On Thu, Sep 14, 2017 at 01:11:33PM +0100, Ian Jamison wrote:
> UART core function uart_update_mctrl relies on a cached value of
> modem control lines. This was used but not updated by local RTS
> control functions within imx.c. These are used for RS485 line
> driver enable signalling. Having an out-of-date value in the cached
> mctrl can result in the transmitter being enabled when it shouldn't
> be.
>
> Fix this by updating the mctrl value before applying it.
>
> Cc: Uwe-Kleine König <u.kleine-koenig@xxxxxxxxxxxxxx>
> Cc: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
> Cc: Clemens Gruber <clemens.gruber@xxxxxxxxxxxx>
> Cc: Fabio Estevam <festevam@xxxxxxxxx>
> Cc: Fabio Estevam <fabio.estevam@xxxxxxx>
> Signed-off-by: Ian Jamison <ian.dev@xxxxxxxxxx>
> ---
> Compile tested only, since my devboard uses a monostable off the TXD
> line to enable the transmitter.
>
> Resending to CC Fabio and Clemens.
>
> drivers/tty/serial/imx.c | 6 ++++--
> 1 file changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/tty/serial/imx.c b/drivers/tty/serial/imx.c
> index dfeff3951f93..3657d745e90f 100644
> --- a/drivers/tty/serial/imx.c
> +++ b/drivers/tty/serial/imx.c
> @@ -334,7 +334,8 @@ static void imx_port_rts_active(struct imx_port *sport, unsigned long *ucr2)
> {
> *ucr2 &= ~(UCR2_CTSC | UCR2_CTS);
>
> - mctrl_gpio_set(sport->gpios, sport->port.mctrl | TIOCM_RTS);
> + sport->port.mctrl |= TIOCM_RTS;
> + mctrl_gpio_set(sport->gpios, sport->port.mctrl);
> }
>
> static void imx_port_rts_inactive(struct imx_port *sport, unsigned long *ucr2)
> @@ -342,7 +343,8 @@ static void imx_port_rts_inactive(struct imx_port *sport, unsigned long *ucr2)
> *ucr2 &= ~UCR2_CTSC;
> *ucr2 |= UCR2_CTS;
>
> - mctrl_gpio_set(sport->gpios, sport->port.mctrl & ~TIOCM_RTS);
> + sport->port.mctrl &= ~TIOCM_RTS;
> + mctrl_gpio_set(sport->gpios, sport->port.mctrl);
> }
>
> static void imx_port_rts_auto(struct imx_port *sport, unsigned long *ucr2)
> --
> 2.14.1
>
Looks good to me. I tested RS-485 communications with this patch applied
between an i.MX6Q board and my host PC (with a RS-485-to-232 converter).
Tested-by: Clemens Gruber <clemens.gruber@xxxxxxxxxxxx>
Cheers,
Clemens
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