linux-kernel - Re: [PATCH v5 2/7] can: bittiming: allow TDC{V,O} to be zero and add can_tdc_const::tdc{v,o,f}

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Date:   Tue, 17 Aug 2021 01:04:15 +0900
From:   Vincent MAILHOL <mailhol.vincent@...adoo.fr>
To:     Marc Kleine-Budde <mkl@...gutronix.de>
Cc:     linux-can <linux-can@...r.kernel.org>,
        Stefan Mätje <Stefan.Maetje@....eu>,
        netdev <netdev@...r.kernel.org>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v5 2/7] can: bittiming: allow TDC{V,O} to be zero and add can_tdc_const::tdc{v,o,f}_min

Hi Marc,

I answered too quickly in one paragraph.

On Tue. 17 Aug 2021 at 00:49, Vincent MAILHOL
<mailhol.vincent@...adoo.fr> wrote:
> On Mon. 16 Aug 2021 at 22:43, Marc Kleine-Budde <mkl@...gutronix.de> wrote:
...
> > 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: <NOARP,UP,LOWER_UP,ECHO> mtu 72 qdisc pfifo_fast state UP mode DEFAULT group default qlen 10
> > |     link/can  promiscuity 0 minmtu 0 maxmtu 0
> > |     can <FD,TDC_AUTO,TDC_MANUAL> state ERROR-ACTIVE (berr-counter tx 0 rx 0) restart-ms 100
>
> That's a bug. It should be impossible to have both TDC_AUTO and
> TDC_MANUAL at the same time.
>
> > |           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
>
> Sorry, but can I confirm what you did here? You stated that you
> did those four commands in this order:
>
> > | 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
>
> So now, you should be in Classical CAN (fd flag off) but the
> results of iproute2 shows that FD is on... Is there one missing
> step?

Please ignore this part. I misread the latest command and thought
you were configuring it as classical CAN. You just did a network
down / up.

I will troubleshoot this tomorrow.

> > 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

Yours sincerely,
Vincent