On 05.05.2023 07:07:03, Thomas.Kopp@xxxxxxxxxxxxx wrote:
> > The datasheet "MCP25xxFD Family Reference Manual" says it needs an idle
> > bus.
>
> Technically what's needed is an idle condition on the bus as specified
> in the ISO. i.e. 11 consecutive sampled recessive bits after a full
> frame (if one is currently in transmission).
Right. What happens if another CAN frames comes before there are 11
consecutive sampled recessive bits? The IFS for CAN is 3 bits?
> > > diff --git a/drivers/net/can/spi/mcp251xfd/mcp251xfd-core.c
> > b/drivers/net/can/spi/mcp251xfd/mcp251xfd-core.c
> > > index 68df6d4641b5c..9908843798cef 100644
> > > --- a/drivers/net/can/spi/mcp251xfd/mcp251xfd-core.c
> > > +++ b/drivers/net/can/spi/mcp251xfd/mcp251xfd-core.c
> > > @@ -227,6 +227,7 @@ static int
> > > __mcp251xfd_chip_set_mode(const struct mcp251xfd_priv *priv,
> > > const u8 mode_req, bool nowait)
> > > {
> > > + const struct can_bittiming *bt = &priv->can.bittiming;
> > > u32 con = 0, con_reqop, osc = 0;
> > > u8 mode;
> > > int err;
> > > @@ -251,7 +252,8 @@ __mcp251xfd_chip_set_mode(const struct
> > mcp251xfd_priv *priv,
> > >
> > FIELD_GET(MCP251XFD_REG_CON_OPMOD_MASK,
> > > con) == mode_req,
> > > MCP251XFD_POLL_SLEEP_US,
> > > - MCP251XFD_POLL_TIMEOUT_US);
> > > + max(MCP251XFD_POLL_TIMEOUT_US,
> > > + 576 * USEC_PER_SEC / bt->bitrate));
> >
> > Let's use CANFD_FRAME_LEN_MAX * BITS_PER_BYTE instead of 576. I can fix
> > this while applying.
> >
> So, I'd suggest CANFD_FRAME_LEN_MAX * BITS_PER_BYTE + 11 + stuffbits,
> as far as I can tell the CANFD_FRAME_LEN_MAX ignores stuffbits, so as
> an overapproximation something like (CANFD_FRAME_LEN_MAX *
> BITS_PER_BYTE) * 1.2 + 11.
..and a define for the 11 and a comment for the * 1.2
> It's unlikely that it will actually be
> necessary but it makes it clear where the numbers are coming from.
Marc
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