diff options
| author | Razvan Stefanescu <razvan.stefanescu@microchip.com> | 2019-03-19 15:20:35 +0200 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2019-04-05 22:29:04 +0200 |
| commit | 0668f0d6874088e7fca49c60703e1aa732616d4e (patch) | |
| tree | 69987eef90ec18e93acbf6bb8c4a9ca456db9b37 /drivers/tty/serial | |
| parent | ab18aa0d0c6d07438a098b3d5d285ec4cf4869b8 (diff) | |
tty/serial: atmel: RS485 HD w/DMA: enable RX after TX is stopped
commit 69646d7a3689fbe1a65ae90397d22ac3f1b8d40f upstream.
In half-duplex operation, RX should be started after TX completes.
If DMA is used, there is a case when the DMA transfer completes but the
TX FIFO is not emptied, so the RX cannot be restarted just yet.
Use a boolean variable to store this state and rearm TX interrupt mask
to be signaled again that the transfer finished. In interrupt transmit
handler this variable is used to start RX. A warning message is generated
if RX is activated before TX fifo is cleared.
Fixes: b389f173aaa1 ("tty/serial: atmel: RS485 half duplex w/DMA: enable
RX after TX is done")
Signed-off-by: Razvan Stefanescu <razvan.stefanescu@microchip.com>
Acked-by: Richard Genoud <richard.genoud@gmail.com>
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'drivers/tty/serial')
| -rw-r--r-- | drivers/tty/serial/atmel_serial.c | 24 |
1 files changed, 21 insertions, 3 deletions
diff --git a/drivers/tty/serial/atmel_serial.c b/drivers/tty/serial/atmel_serial.c index 93cb92986395..ef688aadb032 100644 --- a/drivers/tty/serial/atmel_serial.c +++ b/drivers/tty/serial/atmel_serial.c @@ -175,6 +175,8 @@ struct atmel_uart_port { unsigned int pending_status; spinlock_t lock_suspended; + bool hd_start_rx; /* can start RX during half-duplex operation */ + int (*prepare_rx)(struct uart_port *port); int (*prepare_tx)(struct uart_port *port); void (*schedule_rx)(struct uart_port *port); @@ -815,8 +817,13 @@ static void atmel_complete_tx_dma(void *arg) if (!uart_circ_empty(xmit)) atmel_tasklet_schedule(atmel_port, &atmel_port->tasklet_tx); else if (atmel_uart_is_half_duplex(port)) { - /* DMA done, stop TX, start RX for RS485 */ - atmel_start_rx(port); + /* + * DMA done, re-enable TXEMPTY and signal that we can stop + * TX and start RX for RS485 + */ + atmel_port->hd_start_rx = true; + atmel_uart_writel(port, ATMEL_US_IER, + atmel_port->tx_done_mask); } spin_unlock_irqrestore(&port->lock, flags); @@ -1261,9 +1268,20 @@ atmel_handle_transmit(struct uart_port *port, unsigned int pending) struct atmel_uart_port *atmel_port = to_atmel_uart_port(port); if (pending & atmel_port->tx_done_mask) { - /* Either PDC or interrupt transmission */ atmel_uart_writel(port, ATMEL_US_IDR, atmel_port->tx_done_mask); + + /* Start RX if flag was set and FIFO is empty */ + if (atmel_port->hd_start_rx) { + if (!(atmel_uart_readl(port, ATMEL_US_CSR) + & ATMEL_US_TXEMPTY)) + dev_warn(port->dev, "Should start RX, but TX fifo is not empty\n"); + + atmel_port->hd_start_rx = false; + atmel_start_rx(port); + return; + } + atmel_tasklet_schedule(atmel_port, &atmel_port->tasklet_tx); } } |