xilinx Zynq with the next CTU CN FD IP core versions:

- 2.6 aka master in the "integration with Zynq-7000 system" test 6.12.43-rt12+ #1 SMP PREEMPT_RT kernel with CTU CAN FD git driver (change already included in the driver repo) - older 2.5 snapshot with mainline kernels with this patch applied locally in the multiple CAN latency tester nightly runs 6.18.0-rc4-rt3-dut #1 SMP PREEMPT_RT 6.19.0-rc3-dut

The logs, the datasheet and sources are available at

https://canbus.pages.fel.cvut.cz/

Signed-off-by: Ondrej Ille ondrej.ille@gmail.com Signed-off-by: Pavel Pisa pisa@fel.cvut.cz Link: https://patch.msgid.link/20260105111620.16580-1-pisa@fel.cvut.cz Fixes: 2dcb8e8782d8 ("can: ctucanfd: add support for CTU CAN FD open-source IP core - bus independent part.") Cc: stable@vger.kernel.org Signed-off-by: Marc Kleine-Budde mkl@pengutronix.de --- drivers/net/can/ctucanfd/ctucanfd_base.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/can/ctucanfd/ctucanfd_base.c b/drivers/net/can/ctucanfd/ctucanfd_base.c index 1e6b9e3dc2fe..0ea1ff28dfce 100644 --- a/drivers/net/can/ctucanfd/ctucanfd_base.c +++ b/drivers/net/can/ctucanfd/ctucanfd_base.c @@ -310,7 +310,7 @@ static int ctucan_set_secondary_sample_point(struct net_device *ndev) }

ssp_cfg = FIELD_PREP(REG_TRV_DELAY_SSP_OFFSET, ssp_offset); - ssp_cfg |= FIELD_PREP(REG_TRV_DELAY_SSP_SRC, 0x1); + ssp_cfg |= FIELD_PREP(REG_TRV_DELAY_SSP_SRC, 0x0); }

ctucan_write32(priv, CTUCANFD_TRV_DELAY, ssp_cfg);