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tty/serial: atmel: RS485 HD w/DMA: enable RX after TX is stopped
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: b389f173aa
("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>
This commit is contained in:
parent
f304098313
commit
69646d7a36
1 changed files with 21 additions and 3 deletions
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@ -166,6 +166,8 @@ struct atmel_uart_port {
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unsigned int pending_status;
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spinlock_t lock_suspended;
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bool hd_start_rx; /* can start RX during half-duplex operation */
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/* ISO7816 */
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unsigned int fidi_min;
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unsigned int fidi_max;
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@ -933,8 +935,13 @@ static void atmel_complete_tx_dma(void *arg)
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if (!uart_circ_empty(xmit))
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atmel_tasklet_schedule(atmel_port, &atmel_port->tasklet_tx);
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else if (atmel_uart_is_half_duplex(port)) {
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/* DMA done, stop TX, start RX for RS485 */
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atmel_start_rx(port);
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/*
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* DMA done, re-enable TXEMPTY and signal that we can stop
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* TX and start RX for RS485
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*/
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atmel_port->hd_start_rx = true;
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atmel_uart_writel(port, ATMEL_US_IER,
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atmel_port->tx_done_mask);
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}
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spin_unlock_irqrestore(&port->lock, flags);
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@ -1382,9 +1389,20 @@ atmel_handle_transmit(struct uart_port *port, unsigned int pending)
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struct atmel_uart_port *atmel_port = to_atmel_uart_port(port);
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if (pending & atmel_port->tx_done_mask) {
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/* Either PDC or interrupt transmission */
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atmel_uart_writel(port, ATMEL_US_IDR,
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atmel_port->tx_done_mask);
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/* Start RX if flag was set and FIFO is empty */
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if (atmel_port->hd_start_rx) {
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if (!(atmel_uart_readl(port, ATMEL_US_CSR)
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& ATMEL_US_TXEMPTY))
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dev_warn(port->dev, "Should start RX, but TX fifo is not empty\n");
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atmel_port->hd_start_rx = false;
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atmel_start_rx(port);
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return;
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}
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atmel_tasklet_schedule(atmel_port, &atmel_port->tasklet_tx);
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}
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}
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