STM32MP1 TXINV, RXINV

TX and RX inverter for UART
用途： SBUS


output/build/uboot-custom/arch/arm/mach-stm32mp/include/mach/stm32.h

#ifdef CONFIG_STM32MP15X
#define STM32_USART1_BASE		0x5C000000
#define STM32_USART2_BASE		0x4000E000
#endif
#ifdef CONFIG_STM32MP13X
#define STM32_USART1_BASE		0x4c000000
#define STM32_USART2_BASE		0x4c001000
#endif
#define STM32_USART3_BASE		0x4000F000
#define STM32_UART4_BASE		0x40010000
#define STM32_UART5_BASE		0x40011000
#define STM32_USART6_BASE		0x44003000
#define STM32_UART7_BASE		0x40018000
#define STM32_UART8_BASE		0x40019000

output/build/linux-custom/drivers/tty/serial/stm32-usart.h

#define USART_CR2_SWAP		BIT(15)		/* F7 */
#define USART_CR2_RXINV		BIT(16)		/* F7 */
#define USART_CR2_TXINV		BIT(17)     /* F7 */

output/build/linux-custom/drivers/tty/serial/stm32-usart.c

static int stm32_usart_startup(struct uart_port *port)
{
    struct stm32_port *stm32_port = to_stm32_port(port);
    ...
    ...
    if (stm32_port->swap) {
	val = readl_relaxed(port->membase + ofs->cr2);
	val |= USART_CR2_SWAP;
	writel_relaxed(val, port->membase + ofs->cr2);
    }
    
    //if (!strcmp("4000e000.serial", name))
    if (port->mapbase == 0x4000e000)
    {
	val = readl_relaxed(port->membase + ofs->cr2);
        printk(KERN_ERR "%s, read CR2=0x%x\n", __FUNCTION__, val);
	val |= (USART_CR2_TXINV | USART_CR2_RXINV);
	writel_relaxed(val, port->membase + ofs->cr2);
        printk(KERN_ERR "%s, write CR2=0x%x\n", __FUNCTION__, val);
    }
    ...
    ...
}


static void stm32_usart_set_termios(struct uart_port *port,
				    struct ktermios *termios,
				    const struct ktermios *old)
{
    struct stm32_port *stm32_port = to_stm32_port(port);
    ...
    ...
    cr1 = USART_CR1_TE | USART_CR1_RE;
    if (stm32_port->fifoen)
    cr1 |= USART_CR1_FIFOEN;
    cr2 = stm32_port->swap ? USART_CR2_SWAP : 0;
    
    if (port->mapbase == 0x4000e000)
    {
        cr2 |= (USART_CR2_RXINV | USART_CR2_TXINV);
        pr_info("%s, write CR2=%x\n", __FUNCITON__, cr2);
    }
    ...
    ...
}

ref:
1. 错误之STM32F072CBT6芯片的串口高级功能之反相配置问题(HAL库)
2. 基於stm32和富斯遙控器的SBUS波形分析和通訊實現
3. RF from the TX Line