CPM2 SCC/SMC break handling broken

[Ricardo Scop]

Hi Laurent,

On Monday 30 October 2006 13:40, Vitaly Bordug wrote:
> On Mon, 30 Oct 2006 16:23:51 +0100
>
> Laurent Pinchart <laurent.pinchart at tbox.biz> wrote:
> > Hi Ricardo,
> >
> > > > > > I need to generate a break on a CPM2 SMC serial port (same issue
> > > > > > with SCC serial ports).
> > > > > >
> > > > > > The tcsendbreak() man page states that the function should
> > > > > > generate a break between 250ms and 500ms, but testing showed that
> > > > > > the break is one character long (10 bits in 8N1 mode).
> > > > >
> > > > > [snip]
> > > > >
> > > > > > CPM_CR_STOP_TX is documented to generate a break of BRKCR
> > > > > > characters. The BRKCR register is initialized to 1, so only 1
> > > > > > break character is sent, which won't last between 250ms and
> > > > > > 500ms.
> > > > >
> > > > > [snip]
> > > > >
> > > > > > Could anyone think of a proper solution which would not disturb
> > > > > > the other drivers too much ?
> > > > >
> > > > > Well, one could always set the BRKCR parameter to the maximum
> > > > > number of break characters permitted by it's size, since the break
> > > > > condition will anyway end as soon as the RESTART TX command is
> > > > > issued as a consequence of the tty->driver->break_ctl(tty, 0) call.
> > > > > But I did not test this.
> > > >
> > > > That's a very good idea, but the documentation is a bit misleading
> > > > here. I tested the CPM2 behaviour, and found out that the break will
> > > > last BRKCR characters, even if a RESTART TX command is sent sooner.
> > > >
> > > > The user manual states
> > > >
> > > > "The SMC sends a programmable number of break characters according to
> > > > BRKCR and reverts to idle or sends data if a RESTART TRANSMIT is
> > > > issued before completion."
> > > >
> > > > I suppose they meant that, if a RESTART TX command is issued before
> > > > completion of the break sequence, the SMC will send data at the end
> > > > of the break sequence. This is at least the behaviour I noticed after
> > > > trying your idea.
> > >
> > > Too bad.... :( One more good idea to the junk bin.
> > >
> > > Hmm, just a wild shot you can try, while you're at that: what about
> > > setting BRKCR to zero and issuing another STOP TRANSMIT, just before
> > > the RESTART TRANSMIT?
> >
> > Wow, congratulations. I wouldn't have thought about that.
Thanks.

BTW, thank you for trying that out. My fingers are much lazier than my brain.

Cheers,

-- 
Ricardo Scop.