5.15-stable review patch. If anyone has any objections, please let me know.
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From: Sherry Sun sherry.sun@nxp.com
[ 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 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 Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/tty/serial/fsl_lpuart.c | 17 +++++++++++++++++ 1 file changed, 17 insertions(+)
diff --git a/drivers/tty/serial/fsl_lpuart.c b/drivers/tty/serial/fsl_lpuart.c index fe1fba335483f..6684f6512fb16 100644 --- a/drivers/tty/serial/fsl_lpuart.c +++ b/drivers/tty/serial/fsl_lpuart.c @@ -1397,6 +1397,19 @@ 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 */ @@ -1437,6 +1450,10 @@ 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; }