serial: max310x: turn off transmitter before activating AutoCTS or auto transmitter...

As documented in the data-sheet, the transmitter must be disabled before
activating AutoCTS or auto transmitter flow control. Accordingly, the
transmitter must be enabled after AutoCTS or auto transmitter flow
control gets deactivated.

Signed-off-by: Christoph Vogtländer <c.vogtlaender@sigma-surface-science.com>
Link: https://lore.kernel.org/r/20190904121746.4641-1-c.vogtlaender@sigma-surface-science.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/tty/serial/max310x.c b/drivers/tty/serial/max310x.c
index aed19c688beb01d8842a845973e10c6ecab8e4d5..8434bd5a8ec78e1cd1e9f0834b09a5c131845503 100644 (file)
--- a/drivers/tty/serial/max310x.c
+++ b/drivers/tty/serial/max310x.c
@@ -956,6 +956,15 @@ static void max310x_set_termios(struct uart_port *port,
        max310x_port_write(port, MAX310X_XON1_REG, termios->c_cc[VSTART]);
        max310x_port_write(port, MAX310X_XOFF1_REG, termios->c_cc[VSTOP]);
 
+       /* Disable transmitter before enabling AutoCTS or auto transmitter
+        * flow control
+        */
+       if (termios->c_cflag & CRTSCTS || termios->c_iflag & IXOFF) {
+               max310x_port_update(port, MAX310X_MODE1_REG,
+                                   MAX310X_MODE1_TXDIS_BIT,
+                                   MAX310X_MODE1_TXDIS_BIT);
+       }
+
        port->status &= ~(UPSTAT_AUTOCTS | UPSTAT_AUTORTS | UPSTAT_AUTOXOFF);
 
        if (termios->c_cflag & CRTSCTS) {
@@ -974,6 +983,15 @@ static void max310x_set_termios(struct uart_port *port,
        }
        max310x_port_write(port, MAX310X_FLOWCTRL_REG, flow);
 
+       /* Enable transmitter after disabling AutoCTS and auto transmitter
+        * flow control
+        */
+       if (!(termios->c_cflag & CRTSCTS) && !(termios->c_iflag & IXOFF)) {
+               max310x_port_update(port, MAX310X_MODE1_REG,
+                                   MAX310X_MODE1_TXDIS_BIT,
+                                   0);
+       }
+
        /* Get baud rate generator configuration */
        baud = uart_get_baud_rate(port, termios, old,
                                  port->uartclk / 16 / 0xffff,