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SubjectRe: [PATCH v2 1/2] tty/serial: Add rx-tx-swap OF option to stm32-usart
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On 2/27/21 5:41 PM, Martin Devera wrote:
> STM32 F7/H7 usarts supports RX & TX pin swapping.
> Add option to turn it on.
> Tested on STM32MP157.
>
> Signed-off-by: Martin Devera <devik@eaxlabs.cz>
> ---
> drivers/tty/serial/stm32-usart.c | 3 ++-
> drivers/tty/serial/stm32-usart.h | 1 +
> 2 files changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/tty/serial/stm32-usart.c b/drivers/tty/serial/stm32-usart.c
> index b3675cf25a69..3650c8798061 100644
> --- a/drivers/tty/serial/stm32-usart.c
> +++ b/drivers/tty/serial/stm32-usart.c
> @@ -758,7 +758,7 @@ static void stm32_usart_set_termios(struct uart_port *port,
> cr1 = USART_CR1_TE | USART_CR1_RE;
> if (stm32_port->fifoen)
> cr1 |= USART_CR1_FIFOEN;
> - cr2 = 0;
> + cr2 = stm32_port->swap ? USART_CR2_SWAP : 0;

Hi Martin,

Same could be done in the startup routine, that enables the port for
reception (as described in Documentation/driver-api/serial/driver.rst)

> cr3 = readl_relaxed(port->membase + ofs->cr3);
> cr3 &= USART_CR3_TXFTIE | USART_CR3_RXFTCFG_MASK | USART_CR3_RXFTIE
> | USART_CR3_TXFTCFG_MASK;
> @@ -1078,6 +1078,7 @@ static struct stm32_port *stm32_usart_of_get_port(struct platform_device *pdev)
> stm32_ports[id].hw_flow_control =
> of_property_read_bool (np, "st,hw-flow-ctrl") /*deprecated*/ ||
> of_property_read_bool (np, "uart-has-rtscts");
> + stm32_ports[id].swap = of_property_read_bool(np, "rx-tx-swap");

The swap option/bit is available starting with stm32f7 (e.g. not on
stm32f4).

This could be added to compatible data, e.g. as done for other
capabilities in stm32-usart.h. E.g you could add a "has_swap" in struct
stm32_usart_config, then use it at probe time:
if (cfg->has_swap)
stm32_ports[id].swap = ...;

Thanks for your patch,
Best regards,
Fabrice

> stm32_ports[id].port.line = id;
> stm32_ports[id].cr1_irq = USART_CR1_RXNEIE;
> stm32_ports[id].cr3_irq = 0;
> diff --git a/drivers/tty/serial/stm32-usart.h b/drivers/tty/serial/stm32-usart.h
> index cb4f327c46db..2f054e2dc0ab 100644
> --- a/drivers/tty/serial/stm32-usart.h
> +++ b/drivers/tty/serial/stm32-usart.h
> @@ -271,6 +271,7 @@ struct stm32_port {
> int last_res;
> bool tx_dma_busy; /* dma tx busy */
> bool hw_flow_control;
> + bool swap; /* swap RX & TX pins */
> bool fifoen;
> int wakeirq;
> int rdr_mask; /* receive data register mask */
>

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