linux-kernel - [PATCH v2 1/1] serial: 8250_dw: Allow hardware flow control to be used

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Message-Id: <1484164100-9805-2-git-send-email-jason.uy@broadcom.com>
Date:   Wed, 11 Jan 2017 11:48:20 -0800
From:   Jason Uy <jason.uy@...adcom.com>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jiri Slaby <jslaby@...e.com>
Cc:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Kefeng Wang <wangkefeng.wang@...wei.com>,
        Noam Camus <noamc@...hip.com>,
        Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
        Wang Hongcheng <annie.wang@....com>,
        Jason Uy <jason.uy@...adcom.com>, linux-serial@...r.kernel.org,
        linux-kernel@...r.kernel.org, bcm-kernel-feedback-list@...adcom.com
Subject: [PATCH v2 1/1] serial: 8250_dw: Allow hardware flow control to be used

In the most common use case, the Synopsys DW UART driver does not
set the set_termios callback function.  This prevents UPSTAT_AUTOCTS
from being set when the UART flag CRTSCTS is set.  As a result, the
driver will use software flow control as opposed to hardware flow
control.

To fix the problem, the set_termios callback function is set to the
DW specific function.  The logic to set UPSTAT_AUTOCTS is moved so
that any clock error will not affect setting the hardware flow
control.

Reviewed-by: Scott Branden <scott.branden@...adcom.com>
Reviewed-by: Ray Jui <ray.jui@...adcom.com>
Signed-off-by: Jason Uy <jason.uy@...adcom.com>
---
 drivers/tty/serial/8250/8250_dw.c | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/drivers/tty/serial/8250/8250_dw.c b/drivers/tty/serial/8250/8250_dw.c
index c89fafc..c89ae45 100644
--- a/drivers/tty/serial/8250/8250_dw.c
+++ b/drivers/tty/serial/8250/8250_dw.c
@@ -248,11 +248,11 @@ static void dw8250_set_termios(struct uart_port *p, struct ktermios *termios,
 	if (!ret)
 		p->uartclk = rate;
 
+out:
 	p->status &= ~UPSTAT_AUTOCTS;
 	if (termios->c_cflag & CRTSCTS)
 		p->status |= UPSTAT_AUTOCTS;
 
-out:
 	serial8250_do_set_termios(p, termios, old);
 }
 
@@ -326,13 +326,11 @@ static void dw8250_quirks(struct uart_port *p, struct dw8250_data *data)
 			p->serial_in = dw8250_serial_in32;
 			data->uart_16550_compatible = true;
 		}
-		p->set_termios = dw8250_set_termios;
 	}
 
 	/* Platforms with iDMA */
 	if (platform_get_resource_byname(to_platform_device(p->dev),
 					 IORESOURCE_MEM, "lpss_priv")) {
-		p->set_termios = dw8250_set_termios;
 		data->dma.rx_param = p->dev->parent;
 		data->dma.tx_param = p->dev->parent;
 		data->dma.fn = dw8250_idma_filter;
@@ -414,6 +412,7 @@ static int dw8250_probe(struct platform_device *pdev)
 	p->serial_in	= dw8250_serial_in;
 	p->serial_out	= dw8250_serial_out;
 	p->set_ldisc	= dw8250_set_ldisc;
+	p->set_termios	= dw8250_set_termios;
 
 	p->membase = devm_ioremap(dev, regs->start, resource_size(regs));
 	if (!p->membase)
-- 
1.9.1