From: Sherry Sun Date: Wed, 12 Mar 2025 02:25:03 +0000 (+0800) Subject: tty: serial: fsl_lpuart: disable transmitter before changing RS485 related registers X-Git-Tag: v5.10.236~21 X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=f6c87153c2afc9da65f250990bc47ddf463162d2;p=thirdparty%2Fkernel%2Fstable.git tty: serial: fsl_lpuart: disable transmitter before changing RS485 related registers [ Upstream commit f5cb528d6441eb860250a2f085773aac4f44085e ] 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 Signed-off-by: Sherry Sun Reviewed-by: Frank Li Link: https://lore.kernel.org/r/20250312022503.1342990-1-sherry.sun@nxp.com Signed-off-by: Greg Kroah-Hartman Signed-off-by: Sasha Levin --- diff --git a/drivers/tty/serial/fsl_lpuart.c b/drivers/tty/serial/fsl_lpuart.c index 5135cdc0b6644..110d98fed7260 100644 --- a/drivers/tty/serial/fsl_lpuart.c +++ b/drivers/tty/serial/fsl_lpuart.c @@ -1352,6 +1352,19 @@ static int lpuart32_config_rs485(struct uart_port *port, 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); /* clear unsupported configurations */ @@ -1392,6 +1405,10 @@ static int lpuart32_config_rs485(struct uart_port *port, sport->port.rs485 = *rs485; lpuart32_write(&sport->port, modem, UARTMODIR); + + if (ctrl & UARTCTRL_TE) + lpuart32_write(&sport->port, ctrl, UARTCTRL); + return 0; }