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tty: serial: fsl_lpuart: disable transmitter before changing RS485 related registers

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[ 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: 67b0183786 ("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>
This commit is contained in:
Sherry Sun 2025-03-12 10:25:03 +08:00 committed by Greg Kroah-Hartman
parent a824c44e4b
commit bbadf50383
1 changed files with 17 additions and 0 deletions
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17
drivers/tty/serial/fsl_lpuart.c
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@ -1395,6 +1395,19 @@ static int lpuart32_config_rs485(struct uart_port *port, struct ktermios *termio
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) {
@ -1414,6 +1427,10 @@ static int lpuart32_config_rs485(struct uart_port *port, struct ktermios *termio
}
lpuart32_write(&sport->port, modem, UARTMODIR);
if (ctrl & UARTCTRL_TE)
lpuart32_write(&sport->port, ctrl, UARTCTRL);
return 0;
}