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authorRichard Genoud <richard.genoud@gmail.com>2016-12-06 15:05:33 +0300
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2017-01-11 10:18:45 +0300
commitb389f173aaa1204d6dc1f299082a162eb0491545 (patch)
treed702ef5021258fc6894bec24dcb2e68a06a3c0a5 /drivers/tty/serial/atmel_serial.c
parent89d8232411a85b9a6b12fd5da4d07d8a138a8e0c (diff)
downloadlinux-b389f173aaa1204d6dc1f299082a162eb0491545.tar.xz
tty/serial: atmel: RS485 half duplex w/DMA: enable RX after TX is done
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> 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: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'drivers/tty/serial/atmel_serial.c')
-rw-r--r--drivers/tty/serial/atmel_serial.c11
1 files changed, 5 insertions, 6 deletions
diff --git a/drivers/tty/serial/atmel_serial.c b/drivers/tty/serial/atmel_serial.c
index f9d42de5ab2d..fabbe76203bb 100644
--- a/drivers/tty/serial/atmel_serial.c
+++ b/drivers/tty/serial/atmel_serial.c
@@ -809,6 +809,11 @@ 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);
}
@@ -911,12 +916,6 @@ 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)