tty/serial: Add rx-tx-swap OF option to stm32-usart

STM32 F7/H7 usarts supports RX & TX pin swapping.
Add option to turn it on.
Tested on STM32MP157.

Acked-by: Fabrice Gasnier <fabrice.gasnier@foss.st.com>
Signed-off-by: Martin Devera <devik@eaxlabs.cz>
Link: https://lore.kernel.org/r/20210328154306.22674-2-devik@eaxlabs.cz
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/tty/serial/stm32-usart.c b/drivers/tty/serial/stm32-usart.c
index cba4f4d..4d27780 100644 (file)
--- a/drivers/tty/serial/stm32-usart.c
+++ b/drivers/tty/serial/stm32-usart.c
@@ -671,6 +671,12 @@ static int stm32_usart_startup(struct uart_port *port)
        if (ret)
                return ret;
 
+       if (stm32_port->swap) {
+               val = readl_relaxed(port->membase + ofs->cr2);
+               val |= USART_CR2_SWAP;
+               writel_relaxed(val, port->membase + ofs->cr2);
+       }
+
        /* RX FIFO Flush */
        if (ofs->rqr != UNDEF_REG)
                writel_relaxed(USART_RQR_RXFRQ, port->membase + ofs->rqr);
@@ -789,7 +795,7 @@ 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;
 
        /* Tx and RX FIFO configuration */
        cr3 = readl_relaxed(port->membase + ofs->cr3);
@@ -1047,6 +1053,9 @@ static int stm32_usart_init_port(struct stm32_port *stm32port,
        stm32port->wakeup_src = stm32port->info->cfg.has_wakeup &&
                of_property_read_bool(pdev->dev.of_node, "wakeup-source");
 
+       stm32port->swap = stm32port->info->cfg.has_swap &&
+               of_property_read_bool(pdev->dev.of_node, "rx-tx-swap");
+
        stm32port->fifoen = stm32port->info->cfg.has_fifo;
 
        res = platform_get_resource(pdev, IORESOURCE_MEM, 0);

diff --git a/drivers/tty/serial/stm32-usart.h b/drivers/tty/serial/stm32-usart.h
index a86773f..77d1ac0 100644 (file)
--- a/drivers/tty/serial/stm32-usart.h
+++ b/drivers/tty/serial/stm32-usart.h
@@ -25,6 +25,7 @@ struct stm32_usart_offsets {
 struct stm32_usart_config {
        u8 uart_enable_bit; /* USART_CR1_UE */
        bool has_7bits_data;
+       bool has_swap;
        bool has_wakeup;
        bool has_fifo;
        int fifosize;
@@ -76,6 +77,7 @@ struct stm32_usart_info stm32f7_info = {
        .cfg = {
                .uart_enable_bit = 0,
                .has_7bits_data = true,
+               .has_swap = true,
                .fifosize = 1,
        }
 };
@@ -97,6 +99,7 @@ struct stm32_usart_info stm32h7_info = {
        .cfg = {
                .uart_enable_bit = 0,
                .has_7bits_data = true,
+               .has_swap = true,
                .has_wakeup = true,
                .has_fifo = true,
                .fifosize = 16,
@@ -268,6 +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;
        bool wakeup_src;
        int rdr_mask;           /* receive data register mask */