korg/linux
0
0
Fork 0
mirror of https://mirrors.bfsu.edu.cn/git/linux.git synced 2025-01-01 11:24:25 +08:00
Code Issues Packages Projects Releases Wiki Activity

tty: serial: fsl_lpuart: avoid idle preamble pending if CTS is enabled

Browse Source 
commit 74cb7e0355 upstream.

If the remote uart device is not connected or not enabled after booting
up, the CTS line is high by default. At this time, if we enable the flow
control when opening the device(for example, using “stty -F /dev/ttyLP4
crtscts” command), there will be a pending idle preamble(first writing 0
and then writing 1 to UARTCTRL_TE will queue an idle preamble) that
cannot be sent out, resulting in the uart port fail to close(waiting for
TX empty), so the user space stty will have to wait for a long time or
forever.

This is an LPUART IP bug(idle preamble has higher priority than CTS),
here add a workaround patch to enable TX CTS after enabling UARTCTRL_TE,
so that the idle preamble does not get stuck due to CTS is deasserted.

Fixes: 380c966c09 ("tty: serial: fsl_lpuart: add 32-bit register interface support")
Cc: stable <stable@kernel.org>
Signed-off-by: Sherry Sun <sherry.sun@nxp.com>
Reviewed-by: Alexander Sverdlin <alexander.sverdlin@siemens.com>
Link: https://lore.kernel.org/r/20240305015706.1050769-1-sherry.sun@nxp.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Sherry Sun 2024-03-05 09:57:06 +08:00 committed by Greg Kroah-Hartman
parent a44c6c61af
commit fed1f00e48
1 changed files with 5 additions and 2 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

7
drivers/tty/serial/fsl_lpuart.c
View File

@ -2237,9 +2237,12 @@ lpuart32_set_termios(struct uart_port *port, struct ktermios *termios,
lpuart32_write(&sport->port, bd, UARTBAUD);
lpuart32_serial_setbrg(sport, baud);
lpuart32_write(&sport->port, modem, UARTMODIR);
lpuart32_write(&sport->port, ctrl, UARTCTRL);
/* disable CTS before enabling UARTCTRL_TE to avoid pending idle preamble */
lpuart32_write(&sport->port, modem & ~UARTMODIR_TXCTSE, UARTMODIR);
/* restore control register */
lpuart32_write(&sport->port, ctrl, UARTCTRL);
/* re-enable the CTS if needed */
lpuart32_write(&sport->port, modem, UARTMODIR);
if (old && sport->lpuart_dma_rx_use) {
if (!lpuart_start_rx_dma(sport))