serial: imx: Restore original RXTL for console to fix data loss

Commit 7a637784d517 ("serial: imx: reduce RX interrupt frequency")
introduced a regression on the i.MX6UL EVK board. The issue can be
reproduced with the following steps:

- Open vi on the board.
- Paste a text file (~150 characters).
- Save the file, then repeat the process.
- Compare the sha256sum of the saved files.

The checksums do not match due to missing characters or entire lines.

Fix this by restoring the RXTL value to 1 when the UART is used as a
console.

This ensures timely RX interrupts and reliable data reception in console
mode.

With this change, pasted content is saved correctly, and checksums are
always consistent.

Cc: stable <stable@kernel.org>
Fixes: 7a637784d517 ("serial: imx: reduce RX interrupt frequency")
Signed-off-by: Fabio Estevam <festevam@gmail.com>
Reviewed-by: Stefan Wahren <wahrenst@gmx.net>
Link: https://lore.kernel.org/r/20250619114617.2791939-1-festevam@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/tty/serial/imx.c b/drivers/tty/serial/imx.c
index bd02ee898f5da4481f7d6cbf6fbe9636757e166a..500dfc009d03e8e7f9938168ce62690bedc4d0ae 100644 (file)
--- a/drivers/tty/serial/imx.c
+++ b/drivers/tty/serial/imx.c
@@ -235,6 +235,7 @@ struct imx_port {
        enum imx_tx_state       tx_state;
        struct hrtimer          trigger_start_tx;
        struct hrtimer          trigger_stop_tx;
+       unsigned int            rxtl;
 };
 
 struct imx_port_ucrs {
@@ -1339,6 +1340,7 @@ static void imx_uart_clear_rx_errors(struct imx_port *sport)
 
 #define TXTL_DEFAULT 8
 #define RXTL_DEFAULT 8 /* 8 characters or aging timer */
+#define RXTL_CONSOLE_DEFAULT 1
 #define TXTL_DMA 8 /* DMA burst setting */
 #define RXTL_DMA 9 /* DMA burst setting */
 
@@ -1457,7 +1459,7 @@ static void imx_uart_disable_dma(struct imx_port *sport)
        ucr1 &= ~(UCR1_RXDMAEN | UCR1_TXDMAEN | UCR1_ATDMAEN);
        imx_uart_writel(sport, ucr1, UCR1);
 
-       imx_uart_setup_ufcr(sport, TXTL_DEFAULT, RXTL_DEFAULT);
+       imx_uart_setup_ufcr(sport, TXTL_DEFAULT, sport->rxtl);
 
        sport->dma_is_enabled = 0;
 }
@@ -1482,7 +1484,12 @@ static int imx_uart_startup(struct uart_port *port)
                return retval;
        }
 
-       imx_uart_setup_ufcr(sport, TXTL_DEFAULT, RXTL_DEFAULT);
+       if (uart_console(&sport->port))
+               sport->rxtl = RXTL_CONSOLE_DEFAULT;
+       else
+               sport->rxtl = RXTL_DEFAULT;
+
+       imx_uart_setup_ufcr(sport, TXTL_DEFAULT, sport->rxtl);
 
        /* disable the DREN bit (Data Ready interrupt enable) before
         * requesting IRQs
@@ -1948,7 +1955,7 @@ static int imx_uart_poll_init(struct uart_port *port)
        if (retval)
                clk_disable_unprepare(sport->clk_ipg);
 
-       imx_uart_setup_ufcr(sport, TXTL_DEFAULT, RXTL_DEFAULT);
+       imx_uart_setup_ufcr(sport, TXTL_DEFAULT, sport->rxtl);
 
        uart_port_lock_irqsave(&sport->port, &flags);
 
@@ -2040,7 +2047,7 @@ static int imx_uart_rs485_config(struct uart_port *port, struct ktermios *termio
                /* If the receiver trigger is 0, set it to a default value */
                ufcr = imx_uart_readl(sport, UFCR);
                if ((ufcr & UFCR_RXTL_MASK) == 0)
-                       imx_uart_setup_ufcr(sport, TXTL_DEFAULT, RXTL_DEFAULT);
+                       imx_uart_setup_ufcr(sport, TXTL_DEFAULT, sport->rxtl);
                imx_uart_start_rx(port);
        }
 
@@ -2302,7 +2309,7 @@ imx_uart_console_setup(struct console *co, char *options)
        else
                imx_uart_console_get_options(sport, &baud, &parity, &bits);
 
-       imx_uart_setup_ufcr(sport, TXTL_DEFAULT, RXTL_DEFAULT);
+       imx_uart_setup_ufcr(sport, TXTL_DEFAULT, sport->rxtl);
 
        retval = uart_set_options(&sport->port, co, baud, parity, bits, flow);