From: "qipeng.zha" <qipeng.zha@xxxxxxxxx> According to DesignWare 8250 spec, if auto flow control mode is enabled, a change in CTS does not cause an interrupt, so sw-assisted CTS flow control mode will not work properly. There reported an GPS firmware download failure issue, and we verified the root cause is, the default sw-assisted CTS flow control mode can not work properly since no interrupt when got CTS signal. This patch is to enable auto CTS mode by defaut if CRTSCTS is enable for DesignWare 8250 controller. Signed-off-by: Huiquan Zhong <huiquan.zhong@xxxxxxxxx> Signed-off-by: Qipeng Zha <qipeng.zha@xxxxxxxxx> --- change in V2: update ACPI enumerated device driver accordingly; --- drivers/tty/serial/8250/8250_dw.c | 5 +++++ drivers/tty/serial/8250/8250_pci.c | 4 ++++ 2 files changed, 9 insertions(+) diff --git a/drivers/tty/serial/8250/8250_dw.c b/drivers/tty/serial/8250/8250_dw.c index 6ae5b85..f78afeb 100644 --- a/drivers/tty/serial/8250/8250_dw.c +++ b/drivers/tty/serial/8250/8250_dw.c @@ -258,6 +258,11 @@ static void dw8250_set_termios(struct uart_port *p, struct ktermios *termios, if (!ret) p->uartclk = rate; + + p->status &= ~UPSTAT_AUTOCTS; + if (termios->c_cflag & CRTSCTS) + p->status |= UPSTAT_AUTOCTS; + out: serial8250_do_set_termios(p, termios, old); } diff --git a/drivers/tty/serial/8250/8250_pci.c b/drivers/tty/serial/8250/8250_pci.c index 892eb32..5aeabe4 100644 --- a/drivers/tty/serial/8250/8250_pci.c +++ b/drivers/tty/serial/8250/8250_pci.c @@ -1438,6 +1438,10 @@ byt_set_termios(struct uart_port *p, struct ktermios *termios, reg |= BYT_PRV_CLK_EN | BYT_PRV_CLK_UPDATE; writel(reg, p->membase + BYT_PRV_CLK); + p->status &= ~UPSTAT_AUTOCTS; + if (termios->c_cflag & CRTSCTS) + p->status |= UPSTAT_AUTOCTS; + serial8250_do_set_termios(p, termios, old); } -- 1.8.3.2 -- To unsubscribe from this list: send the line "unsubscribe linux-serial" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
