Re: [PATCH v2 1/2] tty/serial: Add rx-tx-swap OF option to stm32-usart
From: Fabrice Gasnier <fabrice.gasnier@foss.st.com>
Date: 2021-03-01 10:30:45
Also in:
linux-arm-kernel, linux-devicetree, lkml
On 2/27/21 5:41 PM, Martin Devera wrote:
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STM32 F7/H7 usarts supports RX & TX pin swapping. Add option to turn it on. Tested on STM32MP157. Signed-off-by: Martin Devera <redacted> --- 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)
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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
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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 */