From d5bdb37fd02b420cc6a682bf9e51e7e50658c85b Mon Sep 17 00:00:00 2001
From: "GL.iNet-Hongjian.Zhang" <hongjian.zhang@gl-inet.com>
Date: Sat, 18 Sep 2021 14:44:13 +0800
Subject: [PATCH 4/8] add RS485 support

---
 .../821-fix-glinet-rs485-auto-txrx.patch      | 83 +++++++++++++++++++
 1 file changed, 83 insertions(+)
 create mode 100644 target/linux/ath79/patches-5.4/821-fix-glinet-rs485-auto-txrx.patch

diff --git a/target/linux/ath79/patches-5.4/821-fix-glinet-rs485-auto-txrx.patch b/target/linux/ath79/patches-5.4/821-fix-glinet-rs485-auto-txrx.patch
new file mode 100644
index 0000000000..2030cad53d
--- /dev/null
+++ b/target/linux/ath79/patches-5.4/821-fix-glinet-rs485-auto-txrx.patch
@@ -0,0 +1,83 @@
+Index: b/drivers/tty/serial/8250/8250.h
+===================================================================
+--- a/drivers/tty/serial/8250/8250.h	2021-08-26 20:55:22.000000000 +0800
++++ b/drivers/tty/serial/8250/8250.h	2021-09-18 14:30:46.200708724 +0800
+@@ -13,6 +13,8 @@
+ 
+ #include "../serial_mctrl_gpio.h"
+ 
++extern unsigned int rs485txen_gpio;
++
+ struct uart_8250_dma {
+ 	int (*tx_dma)(struct uart_8250_port *p);
+ 	int (*rx_dma)(struct uart_8250_port *p);
+Index: b/drivers/tty/serial/8250/8250_of.c
+===================================================================
+--- a/drivers/tty/serial/8250/8250_of.c	2021-08-26 20:55:22.000000000 +0800
++++ b/drivers/tty/serial/8250/8250_of.c	2021-09-18 14:41:02.964067786 +0800
+@@ -205,6 +205,7 @@ err_pmruntime:
+ /*
+  * Try to register a serial port
+  */
++unsigned int rs485txen_gpio = 0xff;
+ static int of_platform_serial_probe(struct platform_device *ofdev)
+ {
+ 	struct of_serial_info *info;
+@@ -246,6 +247,10 @@ static int of_platform_serial_probe(stru
+ 			&port8250.overrun_backoff_time_ms) != 0)
+ 		port8250.overrun_backoff_time_ms = 0;
+ 
++    if(!of_property_read_u32(ofdev->dev.of_node,"rs485_pin",&rs485txen_gpio)){
++        pr_info("Serial port to 485 enable,rs485txen_gpio = gpio%d \n",rs485txen_gpio);
++    }
++
+ 	ret = serial8250_register_8250_port(&port8250);
+ 	if (ret < 0)
+ 		goto err_dispose;
+Index: b/drivers/tty/serial/8250/8250_port.c
+===================================================================
+--- a/drivers/tty/serial/8250/8250_port.c	2021-08-26 20:55:22.000000000 +0800
++++ b/drivers/tty/serial/8250/8250_port.c	2021-09-18 14:36:49.548608917 +0800
+@@ -34,6 +34,7 @@
+ #include <linux/uaccess.h>
+ #include <linux/pm_runtime.h>
+ #include <linux/ktime.h>
++#include <linux/gpio/consumer.h>
+ 
+ #include <asm/io.h>
+ #include <asm/irq.h>
+@@ -1463,10 +1464,22 @@ static void __stop_tx_rs485(struct uart_
+ 	}
+ }
+ 
++static unsigned int serial8250_tx_empty(struct uart_port *port);
+ static inline void __do_stop_tx(struct uart_8250_port *p)
+ {
+-	if (serial8250_clear_THRI(p))
++    if (serial8250_clear_THRI(p)){
++
+ 		serial8250_rpm_put_tx(p);
++
++        if(0xff != rs485txen_gpio){
++            
++            while(!serial8250_tx_empty(&(p->port))){
++
++                ;
++            }
++            gpiod_set_value(gpio_to_desc(rs485txen_gpio),0);
++        }
++    }
+ }
+ 
+ static inline void __stop_tx(struct uart_8250_port *p)
+@@ -1510,6 +1523,10 @@ static void serial8250_stop_tx(struct ua
+ 
+ static inline void __start_tx(struct uart_port *port)
+ {
++    if(0xff != rs485txen_gpio){
++        gpiod_set_value(gpio_to_desc(rs485txen_gpio),1);
++    }
++
+ 	struct uart_8250_port *up = up_to_u8250p(port);
+ 
+ 	if (up->dma && !up->dma->tx_dma(up))
-- 
2.17.1