| From 57eaf84ab643c57e683bfaf46fb9792bc3267fce Mon Sep 17 00:00:00 2001 |
| From: Richard Genoud <richard.genoud@gmail.com> |
| Date: Tue, 6 Dec 2016 13:05:33 +0100 |
| Subject: [PATCH] tty/serial: atmel: RS485 half duplex w/DMA: enable RX after |
| TX is done |
| |
| 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. |
| |
| 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> |
| Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com> |
| |
| diff --git a/drivers/tty/serial/atmel_serial.c b/drivers/tty/serial/atmel_serial.c |
| index 21aeac59df48..dd8fceb246a5 100644 |
| --- a/drivers/tty/serial/atmel_serial.c |
| +++ b/drivers/tty/serial/atmel_serial.c |
| @@ -797,6 +797,11 @@ 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); |
| } |
| @@ -899,12 +904,6 @@ 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) |
| -- |
| 2.10.1 |
| |
