6.6-stable review patch. If anyone has any objections, please let me know.
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From: Sherry Sun sherry.sun@nxp.com
commit f5cb528d6441eb860250a2f085773aac4f44085e upstream.
According to the LPUART reference manual, TXRTSE and TXRTSPOL of MODIR register only can be changed when the transmitter is disabled. So disable the transmitter before changing RS485 related registers and re-enable it after the change is done.
Fixes: 67b01837861c ("tty: serial: lpuart: Add RS485 support for 32-bit uart flavour") Cc: stable stable@kernel.org Signed-off-by: Sherry Sun sherry.sun@nxp.com Reviewed-by: Frank Li Frank.Li@nxp.com Link: https://lore.kernel.org/r/20250312022503.1342990-1-sherry.sun@nxp.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/tty/serial/fsl_lpuart.c | 17 +++++++++++++++++ 1 file changed, 17 insertions(+)
--- a/drivers/tty/serial/fsl_lpuart.c +++ b/drivers/tty/serial/fsl_lpuart.c @@ -1488,6 +1488,19 @@ static int lpuart32_config_rs485(struct
unsigned long modem = lpuart32_read(&sport->port, UARTMODIR) & ~(UARTMODIR_TXRTSPOL | UARTMODIR_TXRTSE); + u32 ctrl; + + /* TXRTSE and TXRTSPOL only can be changed when transmitter is disabled. */ + ctrl = lpuart32_read(&sport->port, UARTCTRL); + if (ctrl & UARTCTRL_TE) { + /* wait for the transmit engine to complete */ + lpuart32_wait_bit_set(&sport->port, UARTSTAT, UARTSTAT_TC); + lpuart32_write(&sport->port, ctrl & ~UARTCTRL_TE, UARTCTRL); + + while (lpuart32_read(&sport->port, UARTCTRL) & UARTCTRL_TE) + cpu_relax(); + } + lpuart32_write(&sport->port, modem, UARTMODIR);
if (rs485->flags & SER_RS485_ENABLED) { @@ -1507,6 +1520,10 @@ static int lpuart32_config_rs485(struct }
lpuart32_write(&sport->port, modem, UARTMODIR); + + if (ctrl & UARTCTRL_TE) + lpuart32_write(&sport->port, ctrl, UARTCTRL); + return 0; }