On Wed, 2015-07-22 at 23:47 +0800, qipeng.zha wrote:
> 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.
>Have you checked this for ACPI enumerated UART? In that case 8250_dw.c is used and it doesn't have this as well.
Yes, confirmed same issue with 8250_dw.c and update in following patch.
>I also would like to hear Heikki about this.
>
> Signed-off-by: Huiquan Zhong <huiquan.zhong@xxxxxxxxx>
> Signed-off-by: qipeng.zha <qipeng.zha@xxxxxxxxx>
> ---
> drivers/tty/serial/8250/8250_pci.c | 4 ++++
> 1 file changed, 4 insertions(+)
>
> 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); }
>
--
Andy Shevchenko <andriy.shevchenko@xxxxxxxxx> Intel Finland Oy
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