drivers/serial: add ram uart driver

It uses the memory block as the serial communication medium, which can communicate between different processes or different CPUs

Using the following configuration, the cross-core communication rate of 200MHz cortex-M55 is about 461KB/s
RAM_UART_BUFSIZE=1024
RAM_UART_POLLING_INTERVAL=100

Signed-off-by: yinshengkai <yinshengkai@xiaomi.com>

drivers/drivers_initialize.c

@@ -41,6 +41,7 @@
 #include <nuttx/segger/rtt.h>
 #include <nuttx/sensors/sensor.h>
 #include <nuttx/serial/pty.h>
+#include <nuttx/serial/uart_ram.h>
 #include <nuttx/syslog/syslog.h>
 #include <nuttx/syslog/syslog_console.h>
 #include <nuttx/trace.h>
@@ -118,6 +119,10 @@ void drivers_initialize(void)
   rpmsg_serialinit();
 #endif
 
+#ifdef CONFIG_RAM_UART
+  ram_serialinit();
+#endif
+
   /* Initialize the console device driver (if it is other than the standard
    * serial driver).
    */

drivers/serial/Kconfig

@@ -679,6 +679,75 @@ source "drivers/serial/Kconfig-lpuart"
 source "drivers/serial/Kconfig-usart"
 source "drivers/serial/Kconfig-sci"
 
+config RAM_UART
+	bool "RAM uart driver"
+	select SERIAL_RXDMA
+	select SERIAL_TXDMA
+	default n
+	---help---
+		It uses the memory block in the kernel as a communication medium,
+		which can communicate between different processes or different CPUs
+
+if RAM_UART
+config RAM_UART_POLLING_INTERVAL
+	int "RAM uart buffer check interval"
+	default USEC_PER_TICK
+	---help---
+		Interval in milliseconds to check for new data on uart ram buffer
+
+config RAM_UART_BUFSIZE
+	int "RAM_UART buffer size"
+	default 1024
+	---help---
+		The size of the RAM_UART buffer in bytes
+
+config RAM_UART0
+	bool "RAM uart driver 0"
+	default n
+	---help---
+		RAM_UART device 0
+
+config RAM_UART0_SLAVE
+	bool "RAM_UART0 is slave"
+	depends on RAM_UART0
+	default n
+	---help---
+		The RAM uart0 is slave
+
+config RAM_UART1
+	bool "RAM uart driver 1"
+	default n
+	---help---
+		RAM uart device 1
+
+config RAM_UART1_SLAVE
+	bool "RAM uart1 is slave"
+	depends on RAM_UART1
+	default n
+	---help---
+		The RAM uart1 is slave
+
+config RAM_UART2
+	bool "RAM uart driver 2"
+	default n
+	---help---
+		RAM uart device 2
+
+config RAM_UART2_SLAVE
+	bool "RAM uart2 is slave"
+	depends on RAM_UART2
+	default n
+	---help---
+		The RAM uart2 is slave
+
+config RAM_UART_BUFFER_SECTION
+	string "RAM uart buffer section name"
+	depends on RAM_UART0 || RAM_UART1 || RAM_UART2
+	---help---
+		The name of the section in the kernel memory block
+
+endif # RAM_UART
+
 menuconfig PSEUDOTERM
 	bool "Pseudo-Terminal (PTY) support"
 	default n

drivers/serial/Make.defs

@@ -61,6 +61,11 @@ ifeq ($(CONFIG_UART_BTH5),y)
   CSRCS += uart_bth5.c
 endif
 
+# RAM uart support
+
+ifeq ($(CONFIG_RAM_UART),y)
+  CSRCS += uart_ram.c
+endif
 
 # Include serial build support
 

include/nuttx/serial/uart_ram.h

@@ -0,0 +1,82 @@
+/****************************************************************************
+ * include/nuttx/serial/uart_ram.h
+ *
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.  The
+ * ASF licenses this file to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance with the
+ * License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.  See the
+ * License for the specific language governing permissions and limitations
+ * under the License.
+ *
+ ****************************************************************************/
+
+#ifndef __INCLUDE_NUTTX_SERIAL_UART_RAM_H
+#define __INCLUDE_NUTTX_SERIAL_UART_RAM_H
+
+/****************************************************************************
+ * Included Files
+ ****************************************************************************/
+
+#include <nuttx/config.h>
+
+#ifdef CONFIG_RAM_UART
+
+#include <stdatomic.h>
+#include <stdbool.h>
+
+/****************************************************************************
+ * Pre-processor Definitions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Type Declarations
+ ****************************************************************************/
+
+struct uart_rambuf_s
+{
+    char buffer[CONFIG_RAM_UART_BUFSIZE];
+    atomic_uint wroff;
+    atomic_uint rdoff;
+};
+
+/****************************************************************************
+ * Public Data
+ ****************************************************************************/
+
+/****************************************************************************
+ * Public Function Prototypes
+ ****************************************************************************/
+
+#ifdef __cplusplus
+extern "C"
+{
+#endif
+
+/****************************************************************************
+ * Name: uart_ram_register
+ ****************************************************************************/
+
+int uart_ram_register(FAR const char *devname,
+                      FAR struct uart_rambuf_s buffer[2], bool slave);
+
+/****************************************************************************
+ * Name: ram_serialinit
+ ****************************************************************************/
+
+void ram_serialinit(void);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif
+
+#endif