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tty/serial: atmel: RS485 half duplex w/DMA: enable RX after TX is done

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commit b389f173aaa1204d6dc1f299082a162eb0491545 upstream.

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.

Reported-by: Gil Weber <webergil@gmail.com>
Fixes: 0058f0871efe7b01c6
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>
Signed-off-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>
Tested-by: Bryan Evenson <bevenson@melinkcorp.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Richard Genoud 2016-12-06 13:05:33 +01:00 committed by Greg Kroah-Hartman
parent 8dc821b9f6
commit 990a142ee0
1 changed files with 5 additions and 6 deletions
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11
drivers/tty/serial/atmel_serial.c
View File

@ -810,6 +810,11 @@ static void atmel_complete_tx_dma(void *arg)
*/
if (!uart_circ_empty(xmit))
tasklet_schedule(&atmel_port->tasklet);
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);
}
@ -912,12 +917,6 @@ 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)