* [PATCH] tty: serial: Add RS485 RTS GPIO control
@ 2020-07-24 10:14 Marek Vasut
2020-07-24 14:08 ` Fabrice Gasnier
0 siblings, 1 reply; 2+ messages in thread
From: Marek Vasut @ 2020-07-24 10:14 UTC (permalink / raw)
To: linux-serial
Cc: Marek Vasut, Andy Shevchenko, Manivannan Sadhasivam,
Fabrice Gasnier, Greg Kroah-Hartman
While the STM32 does support RS485 drive-enable control within the
UART IP itself, some systems have the drive-enable line connected
to a pin which cannot be pinmuxed as RTS. Add support for toggling
the RTS GPIO line using the modem control GPIOs to provide at least
some sort of emulation.
Signed-off-by: Marek Vasut <marex@denx.de>
Cc: Andy Shevchenko <andy.shevchenko@gmail.com>
Cc: Manivannan Sadhasivam <mani@kernel.org>
Cc: Fabrice Gasnier <fabrice.gasnier@st.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/tty/serial/stm32-usart.c | 9 +++++++++
1 file changed, 9 insertions(+)
diff --git a/drivers/tty/serial/stm32-usart.c b/drivers/tty/serial/stm32-usart.c
index d1c5e536a167..22c8477571ce 100644
--- a/drivers/tty/serial/stm32-usart.c
+++ b/drivers/tty/serial/stm32-usart.c
@@ -34,6 +34,7 @@
#include "serial_mctrl_gpio.h"
#include "stm32-usart.h"
+static void stm32_set_mctrl(struct uart_port *port, unsigned int mctrl);
static void stm32_stop_tx(struct uart_port *port);
static void stm32_transmit_chars(struct uart_port *port);
@@ -129,9 +130,13 @@ static int stm32_config_rs485(struct uart_port *port,
if (rs485conf->flags & SER_RS485_RTS_ON_SEND) {
cr3 &= ~USART_CR3_DEP;
rs485conf->flags &= ~SER_RS485_RTS_AFTER_SEND;
+ stm32_set_mctrl(port,
+ stm32_port->port.mctrl & ~TIOCM_RTS);
} else {
cr3 |= USART_CR3_DEP;
rs485conf->flags |= SER_RS485_RTS_AFTER_SEND;
+ stm32_set_mctrl(port,
+ stm32_port->port.mctrl | TIOCM_RTS);
}
writel_relaxed(cr3, port->membase + ofs->cr3);
@@ -847,9 +852,13 @@ static void stm32_set_termios(struct uart_port *port, struct ktermios *termios,
if (rs485conf->flags & SER_RS485_RTS_ON_SEND) {
cr3 &= ~USART_CR3_DEP;
rs485conf->flags &= ~SER_RS485_RTS_AFTER_SEND;
+ stm32_set_mctrl(port,
+ stm32_port->port.mctrl & ~TIOCM_RTS);
} else {
cr3 |= USART_CR3_DEP;
rs485conf->flags |= SER_RS485_RTS_AFTER_SEND;
+ stm32_set_mctrl(port,
+ stm32_port->port.mctrl | TIOCM_RTS);
}
} else {
--
2.27.0
^ permalink raw reply related [flat|nested] 2+ messages in thread* Re: [PATCH] tty: serial: Add RS485 RTS GPIO control
2020-07-24 10:14 [PATCH] tty: serial: Add RS485 RTS GPIO control Marek Vasut
@ 2020-07-24 14:08 ` Fabrice Gasnier
0 siblings, 0 replies; 2+ messages in thread
From: Fabrice Gasnier @ 2020-07-24 14:08 UTC (permalink / raw)
To: Marek Vasut, linux-serial
Cc: Andy Shevchenko, Manivannan Sadhasivam, Greg Kroah-Hartman,
Alexandre TORGUE, linux-stm32, Erwan LE RAY
On 7/24/20 12:14 PM, Marek Vasut wrote:
> While the STM32 does support RS485 drive-enable control within the
> UART IP itself, some systems have the drive-enable line connected
> to a pin which cannot be pinmuxed as RTS. Add support for toggling
> the RTS GPIO line using the modem control GPIOs to provide at least
> some sort of emulation.
>
> Signed-off-by: Marek Vasut <marex@denx.de>
> Cc: Andy Shevchenko <andy.shevchenko@gmail.com>
> Cc: Manivannan Sadhasivam <mani@kernel.org>
> Cc: Fabrice Gasnier <fabrice.gasnier@st.com>
> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Hi Marek,
You could add stm32 in the commit title.
'git log --oneline' gives "serial: stm32: ..." most of the time here.
Also could you please CC STM32 maintainers and mailing list?
Please find other remark below.
> ---
> drivers/tty/serial/stm32-usart.c | 9 +++++++++
> 1 file changed, 9 insertions(+)
>
> diff --git a/drivers/tty/serial/stm32-usart.c b/drivers/tty/serial/stm32-usart.c
> index d1c5e536a167..22c8477571ce 100644
> --- a/drivers/tty/serial/stm32-usart.c
> +++ b/drivers/tty/serial/stm32-usart.c
> @@ -34,6 +34,7 @@
> #include "serial_mctrl_gpio.h"
> #include "stm32-usart.h"
>
> +static void stm32_set_mctrl(struct uart_port *port, unsigned int mctrl);
> static void stm32_stop_tx(struct uart_port *port);
> static void stm32_transmit_chars(struct uart_port *port);
>
> @@ -129,9 +130,13 @@ static int stm32_config_rs485(struct uart_port *port,
> if (rs485conf->flags & SER_RS485_RTS_ON_SEND) {
> cr3 &= ~USART_CR3_DEP;
> rs485conf->flags &= ~SER_RS485_RTS_AFTER_SEND;
> + stm32_set_mctrl(port,
> + stm32_port->port.mctrl & ~TIOCM_RTS);
Calling stm32_set_mctrl() will also set or clear bit in cr3.
But right after the if() {} else {} statement here there's a:
- writel_relaxed(cr3, port->membase + ofs->cr3);
That's basically overwritten... I guess that's undesired.
So I suggest to simply call mctrl_gpio_set() instead. This is probably
all you need here ?
> } else {
> cr3 |= USART_CR3_DEP;
> rs485conf->flags |= SER_RS485_RTS_AFTER_SEND;
> + stm32_set_mctrl(port,
> + stm32_port->port.mctrl | TIOCM_RTS);
> }
>
> writel_relaxed(cr3, port->membase + ofs->cr3);
> @@ -847,9 +852,13 @@ static void stm32_set_termios(struct uart_port *port, struct ktermios *termios,
> if (rs485conf->flags & SER_RS485_RTS_ON_SEND) {
> cr3 &= ~USART_CR3_DEP;
> rs485conf->flags &= ~SER_RS485_RTS_AFTER_SEND;
> + stm32_set_mctrl(port,
> + stm32_port->port.mctrl & ~TIOCM_RTS);
> } else {
> cr3 |= USART_CR3_DEP;
> rs485conf->flags |= SER_RS485_RTS_AFTER_SEND;
> + stm32_set_mctrl(port,
> + stm32_port->port.mctrl | TIOCM_RTS);
Same as above.
Best Regards,
Fabrice
> }
>
> } else {
>
^ permalink raw reply [flat|nested] 2+ messages in thread
end of thread, other threads:[~2020-07-24 14:08 UTC | newest]
Thread overview: 2+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2020-07-24 10:14 [PATCH] tty: serial: Add RS485 RTS GPIO control Marek Vasut
2020-07-24 14:08 ` Fabrice Gasnier
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).