Enable XMIT and RCV in all cases when setting RS485 with Atmel serial

1 files changed, 110 insertions, 5 deletions

diff --git a/recipes-kernel/linux/linux-at91-4.9.87/mtcdt/linux-4.9-rs485-atmel-crtscts.patch b/recipes-kernel/linux/linux-at91-4.9.87/mtcdt/linux-4.9-rs485-atmel-crtscts.patch
index 1cf147e..5642aee 100644
--- a/recipes-kernel/linux/linux-at91-4.9.87/mtcdt/linux-4.9-rs485-atmel-crtscts.patch
+++ b/recipes-kernel/linux/linux-at91-4.9.87/mtcdt/linux-4.9-rs485-atmel-crtscts.patch
@@ -2,19 +2,124 @@ This patch allows RS485 Half Duplex (ATMEL_US_USMODE_RS485 is half duplex) to
 work even if handshaking is turned on.  This mimics the behavior of the EXAR
 USB/Serial driver known as Vizzini.  It is impossible to use handshaking when
 using ATMEL_US_USMODE_RS485.  This provides compatibility between MTCDT-0.1 and
-MTCDT-0.2.
+MTCDT-0.2.  Note that frequently the state of the driver will be stopped if
+handshaking was turned on before RS485 was set.  We need to take steps to enable
+transmit and receive when we go to RS485 mode, or the driver will be blocked.
 =======================================================================================
 diff -Naru orig/drivers/tty/serial/atmel_serial.c new/drivers/tty/serial/atmel_serial.c
---- orig/drivers/tty/serial/atmel_serial.c	2021-11-29 12:29:38.472076748 -0600
-+++ new/drivers/tty/serial/atmel_serial.c	2021-11-29 12:26:05.668072459 -0600
-@@ -2171,7 +2171,10 @@
+--- orig/drivers/tty/serial/atmel_serial.c	2021-11-30 14:54:49.313993839 -0600
++++ new/drivers/tty/serial/atmel_serial.c	2021-11-30 16:14:58.430090773 -0600
+@@ -74,6 +74,7 @@
+ 
+ static void atmel_start_rx(struct uart_port *port);
+ static void atmel_stop_rx(struct uart_port *port);
++static void atmel_start_tx(struct uart_port *port);
+ 
+ #ifdef CONFIG_SERIAL_ATMEL_TTYAT
+ 
+@@ -357,6 +358,7 @@
+ {
+ 	struct atmel_uart_port *atmel_port = to_atmel_uart_port(port);
+ 	unsigned int mode;
++	unsigned int sav_c_cflag = 0;
+ 
+ 	/* Disable interrupts */
+ 	atmel_uart_writel(port, ATMEL_US_IDR, atmel_port->tx_done_mask);
+@@ -369,11 +371,33 @@
+ 	port->rs485 = *rs485conf;
+ 
+ 	if (rs485conf->flags & SER_RS485_ENABLED) {
+-		dev_dbg(port->dev, "Setting UART to RS485\n");
+-		atmel_port->tx_done_mask = ATMEL_US_TXEMPTY;
+-		atmel_uart_writel(port, ATMEL_US_TTGR,
++        struct uart_state *state_p = port->state;
++        struct tty_struct *tty_struct_p = NULL;
++
++        dev_dbg(port->dev, "Setting UART to RS485\n");
++        if (state_p)
++           tty_struct_p = state_p->port.tty;
++
++        if(tty_struct_p) {
++           struct ktermios *termios = &(tty_struct_p->termios);
++           sav_c_cflag = termios->c_cflag;
++           termios->c_cflag &= ~CRTSCTS;
++        }
++
++        atmel_port->tx_done_mask = ATMEL_US_TXEMPTY;
++        atmel_uart_writel(port, ATMEL_US_TTGR,
+ 				  rs485conf->delay_rts_after_send);
++        dev_dbg(port->dev,
++           "atmel_config_rs485: orig: c_cflag 0x%x port status 0x%x, hw_stopped %d\n",
++           sav_c_cflag,port->status,port->hw_stopped
++        );
++
++		port->status &= ~UPSTAT_CTS_ENABLE;
+ 		mode |= ATMEL_US_USMODE_RS485;
++		port->hw_stopped = 0;  // No longer possible
++		if (atmel_port->tx_stopped == true)
++            atmel_start_tx(port);
++        atmel_start_rx(port);
+ 	} else {
+ 		dev_dbg(port->dev, "Setting UART to RS232\n");
+ 		if (atmel_use_pdc_tx(port))
+@@ -413,13 +437,36 @@
+ 	unsigned int mode = atmel_uart_readl(port, ATMEL_US_MR);
+ 	unsigned int rts_paused, rts_ready;
+ 	struct atmel_uart_port *atmel_port = to_atmel_uart_port(port);
++        unsigned int sav_c_cflag = 0;
+ 
+ 	/* override mode to RS485 if needed, otherwise keep the current mode */
+ 	if (port->rs485.flags & SER_RS485_ENABLED) {
+-		atmel_uart_writel(port, ATMEL_US_TTGR,
+-				  port->rs485.delay_rts_after_send);
+-		mode &= ~ATMEL_US_USMODE;
+-		mode |= ATMEL_US_USMODE_RS485;
++        struct uart_state *state_p = port->state;
++        struct tty_struct *tty_struct_p = NULL;
++
++        if (state_p)
++            tty_struct_p = state_p->port.tty;
++
++        if(tty_struct_p) {
++            struct ktermios *termios = &(tty_struct_p->termios);
++
++            sav_c_cflag = termios->c_cflag;
++            termios->c_cflag &= ~CRTSCTS;
++        }
++
++        atmel_uart_writel(port, ATMEL_US_TTGR,
++		          port->rs485.delay_rts_after_send);
++        mode &= ~ATMEL_US_USMODE;
++        mode |= ATMEL_US_USMODE_RS485;
++        dev_dbg(port->dev,
++            "atmel_set_mctrl: SER_RS485_ENABLED: c_cflag 0x%x port status 0x%x, hw_stopped %d\n",
++            sav_c_cflag,port->status,port->hw_stopped
++        );
++        port->status &= ~UPSTAT_CTS_ENABLE;
++        port->hw_stopped = 0;  // No longer possible
++        if (atmel_port->tx_stopped == true)
++            atmel_start_tx(port);
++        atmel_start_rx(port);
+ 	}
+ 
+ 	/* set the RTS line state according to the mode */
+@@ -2168,6 +2215,19 @@
  		atmel_uart_writel(port, ATMEL_US_TTGR,
  				  port->rs485.delay_rts_after_send);
  		mode |= ATMEL_US_USMODE_RS485;
 +		/* CRTSCTS is impossible in RS485 mode, and breaks the driver
 +		 * so we cannot do a send. */
++        dev_dbg(port->dev,
++          "atmel_set_termios: SER_RS485_ENABLED: original: c_cflag 0x%x status 0x%x, hw_stopped %d\n",
++          termios->c_cflag,port->status,port->hw_stopped
++        );
++
 +		termios->c_cflag &= ~CRTSCTS;
++        port->status &= ~UPSTAT_CTS_ENABLE;
++		port->hw_stopped = 0; // Not possible
++		if (atmel_port->tx_stopped == true)
++            atmel_start_tx(port);
++        atmel_start_rx(port);
  	} else if (termios->c_cflag & CRTSCTS) {
  		/* RS232 with hardware handshake (RTS/CTS) */
  		if (atmel_use_fifo(port) &&
- 		    !mctrl_gpio_to_gpiod(atmel_port->gpios, UART_GPIO_CTS)) {