On 16.08.2021 14:33:09, Marc Kleine-Budde wrote: > 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 The following sequence doesn't clear "tdcv" properly: | ip link set dev mcp251xfd0 down; \ | ip link set mcp251xfd0 txqueuelen 10 up type can \ | sample-point 0.8 bitrate 500000 \ | dsample-point 0.8 dbitrate 2000000 fd on \ | tdc-mode manual tdco 11 tdcv 22 | | ip link set dev mcp251xfd0 down; \ | ip link set mcp251xfd0 txqueuelen 10 up type can \ | sample-point 0.8 bitrate 500000 \ | dsample-point 0.8 dbitrate 2000000 fd on | Aug 16 15:10:43 rpi4b8 kernel: mcp251xfd spi0.0 mcp251xfd0: mcp251xfd_set_bittiming: tdco=11 tdcv=22 mode=manual | Aug 16 15:10:43 rpi4b8 kernel: IPv6: ADDRCONF(NETDEV_CHANGE): mcp251xfd0: link becomes ready | Aug 16 15:10:59 rpi4b8 kernel: mcp251xfd spi0.0 mcp251xfd0: mcp251xfd_set_bittiming: tdco=16 tdcv=22 mode=automatic | Aug 16 15:10:59 rpi4b8 kernel: IPv6: ADDRCONF(NETDEV_CHANGE): mcp251xfd0: link becomes ready neither does "tdc-mode off": | Aug 16 15:12:18 rpi4b8 kernel: mcp251xfd spi0.0 mcp251xfd0: mcp251xfd_set_bittiming: tdco=11 tdcv=22 mode=off | Aug 16 15:12:18 rpi4b8 kernel: IPv6: ADDRCONF(NETDEV_CHANGE): mcp251xfd0: link becomes ready --- We have 4 operations: - tdc-mode off switch off tdc altogether - tdc-mode manual tdco X tdcv Y configure X and Y for tdco and tdcv - tdc-mode auto tdco X configure X tdco and controller measures tdcv automatically - /* nothing */ configure default value for tdco controller measures tdcv automatically The /* nothing */ operation is what the old "ip" tool does, so we're backwards compatible here (using the old "ip" tool on an updated kernel/driver). At first glance it's a bit non-intuitive that you have to specify nothing for the "full" automatic mode. Oh, I just noticed: | ip link set dev mcp251xfd0 down; \ | ip link set mcp251xfd0 txqueuelen 10 up type can \ | sample-point 0.8 bitrate 500000 \ | dsample-point 0.8 dbitrate 2000000 fd on \ | tdc-mode manual tdco 11 tdcv 22 followed by: | ip link set dev mcp251xfd0 down; \ | ip link set mcp251xfd0 txqueuelen 10 up type can We stay in manual mode: | Aug 16 15:27:47 rpi4b8 kernel: mcp251xfd spi0.0 mcp251xfd0: mcp251xfd_set_bittiming: tdco=11 tdcv=22 mode=manual | 8: 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 | tdcv 22 tdco 11 | mcp251xfd: dtseg1 1..32 dtseg2 1..16 dsjw 1..16 dbrp 1..256 dbrp_inc 1 | tdcv 0..63 tdco 0..63 | clock 40000000 numtxqueues 1 numrxqueues 1 gso_max_size 65536 gso_max_segs 65535 parentbus spi parentdev spi0.0 I have to give "fd on" + the bit timing parameters to go to the full automatic mode again: | Aug 16 15:32:46 rpi4b8 kernel: mcp251xfd spi0.0 mcp251xfd0: mcp251xfd_set_bittiming: tdco=16 tdcv=22 mode=automatic Does it make sense to let "mode auto" without a tdco value switch the controller into full automatic mode and /* nothing */ not tough the tdc config at all? If the full automatic mode is power on default mode, then new kernel/drivers are compatible with old the old ip tool. regards, 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 |