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Date: Fri, 17 Apr 2020 15:15:07 +0200
From: Fabrice Gasnier <fabrice.gasnier@...com>
To: <mani@...nel.org>, <gregkh@...uxfoundation.org>,
<robh+dt@...nel.org>, <mcoquelin.stm32@...il.com>,
<alexandre.torgue@...com>
CC: <linux-serial@...r.kernel.org>, <devicetree@...r.kernel.org>,
<linux-stm32@...md-mailman.stormreply.com>,
<linux-arm-kernel@...ts.infradead.org>,
<linux-kernel@...r.kernel.org>, <andy.shevchenko@...il.com>,
Erwan LE RAY <erwan.leray@...com>
Subject: Re: [PATCH v2 1/2] tty: serial: Add modem control gpio support for
STM32 UART
On 4/16/20 7:57 PM, mani@...nel.org wrote:
> From: Manivannan Sadhasivam <mani@...nel.org>
>
> STM32 UART controllers have the built in modem control support using
> dedicated gpios which can be enabled using 'st,hw-flow-ctrl' flag in DT.
> But there might be cases where the board design need to use different
> gpios for modem control.
>
> For supporting such cases, this commit adds modem control gpio support
> to STM32 UART controller using mctrl_gpio driver.
>
> Signed-off-by: Manivannan Sadhasivam <mani@...nel.org>
> ---
> drivers/tty/serial/Kconfig | 1 +
> drivers/tty/serial/stm32-usart.c | 43 +++++++++++++++++++++++++++++++-
> drivers/tty/serial/stm32-usart.h | 1 +
> 3 files changed, 44 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/tty/serial/Kconfig b/drivers/tty/serial/Kconfig
> index 0aea76cd67ff..e7a6f2130684 100644
> --- a/drivers/tty/serial/Kconfig
> +++ b/drivers/tty/serial/Kconfig
> @@ -1462,6 +1462,7 @@ config SERIAL_STM32
> tristate "STMicroelectronics STM32 serial port support"
> select SERIAL_CORE
> depends on ARCH_STM32 || COMPILE_TEST
> + select SERIAL_MCTRL_GPIO if GPIOLIB
> help
> This driver is for the on-chip Serial Controller on
> STMicroelectronics STM32 MCUs.
> diff --git a/drivers/tty/serial/stm32-usart.c b/drivers/tty/serial/stm32-usart.c
> index 5e93e8d40f59..026982259714 100644
> --- a/drivers/tty/serial/stm32-usart.c
> +++ b/drivers/tty/serial/stm32-usart.c
> @@ -31,6 +31,7 @@
> #include <linux/tty_flip.h>
> #include <linux/tty.h>
>
> +#include "serial_mctrl_gpio.h"
> #include "stm32-usart.h"
>
> static void stm32_stop_tx(struct uart_port *port);
> @@ -510,12 +511,29 @@ static void stm32_set_mctrl(struct uart_port *port, unsigned int mctrl)
> stm32_set_bits(port, ofs->cr3, USART_CR3_RTSE);
> else
> stm32_clr_bits(port, ofs->cr3, USART_CR3_RTSE);
> +
> + mctrl_gpio_set(stm32_port->gpios, mctrl);
> }
>
> static unsigned int stm32_get_mctrl(struct uart_port *port)
> {
> + struct stm32_port *stm32_port = to_stm32_port(port);
> + int ret;
Hi Mani,
Please find few minor remarks and a question from my side.
'ret' could be an unsigned int
> +
> /* This routine is used to get signals of: DCD, DSR, RI, and CTS */
> - return TIOCM_CAR | TIOCM_DSR | TIOCM_CTS;
> + ret = TIOCM_CAR | TIOCM_DSR | TIOCM_CTS;
> +
> + return mctrl_gpio_get(stm32_port->gpios, &ret);
> +}
> +
> +static void stm32_enable_ms(struct uart_port *port)
> +{
Just a question here: purpose of your patch is to handle the gpio case.
So you may get modem control interrupts from gpios with this patch.
In other drivers, I can see the implementation checks gpio usage (like
in atmel_serial). When there's no gpio, the corresponding interrupt at
the serial controller level is enabled, e.g. :
if (!mctrl_gpio_to_gpiod(atmel_port->gpios, UART_GPIO_CTS))
ier |= ...
Do you need modem control interrupts in your case ?
In case the Stinger96 board signals gets fixed in a future revision,
would it be needed to enable modem control interrupts in the USART
controller ?
> + mctrl_gpio_enable_ms(to_stm32_port(port)->gpios);
> +}
> +
> +static void stm32_disable_ms(struct uart_port *port)
> +{
> + mctrl_gpio_disable_ms(to_stm32_port(port)->gpios);
> }
>
> /* Transmit stop */
> @@ -626,6 +644,9 @@ static void stm32_shutdown(struct uart_port *port)
> u32 val, isr;
> int ret;
>
> + /* Disable modem control interrupts */
> + stm32_disable_ms(port);
> +
> val = USART_CR1_TXEIE | USART_CR1_TE;
> val |= stm32_port->cr1_irq | USART_CR1_RE;
> val |= BIT(cfg->uart_enable_bit);
> @@ -764,6 +785,12 @@ static void stm32_set_termios(struct uart_port *port, struct ktermios *termios,
> cr3 |= USART_CR3_CTSE | USART_CR3_RTSE;
> }
>
> + /* Handle modem control interrupts */
> + if (UART_ENABLE_MS(port, termios->c_cflag))
> + stm32_enable_ms(port);
> + else
> + stm32_disable_ms(port);
> +
> usartdiv = DIV_ROUND_CLOSEST(port->uartclk, baud);
>
> /*
> @@ -898,6 +925,7 @@ static const struct uart_ops stm32_uart_ops = {
> .throttle = stm32_throttle,
> .unthrottle = stm32_unthrottle,
> .stop_rx = stm32_stop_rx,
> + .enable_ms = stm32_enable_ms,
> .break_ctl = stm32_break_ctl,
> .startup = stm32_startup,
> .shutdown = stm32_shutdown,
> @@ -964,6 +992,19 @@ static int stm32_init_port(struct stm32_port *stm32port,
> ret = -EINVAL;
return -EINVAL;
> }
>
> + stm32port->gpios = mctrl_gpio_init(&stm32port->port, 0);
> + if (IS_ERR(stm32port->gpios))
Please add error path: add a clk_disable_unprepare() here, before the
return.
> + return PTR_ERR(stm32port->gpios);
> +
> + /* Both CTS/RTS gpios and "st,hw-flow-ctrl" should not be specified */
> + if (stm32port->hw_flow_control) {
> + if (mctrl_gpio_to_gpiod(stm32port->gpios, UART_GPIO_CTS) ||
> + mctrl_gpio_to_gpiod(stm32port->gpios, UART_GPIO_RTS)) {
> + dev_err(&pdev->dev, "Conflicting RTS/CTS config\n");
same here
Best Regards,
Thanks,
Fabrice
> + return -EINVAL;
> + }
> + }
> +
> return ret;
> }
>
> diff --git a/drivers/tty/serial/stm32-usart.h b/drivers/tty/serial/stm32-usart.h
> index db8bf0d4982d..d4c916e78d40 100644
> --- a/drivers/tty/serial/stm32-usart.h
> +++ b/drivers/tty/serial/stm32-usart.h
> @@ -274,6 +274,7 @@ struct stm32_port {
> bool fifoen;
> int wakeirq;
> int rdr_mask; /* receive data register mask */
> + struct mctrl_gpios *gpios; /* modem control gpios */
> };
>
> static struct stm32_port stm32_ports[STM32_MAX_PORTS];
>
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