From: Alexandre Belloni <alexandre.belloni@free-electrons.com>
To: Richard Genoud <richard.genoud@gmail.com>
Cc: Greg KH <gregkh@linuxfoundation.org>,
Gil Weber <webergil@gmail.com>,
Nicolas Ferre <nicolas.ferre@atmel.com>,
linux-serial@vger.kernel.org, linux-kernel@vger.kernel.org,
stable@vger.kernel.org
Subject: Re: [PATCH] tty/serial: atmel: RS485 half duplex w/DMA: enable RX after TX is done
Date: Mon, 2 Jan 2017 12:53:26 +0100 [thread overview]
Message-ID: <20170102115326.mfly6w5k3dllfpur@piout.net> (raw)
In-Reply-To: <20161206120533.14505-1-richard.genoud@gmail.com>
On 06/12/2016 at 13:05:33 +0100, Richard Genoud wrote :
> When using RS485 in half duplex, RX should be enabled when TX is
> finished, and stopped when TX starts.
>
> Before commit 0058f0871efe7b01c6 ("tty/serial: atmel: fix RS485 half
> duplex with DMA"), RX was not disabled in atmel_start_tx() if the DMA
> was used. So, collisions could happened.
>
> But disabling RX in atmel_start_tx() uncovered another bug:
> RX was enabled again in the wrong place (in atmel_tx_dma) instead of
> being enabled when TX is finished (in atmel_complete_tx_dma), so the
> transmission simply stopped.
>
> This bug was not triggered before commit 0058f0871efe7b01c6
> ("tty/serial: atmel: fix RS485 half duplex with DMA") because RX was
> never disabled before.
>
> Moving atmel_start_rx() in atmel_complete_tx_dma() corrects the problem.
>
> Cc: stable@vger.kernel.org
> Reported-by: Gil Weber <webergil@gmail.com>
> Tested-by: Gil Weber <webergil@gmail.com>
> Signed-off-by: Richard Genoud <richard.genoud@gmail.com>
Acked-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>
--
Alexandre Belloni, Free Electrons
Embedded Linux and Kernel engineering
http://free-electrons.com
next prev parent reply other threads:[~2017-01-02 11:53 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-12-06 12:05 Richard Genoud
2017-01-02 11:53 ` Alexandre Belloni [this message]
2017-01-02 14:14 ` Richard Genoud
2017-01-11 7:09 ` Greg KH
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