linux-kernel - Re: imx: RS-485 problems during TX, maybe DMA related

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Date:   Sat, 7 Jan 2017 21:59:30 +0100
From:   Clemens Gruber <clemens.gruber@...ruber.com>
To:     Fabio Estevam <festevam@...il.com>
Cc:     linux-serial@...r.kernel.org,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Sascha Hauer <s.hauer@...gutronix.de>,
        Uwe Kleine-König 
        <u.kleine-koenig@...gutronix.de>, Nandor Han <nandor.han@...com>,
        Lucas Stach <l.stach@...gutronix.de>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: imx: RS-485 problems during TX, maybe DMA related

On Sat, Jan 07, 2017 at 02:48:03PM -0200, Fabio Estevam wrote:
> On Sat, Jan 7, 2017 at 1:34 PM, Clemens Gruber
> <clemens.gruber@...ruber.com> wrote:
> > Hi Fabio,
> >
> > On Sat, Jan 07, 2017 at 12:57:10PM -0200, Fabio Estevam wrote:
> >> The MX6QDL_PAD_CSI0_DAT16__UART4_CTS_B option is only valid in dte mode.
> >
> > Ah, the input select is limited in that way, I see.
> >
> > You wrote that you tried rts-gpios.
> > What about setting cts-gpios to gpio6 2 in the DT?
> >
> > Or can you remux RX and TX to be switched to work in dte mode?
> 
> I managed to get RS485 in half-duplex working with rts-gios. Will send
> a patch shortly.

Great!

Did you observe the same effect I described, with the doubling of
characters in the front and the leftovers from previous transmissions at
the end?

Thanks,
Clemens