[expanded Cc: a bit]
Hello Sascha,
On Fri, Jun 14, 2019 at 09:28:01AM +0200, Sascha Hauer wrote:
> The correct setting of the RTS pin depends on the CRTSCTS termios setting:
>
> - When CRTSCTS is disabled then RTS shall be controlled by the TIOCM_RTS
> flag.
> - When CRTSCTS is enabled the expected behaviour of the RTS pin is:
> - When TIOCM_RTS is set then let the receiver control RTS.
> - When the TIOCM_RTS flag is cleared then RTS shall be deasserted (to let
> the upper layers throttle the transfer even when the FIFO in the UART has
> enough space).
>
> This patch fixes this behaviour. Previously the RTS pin has always been
> controlled by the receiver once the TIOCM_RTS flag was set and the CRTSCTS
> setting hasn't been taken into account.
>
> Signed-off-by: Sascha Hauer <s.hauer@xxxxxxxxxxxxxx>
> ---
> drivers/tty/serial/imx.c | 19 +++++++++++++++++--
> 1 file changed, 17 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/tty/serial/imx.c b/drivers/tty/serial/imx.c
> index 8b752e895053..0eddca6455ad 100644
> --- a/drivers/tty/serial/imx.c
> +++ b/drivers/tty/serial/imx.c
> @@ -216,6 +216,7 @@ struct imx_port {
> unsigned int dma_is_enabled:1;
> unsigned int dma_is_rxing:1;
> unsigned int dma_is_txing:1;
> + unsigned int crtscts:1;
> struct dma_chan *dma_chan_rx, *dma_chan_tx;
> struct scatterlist rx_sgl, tx_sgl[2];
> void *rx_buf;
> @@ -967,9 +968,18 @@ static void imx_uart_set_mctrl(struct uart_port *port, unsigned int mctrl)
> u32 ucr2;
>
> ucr2 = imx_uart_readl(sport, UCR2);
> +
> ucr2 &= ~(UCR2_CTS | UCR2_CTSC);
> - if (mctrl & TIOCM_RTS)
> - ucr2 |= UCR2_CTS | UCR2_CTSC;
> +
> + if (mctrl & TIOCM_RTS) {
> + if (sport->crtscts)
> + /* let the receiver control RTS */
> + ucr2 |= UCR2_CTSC;
> + else
> + /* Force RTS active */
> + ucr2 |= UCR2_CTS;
> + }
> +
Other drivers check for
port->status & UPSTAT_AUTORTS
instead of CRTSCTS. I didn't manage to grasp all the details from the
quick look I took, but maybe you should better do the same?
> imx_uart_writel(sport, ucr2, UCR2);
> }
>
> @@ -1554,6 +1564,11 @@ imx_uart_set_termios(struct uart_port *port, struct ktermios *termios,
> else
> ucr2 = UCR2_SRST | UCR2_IRTS;
>
> + if (termios->c_cflag & CRTSCTS)
> + sport->crtscts = true;
> + else
> + sport->crtscts = false;
> +
> if (termios->c_cflag & CRTSCTS) {
I'd put setting sport->crtscts in the following if block, maybe even in
the if (sport->have_rtscts) part that starts below here?
> if (sport->have_rtscts) {
> ucr2 &= ~UCR2_IRTS;
Best regards
Uwe
--
Pengutronix e.K. | Uwe Kleine-König |
Industrial Linux Solutions | http://www.pengutronix.de/ |
