Re: MPC8260 SCC UART hardware flow control

[Laurent Pinchart <laurent.pinchart@tbox.biz>]

Hi Mathieu,

> > Hi everybody,
> >
> > I was wondering if anyone had implemented hardware flow control support
> > in the cpm_uart driver. If not, I would appreciate pointers regarding how
> > to do so.
> >
> > Best regards,
> >
> > Laurent Pinchart
>
> I had. PQ2 CPM is a dedicated part which handles this aspect for you via
> its microcode. This also means you can't play with it the old way and
> making your own HHS with a CD/DSR :). Back to seriousness, rather this
> means you needn't adding modem signal handling in cpm_uart driver. So don't
> define modem_something that's an ancient reliq from the times, I guess, no
> CPM was put auxillary.
>
> So how to tell CPM to cope with HHS ? Simple, you "just" have to put SCC's
> Dedicated pins the right way which depends on your board type. Remember you
> can't do any HHS with SMC. Refer to Dedicated Pins chapter in the
> litterature [41.4.2]. Also take a look at SCC GSMR register [20.8] and to
> SCC UART mode PSMR register [21-14] to maybe use protocol specificities.

Thanks.

> When you'll have your kernel ready, you would do probably something like :
> 	stty -F $port crtscts $SPEED

I suppose I also have to add support for the CRTSCTS flag in set_termios.

> As Wolfgang said HHS works for DTE-DCE only (roughly but visually you must
> have plugs opposite gender on both ends), trying DTE-DTE HHS dialog is
> bound to failure despite time spend on it.

I'll disable hardware flow control if I need DTE-DTE communication.

Thanks for your help.

Laurent Pinchart