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serial: 8250: Auto CTS control by HW if AFE enabled

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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@intel.com>
Signed-off-by: Qipeng Zha <qipeng.zha@intel.com>
Reviewed-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Qipeng Zha 2015-07-29 18:23:32 +08:00 committed by Greg Kroah-Hartman
parent 7d07ada047
commit 0a6c301a2d
2 changed files with 9 additions and 0 deletions
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5
drivers/tty/serial/8250/8250_dw.c
View File

@ -257,6 +257,11 @@ 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);
}

4
drivers/tty/serial/8250/8250_pci.c
View File

@ -1417,6 +1417,10 @@ 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);
}