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tty/serial: atmel_serial: BUG: stop DMA from transmitting in stop_tx

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If we don't disable the transmitter in atmel_stop_tx, the DMA buffer
continues to send data until it is emptied.
This cause problems with the flow control (CTS is asserted and data are
still sent).

So, disabling the transmitter in atmel_stop_tx is a sane thing to do.

Tested on at91sam9g35-cm(DMA)
Tested for regressions on sama5d2-xplained(Fifo) and at91sam9g20ek(PDC)

Cc: <stable@vger.kernel.org> (beware, this won't apply before 4.3)
Signed-off-by: Richard Genoud <richard.genoud@gmail.com>
Acked-by: Nicolas Ferre <nicolas.ferre@atmel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Richard Genoud 2016-12-13 17:27:56 +01:00 committed by Greg Kroah-Hartman
parent a121103c92
commit 89d8232411
1 changed files with 11 additions and 0 deletions
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11
drivers/tty/serial/atmel_serial.c
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@ -481,6 +481,14 @@ static void atmel_stop_tx(struct uart_port *port)
/* disable PDC transmit */
atmel_uart_writel(port, ATMEL_PDC_PTCR, ATMEL_PDC_TXTDIS);
}
/*
* Disable the transmitter.
* This is mandatory when DMA is used, otherwise the DMA buffer
* is fully transmitted.
*/
atmel_uart_writel(port, ATMEL_US_CR, ATMEL_US_TXDIS);
/* Disable interrupts */
atmel_uart_writel(port, ATMEL_US_IDR, atmel_port->tx_done_mask);
@ -513,6 +521,9 @@ static void atmel_start_tx(struct uart_port *port)
/* Enable interrupts */
atmel_uart_writel(port, ATMEL_US_IER, atmel_port->tx_done_mask);
/* re-enable the transmitter */
atmel_uart_writel(port, ATMEL_US_CR, ATMEL_US_TXEN);
}
/*