On 16.08.2021 14:25:19, Marc Kleine-Budde wrote: > > > I'm not sure, if we talked about the mcp251xfd's tcdo, valid values are > > > -64...63. > > > > Yes! Stefan shed some light on this. The mcp251xfd uses a tdco > > value which is relative to the sample point. > > I don't read the documentation this way.... > > > | SSP = TDCV + absolute TDCO > > | = TDCV + SP + relative TDCO > > > > Consequently: > > | relative TDCO = absolute TDCO - SP > > In the mcp15xxfd family manual > (http://ww1.microchip.com/downloads/en/DeviceDoc/MCP251XXFD-CAN-FD-Controller-Module-Family-Reference-Manual-20005678B.pdf) > in the 2mbit/s data bit rate example in table 3-5 (page 21) it says: > > | DTSEG1 15 DTQ > | DTSEG2 4 DTQ > | TDCO 15 DTQ > > The mcp251xfd driver uses 15, the framework calculates 16 (== Sync Seg+ > tseg1, which is correct), and relative tdco would be 0: > > | mcp251xfd_set_bittiming: tdco=15, priv->tdc.tdc=16, relative_tdco=0 > > Here the output with the patched ip tool: Sorry, the previous output was not using the sample points of the example in the data sheet, this is the fixed output: | 6: mcp251xfd0: mtu 72 qdisc pfifo_fast state UP mode DEFAULT group default qlen 10 | link/can promiscuity 0 minmtu 0 maxmtu 0 | can state ERROR-ACTIVE (berr-counter tx 0 rx 0) restart-ms 100 | bitrate 500000 sample-point 0.800 | tq 25 prop-seg 31 phase-seg1 32 phase-seg2 16 sjw 1 brp 1 | mcp251xfd: tseg1 2..256 tseg2 1..128 sjw 1..128 brp 1..256 brp_inc 1 | dbitrate 2000000 dsample-point 0.800 | dtq 25 dprop-seg 7 dphase-seg1 8 dphase-seg2 4 dsjw 1 dbrp 1 | tdco 16 | mcp251xfd: dtseg1 1..32 dtseg2 1..16 dsjw 1..16 dbrp 1..256 dbrp_inc 1 | tdco 0..127 | clock 40000000 numtxqueues 1 numrxqueues 1 gso_max_size 65536 gso_max_segs 65535 parentbus spi parentdev spi0.0 Marc -- Pengutronix e.K. | Marc Kleine-Budde | Embedded Linux | https://www.pengutronix.de | Vertretung West/Dortmund | Phone: +49-231-2826-924 | Amtsgericht Hildesheim, HRA 2686 | Fax: +49-5121-206917-5555 |