arch/esp32 add openeth mac driver

This driver is used with QEMU, to make it possible
to use networking.

This is not the MAC in ESP32, however, it can be used with QEMU.

The code was shamelessly copied from https://github.com/espressif/esp-idf/commit/31dac92e5f0daac98190fd603df213a0a25a3807

Documentation/platforms/xtensa/esp32/index.rst

@@ -405,6 +405,13 @@ A QEMU-compatible ``nuttx.merged.bin`` binary image will be created. It can be r
 
  $ qemu-system-xtensa -nographic -machine esp32 -drive file=nuttx.merged.bin,if=mtd,format=raw
 
+QEMU Networking
+---------------
+
+Networking is possible using the openeth MAC driver. Enable ``ESP32_OPENETH`` option and set the nic in QEMU:
+
+ $ qemu-system-xtensa -nographic -machine esp32 -drive file=nuttx.merged.bin,if=mtd,format=raw -nic user,model=open_eth
+
 Secure Boot and Flash Encryption
 ================================
 

arch/xtensa/src/esp32/Kconfig

@@ -241,6 +241,32 @@ config ESP32_EMAC
 	---help---
 		Enable ESP32 ethernet support.
 
+config ESP32_OPENETH
+	bool "Opencores Ethernet MAC"
+	default n
+	depends on !ESP32_EMAC
+	select NET
+	select SCHED_WORKQUEUE
+	---help---
+		Enable ESP32 ethernet opencores support for use with QEMU.
+		Disable this if you are using the real device.
+
+if ESP32_OPENETH
+	config ESP32_OPENETH_DMA_RX_BUFFER_NUM
+		int "Number of Ethernet DMA Rx buffers"
+		range 1 64
+		default 4
+		help
+			Number of DMA receive buffers, each buffer is 1600 bytes.
+
+	config ESP32_OPENETH_DMA_TX_BUFFER_NUM
+		int "Number of Ethernet DMA Tx buffers"
+		range 1 64
+		default 1
+		help
+			Number of DMA transmit buffers, each buffer is 1600 bytes.
+endif
+
 config ESP32_I2C
 	bool
 	default n

arch/xtensa/src/esp32/Make.defs

@@ -255,6 +255,10 @@ EXTRA_LIBS += -lbtdm_app
   endif
 endif
 
+ifeq ($(CONFIG_ESP32_OPENETH),y)
+CHIP_CSRCS += esp32_openeth.c
+endif
+
 #############################################################################
 # Espressif HAL for 3rd Party Platforms
 #############################################################################

boards/xtensa/esp32/esp32-devkitc/src/esp32-devkitc.h

@@ -227,5 +227,18 @@ int board_ws2812_initialize(
 #    endif
 #  endif
 
+/****************************************************************************
+ * Name:  openeth_initialize
+ *
+ * Description:
+ *   This function may called from application-specific logic during its
+ *   to perform board-specific initialization of the Open ETH interface
+ *
+ *
+ ****************************************************************************/
+#ifdef CONFIG_ESP32_OPENETH
+int esp32_openeth_initialize(void);
+#endif
+
 #endif /* __ASSEMBLY__ */
 #endif /* __BOARDS_XTENSA_ESP32_ESP32_DEVKITC_SRC_ESP32_DEVKITC_H */