* [PATCH] tty/serial: atmel: RS485 half duplex w/DMA: enable RX after TX is done
@ 2016-12-06 12:05 Richard Genoud
2017-01-02 11:53 ` Alexandre Belloni
0 siblings, 1 reply; 4+ messages in thread
From: Richard Genoud @ 2016-12-06 12:05 UTC (permalink / raw)
To: Greg KH
Cc: Gil Weber, Alexandre Belloni, Nicolas Ferre, linux-serial,
linux-kernel, Richard Genoud, stable
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>
---
drivers/tty/serial/atmel_serial.c | 11 +++++------
1 file changed, 5 insertions(+), 6 deletions(-)
diff --git a/drivers/tty/serial/atmel_serial.c b/drivers/tty/serial/atmel_serial.c
index 168b10cad47b..11c0117af80b 100644
--- a/drivers/tty/serial/atmel_serial.c
+++ b/drivers/tty/serial/atmel_serial.c
@@ -798,6 +798,11 @@ static void atmel_complete_tx_dma(void *arg)
*/
if (!uart_circ_empty(xmit))
atmel_tasklet_schedule(atmel_port, &atmel_port->tasklet_tx);
+ else if ((port->rs485.flags & SER_RS485_ENABLED) &&
+ !(port->rs485.flags & SER_RS485_RX_DURING_TX)) {
+ /* DMA done, stop TX, start RX for RS485 */
+ atmel_start_rx(port);
+ }
spin_unlock_irqrestore(&port->lock, flags);
}
@@ -900,12 +905,6 @@ static void atmel_tx_dma(struct uart_port *port)
desc->callback = atmel_complete_tx_dma;
desc->callback_param = atmel_port;
atmel_port->cookie_tx = dmaengine_submit(desc);
-
- } else {
- if (port->rs485.flags & SER_RS485_ENABLED) {
- /* DMA done, stop TX, start RX for RS485 */
- atmel_start_rx(port);
- }
}
if (uart_circ_chars_pending(xmit) < WAKEUP_CHARS)
^ permalink raw reply related [flat|nested] 4+ messages in thread* Re: [PATCH] tty/serial: atmel: RS485 half duplex w/DMA: enable RX after TX is done
2016-12-06 12:05 [PATCH] tty/serial: atmel: RS485 half duplex w/DMA: enable RX after TX is done Richard Genoud
@ 2017-01-02 11:53 ` Alexandre Belloni
2017-01-02 14:14 ` Richard Genoud
0 siblings, 1 reply; 4+ messages in thread
From: Alexandre Belloni @ 2017-01-02 11:53 UTC (permalink / raw)
To: Richard Genoud
Cc: Greg KH, Gil Weber, Nicolas Ferre, linux-serial, linux-kernel,
stable
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
^ permalink raw reply [flat|nested] 4+ messages in thread* Re: [PATCH] tty/serial: atmel: RS485 half duplex w/DMA: enable RX after TX is done
2017-01-02 11:53 ` Alexandre Belloni
@ 2017-01-02 14:14 ` Richard Genoud
2017-01-11 7:09 ` Greg KH
0 siblings, 1 reply; 4+ messages in thread
From: Richard Genoud @ 2017-01-02 14:14 UTC (permalink / raw)
To: Greg KH
Cc: Gil Weber, Nicolas Ferre, linux-serial@vger.kernel.org,
linux-kernel@vger.kernel.org, #4 . 4+, Alexandre Belloni
2017-01-02 12:53 GMT+01:00 Alexandre Belloni
<alexandre.belloni@free-electrons.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>
>
Greg, could you take this patch in your tree ?
^ permalink raw reply [flat|nested] 4+ messages in thread* Re: [PATCH] tty/serial: atmel: RS485 half duplex w/DMA: enable RX after TX is done
2017-01-02 14:14 ` Richard Genoud
@ 2017-01-11 7:09 ` Greg KH
0 siblings, 0 replies; 4+ messages in thread
From: Greg KH @ 2017-01-11 7:09 UTC (permalink / raw)
To: Richard Genoud
Cc: Gil Weber, Nicolas Ferre, linux-serial@vger.kernel.org,
linux-kernel@vger.kernel.org, #4 . 4+, Alexandre Belloni
On Mon, Jan 02, 2017 at 03:14:37PM +0100, Richard Genoud wrote:
> 2017-01-02 12:53 GMT+01:00 Alexandre Belloni
> <alexandre.belloni@free-electrons.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>
> >
> Greg, could you take this patch in your tree ?
Yes, will do so, thanks.
greg k-h
^ permalink raw reply [flat|nested] 4+ messages in thread
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2016-12-06 12:05 [PATCH] tty/serial: atmel: RS485 half duplex w/DMA: enable RX after TX is done Richard Genoud
2017-01-02 11:53 ` Alexandre Belloni
2017-01-02 14:14 ` Richard Genoud
2017-01-11 7:09 ` Greg KH
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