| Message ID | 20230516101138.24179-1-sherry.sun@nxp.com |
|---|---|
| State | New |
| Headers | show |
| Series | tty: serial: fsl_lpuart: make sure to turn off break before enabling CTS | expand |
Sorry, please ignore this patch, will send another patch to fix the lpuart break issue. Best Regards Sherry > -----Original Message----- > From: Sherry Sun > Sent: 2023年5月16日 18:16 > To: gregkh@linuxfoundation.org; jirislaby@kernel.org > Cc: linux-serial@vger.kernel.org; linux-kernel@vger.kernel.org; dl-linux-imx > <linux-imx@nxp.com> > Subject: [PATCH] tty: serial: fsl_lpuart: make sure to turn off break before > enabling CTS > > Due to one LPUART IP bug which treat the CTS as higher priority than the > break signal, that cause the break signal sending through UARTCTRL_SBK may > impacted by the CTS input if the HW flow control is enabled. > > So commit c4c81db5cf8b ("tty: serial: fsl_lpuart: disable the CTS when send > break signal") try to workaround this IP issue, it disables CTS before asserting > SBK to avoid any interference from CTS, and re-enable it when break off. > > Here we enable CTS before turning off the break, there is still a risk of the > break signal been impacted by CTS input. The correct sequence is to disable > CTS before asserting SBK, and re-enable CTS after break off, which ensures > the break signal won't be impacted by CTS, so fix it. > > Fixes: c4c81db5cf8b ("tty: serial: fsl_lpuart: disable the CTS when send break > signal") > Signed-off-by: Sherry Sun <sherry.sun@nxp.com> > --- > drivers/tty/serial/fsl_lpuart.c | 7 +++---- > 1 file changed, 3 insertions(+), 4 deletions(-) > > diff --git a/drivers/tty/serial/fsl_lpuart.c b/drivers/tty/serial/fsl_lpuart.c > index 0e56fa64b4ce..d9e46f7b80e5 100644 > --- a/drivers/tty/serial/fsl_lpuart.c > +++ b/drivers/tty/serial/fsl_lpuart.c > @@ -1550,20 +1550,19 @@ static void lpuart32_break_ctl(struct uart_port > *port, int break_state) > modem = lpuart32_read(port, UARTMODIR); > > if (break_state != 0) { > - temp |= UARTCTRL_SBK; > /* > * LPUART CTS has higher priority than SBK, need to disable > CTS before > * asserting SBK to avoid any interference if flow control is > enabled. > */ > if (cflag & CRTSCTS && modem & UARTMODIR_TXCTSE) > lpuart32_write(port, modem & > ~UARTMODIR_TXCTSE, UARTMODIR); > + lpuart32_write(port, temp | UARTCTRL_SBK, UARTCTRL); > } else { > - /* Re-enable the CTS when break off. */ > + lpuart32_write(port, temp, UARTCTRL); > + /* Re-enable the CTS after break off. */ > if (cflag & CRTSCTS && !(modem & UARTMODIR_TXCTSE)) > lpuart32_write(port, modem | UARTMODIR_TXCTSE, > UARTMODIR); > } > - > - lpuart32_write(port, temp, UARTCTRL); > } > > static void lpuart_setup_watermark(struct lpuart_port *sport) > -- > 2.17.1
diff --git a/drivers/tty/serial/fsl_lpuart.c b/drivers/tty/serial/fsl_lpuart.c index 0e56fa64b4ce..d9e46f7b80e5 100644 --- a/drivers/tty/serial/fsl_lpuart.c +++ b/drivers/tty/serial/fsl_lpuart.c @@ -1550,20 +1550,19 @@ static void lpuart32_break_ctl(struct uart_port *port, int break_state) modem = lpuart32_read(port, UARTMODIR); if (break_state != 0) { - temp |= UARTCTRL_SBK; /* * LPUART CTS has higher priority than SBK, need to disable CTS before * asserting SBK to avoid any interference if flow control is enabled. */ if (cflag & CRTSCTS && modem & UARTMODIR_TXCTSE) lpuart32_write(port, modem & ~UARTMODIR_TXCTSE, UARTMODIR); + lpuart32_write(port, temp | UARTCTRL_SBK, UARTCTRL); } else { - /* Re-enable the CTS when break off. */ + lpuart32_write(port, temp, UARTCTRL); + /* Re-enable the CTS after break off. */ if (cflag & CRTSCTS && !(modem & UARTMODIR_TXCTSE)) lpuart32_write(port, modem | UARTMODIR_TXCTSE, UARTMODIR); } - - lpuart32_write(port, temp, UARTCTRL); } static void lpuart_setup_watermark(struct lpuart_port *sport)
Due to one LPUART IP bug which treat the CTS as higher priority than the break signal, that cause the break signal sending through UARTCTRL_SBK may impacted by the CTS input if the HW flow control is enabled. So commit c4c81db5cf8b ("tty: serial: fsl_lpuart: disable the CTS when send break signal") try to workaround this IP issue, it disables CTS before asserting SBK to avoid any interference from CTS, and re-enable it when break off. Here we enable CTS before turning off the break, there is still a risk of the break signal been impacted by CTS input. The correct sequence is to disable CTS before asserting SBK, and re-enable CTS after break off, which ensures the break signal won't be impacted by CTS, so fix it. Fixes: c4c81db5cf8b ("tty: serial: fsl_lpuart: disable the CTS when send break signal") Signed-off-by: Sherry Sun <sherry.sun@nxp.com> --- drivers/tty/serial/fsl_lpuart.c | 7 +++---- 1 file changed, 3 insertions(+), 4 deletions(-)