tty: max310x: Optionally enable rs485 on startup

UART port might be pre-configured with rs485 enabled flag at the
time of the port starting up process. In this case we need to
have the hardware rs485-related registers initialized in accordance
with the rs485 flags and settings provided by the configs descriptor.

Signed-off-by: Serge Semin <fancer.lancer@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 16 insertions, 0 deletions

diff --git a/drivers/tty/serial/max310x.c b/drivers/tty/serial/max310x.c
index 2255300404bd..36943f6c198c 100644
--- a/drivers/tty/serial/max310x.c
+++ b/drivers/tty/serial/max310x.c
@@ -1030,6 +1030,22 @@ static int max310x_startup(struct uart_port *port)
         max310x_port_update(port, MAX310X_MODE2_REG,
                             MAX310X_MODE2_FIFORST_BIT, 0);
 
+        /* Configure mode1/mode2 to have rs485/rs232 enabled at startup */
+        val = (clamp(port->rs485.delay_rts_before_send, 0U, 15U) << 4) |
+                clamp(port->rs485.delay_rts_after_send, 0U, 15U);
+        max310x_port_write(port, MAX310X_HDPIXDELAY_REG, val);
+
+        if (port->rs485.flags & SER_RS485_ENABLED) {
+                max310x_port_update(port, MAX310X_MODE1_REG,
+                                    MAX310X_MODE1_TRNSCVCTRL_BIT,
+                                    MAX310X_MODE1_TRNSCVCTRL_BIT);
+
+                if (!(port->rs485.flags & SER_RS485_RX_DURING_TX))
+                        max310x_port_update(port, MAX310X_MODE2_REG,
+                                            MAX310X_MODE2_ECHOSUPR_BIT,
+                                            MAX310X_MODE2_ECHOSUPR_BIT);
+        }
+
         /* Configure flow control levels */
         /* Flow control halt level 96, resume level 48 */
         max310x_port_write(port, MAX310X_FLOWLVL_REG,